08 de octubre de 2023

The Far Eastern Smartweed, Persicaria extremiorientalis is Established in North America

Revised from Atha, D. E., M. H. Nee & R. F. C. Naczi. 2010. Persicaria extremiorientalis (Polygonaceae) is established in the flora of the eastern United States of America. The Journal of the Torrey Botanical Society 137: 333–338. https://doi.org/10.3159/10-RA-033.1

Figure 1. Whole plant (top left): www.inaturalist.org/observations/7877986. Stem internode (top right): www.inaturalist.org/observations/183785156. Flowers and achenes (bottom left): www.inaturalist.org/observations/185228896. Leaf marginal hairs (bottom right): www.inaturalist.org/observations/186240490.

Field work and herbarium study on the genus Persicaria (L.) Mill. revealed a robust, weedy, terrestrial herb reaching 2 m or more in height with pilose stems and purplish, nodding inflorescences that did not fit any species then described in floras or monographs of American Polygonaceae (Meisner 1856, Small 1895, Fernald 1950, Dalci 1974, Gleason and Cronquist 1991, Hinds and Freeman 2005). The species is not described in the Flora of China (Li et al. 2003), but in that work keys out to Polygonum persicaria L. (Persicaria maculosa S. F. Gray). The plant does however, answer to Persicaria extremiorientalis (Vorosch.) Tzvelev as described in the Flora of the Russian Far East (Tzvelev 1989) and Persicaria maculosa subsp. hirticaulis (Danser) S. Ekman and T. Knutsson var. pubescens (Makino) Yonek., pro parte, as described in the Flora of Japan (Yonekura 2006).

The species was first collected in North America by Joseph Vincent Monachino and J. Boxer in Queens and Brooklyn, New York, in 1961 (30 July, Monachino 636; 13 August, Monachino 641; 16 August, Boxer s.n). It was next collected in Stamford, Connecticut on 17 August 1962 by Frank Seymour and B. Wakeman (20311); in Bronx, New York on 26 October 1974 by T. J. Delendick (Delendick s.n.) and then more frequently in the 1980’s, 1990’s and throughout the 2000’s by numerous collectors (principally by staff of the Brooklyn Botanic Garden and The New York Botanical Garden). Most of the specimens were misidentified as Polygonum lapathifolium L. (Persicaria lapathifolia (L.) Delarbre) and/or Polygonum persicaria (Persicaria maculosa), and remained so until the present study.

Many of the approximately 100 species of Persicaria section Persicaria are polyploids, and hybridization is suggested in several instances (Greene 1904, Stanford 1925, Fassett 1949, Timson 1964, Mitchell and Dean 1978, McDonald 1980, Consaul et al. 1991, Kim and Donoghue 2008b). Recent molecular studies document extensive incongruence between sequences in the chloroplast and nuclear genomes, and allopolyploid speciation is suggested for several species (Kim et al. 2008, Kim and Donoghue 2008a, Kim and Donoghue 2008b). Not surprisingly then, there is only weak support for a classification system within Persicaria section Persicaria, and few have been attempted since Meisner’s global monograph of Polygonum s.l. (Meisner 1856).

Uncertain boundaries of individual species and lack of resolution within section Persicaria, combined with the fact that Persicaria extremiorientalis shares character states almost equally with Persicaria lapathifolia and Persicaria maculosa, but also exhibits some not shared by either, argue strongly against recognition as a subspecies and/or variety of either species (as is done in the Flora of Japan).

The binomial Persicaria extremiorientalis is the earliest name unequivocally applicable at the species level for this taxon.

Type specimens and the numerous collections from throughout the range in Asia and eastern North America superficially resemble Persicaria lapathifolia and Persicaria maculosa, but consistently differ from both in several significant characters. The three most consistent character states that distinguish this species from all other Persicaria are: 1, basal stem internodes with appressed hairs; 2, leaf margin setae 0.5–1.1 mm long; and 3, achenes compressed laterally, brown, lustrous and basally tumescent (swollen).

Key to distinguish Persicaria extremiorientalis from the allied Persicaria lapathifolia and Persicaria maculosa

A. Stem internodes glabrous; ocrea outer surfaces glabrous, the apex glabrous; leaf blade margins glabrous or setose with setae , 0.2 mm long, the abaxial surface lanate, arachnoid, or glabrous, glandular-punctate when glabrous; bracts glabrous, the apex caudate or long-acuminate; fruiting tepal vein apices bifurcate and both branches strongly and consistently recurved...........Persicaria lapathifolia.

A. Stem internodes pubescent or glabrous; ocrea outer surfaces strigose, the apex ciliate or setose; leaf blade margins setose, the setae 0.2–1.1 mm long, the abaxial surface strigose, eglandular; bracts sparsely strigose, the apex truncate to obtuse; fruiting tepal vein apices bifurcate or unbranched, if branched, only one branch weakly recurved (never both)...........B.

B. Basal stem internodes glabrous; leaf margin setae 0.2–0.5 mm long; peduncles rarely stipitate-glandular; racemes 1–4 cm long, erect; fruiting tepal veins prominently raised when dry; achenes lenticular or trigonous, basally widest but not tumescent..........Persicaria maculosa.

B. Basal stem internodes with appressed hairs; leaf margin setae 0.5–1.1 mm long; peduncles usually short stipitate glandular; racemes usually 3–8 cm long, usually nodding; fruiting tepal veins not prominently raised when dry; achenes lenticular (rarely trigonous), basally tumescent..........Persicaria extremiorientalis.

Herbs, annual, (0.1–)0.4–2.3 m tall, from slender to stout taproot; stems up to 2 cm diam at the base, proximally unbranched or few-branched, reddish-brown to purple, the proximal and medial stems pilose, rarely glabrate or appressed-setose, the trichomes basally slightly enlarged, distally slender, pale and slightly undulate, 1–5 mm long; ocrea membranous, pale greenish-yellow, somewhat translucent, 12–24 ribbed, the dorsal surface strigose, especially along the ribs, rarely glabrous, 1.3–2.5 cm long, the apices (margins) truncate, setose, the setae 1–5 mm long. Leaves largest proximally, diminishing distally; petioles 1–3 cm long, appressed-setose; blades narrowly ovate, (6–)10–28 3 1–7 cm, the adaxial surface dark green, usually with obscure, but large, central, purple chevron, very regularly and sparsely strigose, the abaxial surface lighter green, evidently eglandular, very regularly (but moderately sparse), golden-strigose, minutely papillose, the base cuneate, the margins entire, appressed-setose, the trichomes arched acroscopically, 0.5–1.1 mm long, the apex long-acuminate; vena- tion pinnate, the abaxial midvein appressed- setose, the trichomes stout, deltoid, the sec- ondary veins arcuate, 12–35 pairs, usually setose. Inflorescences axillary and terminal, leafy; peduncles stipitate-glandular (sometimes the glands very minute or nearly wanting), sometimes also shortly appressed-setose; ra- cemes (1.5–)3–8 cm long, 5–8 mm diam, densely flowered, usually purplish, rarely greenish-white, basally uninterrupted, usually nodding at maturity; bracts ascending, ovate, the dorsal surface sparsely strigose, green- striate, the apices obtuse to acute, setose, the setae ca. 0.2 mm long. Flowers ca. 6 per fascicle-like partial inflorescence, 2 mm long, white at anthesis, soon accrescent and becoming pinkish-purple; pedicels ca. 1.5 mm long, slightly exserted from the bracts; hypanthium 1/5–1/3 length of flower; tepals (4)5, ca. 1 mm long (at anthesis), elliptic, the apices obtuse or rounded, the outer 2 slightly cucullate and slightly exceeding inner, the inner 6 plane; veins trifid-branched above the base, erect, not raised when dry, distally straight and unbranched or rarely and inconsistently bifurcate, one branch then divergent, but not recurved; stamens 5, inserted at the apex of the hypanthium and alternating with the tepals, ca. 0.8 mm long, included; floral glands apparently absent; ovary glabrous, lenticular; styles 2, united about 1/2 the length, distally divergent and slightly recurved, caducous in fruit. Achenes lenticular (rarely trigonous), (1.8–)2.0–2.3 x 1.5–1.9 mm, the faces plane to concave, both faces basally tumescent, the base rounded, the apex obtuse, short-apiculate; pericarp mahogany-brown, lustrous, minutely sculptured.


Very few species of Persicaria have one or two characters that consistently distinguish one species from another; usually a combination of three or more characters is required to distinguish a species. For example, early- blooming or depauperate specimens of Persicaria extremiorientalis have short, erect racemes, like those of Persicaria maculosa. However, the stems will be hirsute (glabrous in Persicaria maculosa) and the leaf blade margins will have setae 0.5 mm long (<0.5 mm in Persicaria maculosa).

Further complicating identification is the fact that several species exhibit extreme variation in gross morphology. The cosmopolitan Persicaria lapathifolia may be ten centimeters tall and have very narrow, eglandular, lanate leaves, or it might be 2 m tall and have wide, glandular, and glabrous leaves. However, both variants will have tepal veins that are distally branched and recurved. There is a seemingly infinite series of intermediates (in habit and leaf characters) spanning the morphological range from one variant to the other (often within a population), but all have glabrous ocrea and inflorescences and have recurved tepal veins.

Persicaria extremiorientalis exhibits a similar broad range of variation in its habit. Early in the season or in marginal habitats, plants are very slender and flower when only 10–20 cm tall. Later in the season and under ideal conditions, they are robust from a stout taproot and flower when two or more meters tall. In habit, Persicaria extremiorientalis strongly resembles Persicaria lapathifolia. In Persicaria extremiorientalis, the central leaf blade adaxial surface in age is pigmented dark purple (unpigmented in Persicaria lapathifolia). It shares the strigose ocrea and bracts with Persicaria maculosa (glabrous in Persicaria lapathifolia). It shares with Persicaria lapathifolia the tendency to have stipitate-glandular peduncles and nodding racemes (eglandular peduncles and erect racemes in Persicaria maculosa). The racemes are usually strongly pigmented pink to purple as in Persicaria maculosa (racemes usually yellow-green or weakly pink tinged in Persicaria lapathifolia). Both Persicaria lapathifolia and Persicaria maculosa have prominent tepal veins, but in Persicaria lapathifolia, they are very prominently raised (when mature and dry), and the apices are always bifurcate with both branches strongly recurved (sometimes called ‘‘anchor veins’’). In Persicaria maculosa the tepal veins are usually prominent, but the apices rarely branch and are never recurved. In Persicaria extremiorientalis the tepal veins may or may not be prominent and sometimes bifurcate, but then only one branch is divergent.

Plants as conspicuous and weedy as the present species would have been noted by prior monographers and collectors, yet no plants like those described here were reported or collected in North America prior to 1961. We therefore hypothesize that the species was introduced sometime shortly before this date. As demonstrated here, the species appears to blend character states from Persicaria lapathifolia and Persicaria maculosa. We hypothesize that Persicaria extremiorientalis is a hybrid of relatively recent origin in eastern Asia, probably involving Persicaria maculosa and Persicaria lapathifolia. Both putative parents are abundant, wide- spread weeds and often co-occur in urban, disturbed, or early successional areas–the same habitats in which American and Asian Persicaria extremiorientalis are found.

Of the numerous populations sampled, none are from undisturbed, climax communities, such as forests, wetlands or grasslands. One of the New York Botanical Garden populations (Atha 6839) consisted of 5 individuals of various sizes in 2008, but throughout the following year and early summer of 2010, none were found at this site.

The Asian congener, Persicaria caespitosa Blume var. longiseta (Bruijn) A. N. Steward was first discovered near Philadelphia in 1910 and by 1940 had spread north to Massachusetts and south to Maryland. By 1991 it was found in every state east of the Mississippi River as well as Nebraska, Iowa, Missouri, Arkansas and Louisiana (Patterson, 2000). These plants invade mesic forests, wetlands, lawns, gardens and waste places throughout the eastern United States, and persist in the same place from year to year, displacing native species. Although Persicaria extremiorientalis appears to be ephemeral from year to year (unlike the persistent Persicaria caespitosa var. longiseta), its spread westward may be expected.

[Addendum October 2023]
The species has now been documented from Maine to South Carolina and west to Akron, Ohio and is probably more widespread than that.

Literature Cited

ATHA, D. E. AND W. CARR. 2010. First report of Persicaria hispida (Polygonaceae) from North America north of Mexico (Texas). J. Bot. Res. Inst. Texas 4: 561–564.

CONSAUL, L. L., S. I. WARWICK, AND J. MCNEILL. 1991. Allozyme variation in the Polygonum lapathifolium complex. Can. J. Bot. 69: 2261–2270.

DALCI, M. 1974. The taxonomy of the section* Persicaria* (Tourn.) L. in the genus Polygonum (Tourn.) L. (Polygonaceae) in the United States east of the Rocky Mountains. Communications de la Facultae des sciences de L’Universitae d’Ankara 18: 133–153.

FASSETT, N. C. 1949. The variation of Polygonum punctatum. Brittonia 6: 369–393.

FERNALD, M. L. 1950. Grays manual of botany. Van Nostrand, New York, NY, USA.

GLEASON, H. A. AND A. CRONQUIST. 1993. Manual of vascular plants of northeastern United States and adjacent Canada (2nd ed). New York Botanical Garden, Bronx, New York, NY, USA.

GREENE, E. L. 1904. Leaflets of botanical observation and criticism. Washington, DC, USA.

HINDS, H. R. AND C. C. FREEMAN. 2005. Persicaria, Pp. 574–594. In Flora of North America Editorial Committee [eds.], Flora of North America North of Mexico 5. Oxford University Press, New York, NY.

KIM, S. T. AND M. J. DONOGHUE. 2008a. Molecular phylogeny of Persicaria (Polygonaceae). Syst. Bot. 33: 77–86.

KIM, S. T. AND M. J. DONOGHUE. 2008b. Incongruence between cpDNA and nrITS trees indicates extensive hybridization within Eupersicaria (Polygonaceae). Am. J. Bot. 95: 1122–1135.

KIM, S. T., S. E. SULTAN, AND M. J. DONOGHUE. 2008. Allopolyploid speciation in *Persicaria (Polygonaceae): Insights from a low-copy nuclear region. Proc. Natl. Acad. Sci. USA. 105: 12370–12375.

LI, A., B. BAO, A. E. GRABOVSKAYA-BORODINA, S-P. HONG, J. MCNEILL, S. L. MOSYAKIN, M. OHBA, AND C. W. PARK. 2003. Polygonaceae. In Wu, Z. Y. and P. H. Raven [eds.], Flora of China 5: 277–350. Missouri Botanical Garden Press, St. Louis, MO.

MCDONALD, C. B. 1980. A biosystematic study of the Polygonum hydropiperoides (Polygonaceae) complex. Am. J. Bot. 67: 664–670.

MEISNER, C. F. 1856. Polygonaceae. In A. de Candolle [ed.], Prodromus systematis naturalis regni vegetabilis 14: 1–186, 693–695. Paris.

MITCHELL, R. S. AND J. K. DEAN. 1978. Polygonaceae (buckwheat family) of New York State. NY State Mus. Bull. 431: 1–79.

PATTERSON, A. K. 2000. Range expansion of Polygonum caespitosum var. longisetum in the United States. Bartonia 60: 57–69.

SMALL, J. K. 1895. A monograph of the North American species of the genus Polygonum. Memoirs from the Department of Botany of Columbia College 1: 1–180.

STANFORD, E. E. 1925. Possibilities of hybridism as a cause of variation in Polygonum. Rhodora 27: 81–89.

TIMSON, J. 1964. A study of hybridization in Polygonum section Persicaria. J. Linnean Soc. 59: 155–160.

TZVELEV, N. N. 1989. ceM. 56. Polygonaceae. Juss., Pp. 25–122. In: Kharkevich, S. S. [ed.], Plantae vasculares Orientis Extremi sovietici [Vascular plants of the Soviet Far East] 4: 1–379. [In Russian].

YONEKURA, K. 2006. Polygonaceae. In K. Iwatsuki, D. E. Boufford, and H. Ohba [eds.], Flora of Japan Vol. II a: 122–174, Kodansha Publ., Tokyo, Japan.

Publicado el octubre 8, 2023 12:08 MAÑANA por danielatha danielatha | 6 comentarios | Deja un comentario

16 de mayo de 2021

Why Confirm the ID When the Observation is Already Research Grade?

Several reasons:

  1. Confirmation by a specialist adds value.
  2. So far, I have found 43 plants misidentified as Sea Grape, Coccoloba uvifera: https://www.inaturalist.org/observations?ident_taxon_id=127284&place_id=any&ident_user_id=20600&without_taxon_id=127284. That's almost one percent of all those I've reviewed. 510 plants misidentified as American Jumpseed, Persicaria virginiana: https://www.inaturalist.org/observations?ident_taxon_id=144047&place_id=any&ident_user_id=20600&without_taxon_id=144047. That's 4.6 percent of the 11,000 I've reviewed.
  3. Of course, I have made a mistake or two myself, but I learn the genus better by seeing many observations.

The same reasons I add annotations confirming identifications on herbarium specimens for species I am familiar with. And in this case, the "annotation" doesn't even take up any real estate on the "specimen".

Publicado el mayo 16, 2021 01:07 MAÑANA por danielatha danielatha | 1 comentario | Deja un comentario

05 de abril de 2021

On the status of Red-Seeded Dandelions (*Taraxacum erythrospermum*)

By Daniel Atha


Everyone knows that trust in science, scientists and scientific institutions is at a low point. It’s not surprising the public is skeptical. The masses have been excluded from the language and practice of science. The public has little say in the goals of science. And many of the products of science have made our world more dangerous and inhospitable.

What I love about natural history is that it is comprehensible to everyone with a desire to look. The natural world is there for everyone to enjoy and study equally. There are no barriers to access and the possibilities for learning are infinite. You don’t need a Hubble telescope or a particle accelerator to study natural history. Nature is the only authority that is never wrong.

As naturalists we know that we would all be better off if more people had a greater appreciation for and understanding of Nature and the earth system processes that make life possible. iNaturalist is democratizing science by empowering everyone to participate in the practice and process of natural history science. Every observation records what we find interesting and meaningful. And the totality of our observations reflect our values individually and collectively.

The literature on species concepts in biology is vast. Generally, most people would agree that a plant species is a lineage that has diverged from a common ancestor and has some genetic and morphological cohesion. The offspring inherit genetic, anatomical and behavioral traits from the parents. Put more simply, a species is a reproductively independent lineage (Rieseberg et al., 2006) with corresponding morphological traits. Disputes arise over reproductive capacity and how well genetic markers (genotype) are correlated with morphological character states (phenotype). See Mayer and the biological species concept (Mayr, 1992).

We might successfully classify a species using one or the other or both genotypic and phenotypic characters without knowing everything about the basic life history and reproductive mechanisms of an organism. In fact, most species are named before a great deal is known about their basic biology. But when either data set or the data in combination are ambiguous, we must seek additional data sets, such as reproductive strategy, chemical productions, chromosome number, etc… See Stewart-Wade et al., 2002 for a broad overview of Taraxacum biology.

It’s also important to remember that science is driven by curiosity and scepticism. When it is based on observable facts and informed by mature and reasoned analysis, science can reveal processes and patterns that may be hidden to the casual observer. The basics of science are the formulation of a hypothesis, testing the hypothesis (including the null hypothesis) and repeatability. Much of what the public thinks of as science deals with abstract concepts and astronomical values. But we must remember that a flora of a given area is really a whole series of hypotheses. Our concept of a species is really just a hypothesis that an organism is definable by a set of traits and that we can tell it apart from others reliably by use of a key. And because we are dealing with plants in the landscape, our floristic hypotheses can be tested by virtually everyone, regardless of their training or prior knowledge. That’s the beauty of a flora and the fun of writing keys.

As scientists (and citizen scientists) we must be careful not to make uninformed judgements or appear overly certain about our interpretations of natural phenomena. In our haste, carelessness or ignorance, we may base a hypothesis on insufficient evidence or poor interpretation of the evidence that is available. In such cases, when the hypothesis is overturned by evidence that should have been considered or analyzed properly, the public’s trust is eroded.

The subject of this post, the common Dandelion, is an example where careful studies carried out by scientists over decades can and should help us interpret and appreciate what we can all see in our lawns and gardens every day-- the common Dandelion. My goal here is to determine (by empirical evidence) whether the Red-Seeded Dandelion is a species as commonly understood by botanists and the public or whether it is a color morph that arises spontaneously from a large pool of genetic variants-- similar to an albino Rat.

Like the common Brown Rat, the Common Dandelion (Taraxacum officinale in the broad sense) is nearly ubiquitous across North America in areas disturbed by humans. The Common Dandelion thrives with ample sun, moisture and nutrients, especially in lawns, garden beds and exposed urban soils.

In North America, nearly all Common Dandelion plants are triploid and apomictic (Lyman and Ellstrand, 1984), meaning that they have three sets of chromosomes and reproduce by parthenogenesis (a process called apomixis whereby seeds are formed without fertilization). In other words, they are clones. Common Dandelions with a “normal” complement of chromosomes (diploid, 2n=16) capable of sexual reproduction with other diploid Dandelions and with triploids (2n=24) are known from Europe, where the species is native. Diploids are extremely rare in North America (Verduijn et al., 2004; Lyman and Ellstrand, 1984) and most plants studied in North America are triploid clones, reproducing asexually by apomixis.

Red-Seeded Dandelions (given the name Taraxacum erythrospermum in 1822 by Antoni Andrzejowski and Joseph Besser.) is treated as a species in most of our floras, including the Flora of North America.

In floristics and systematic botany science, we use taxonomic keys (among other methods) to test our hypotheses. The key is a series of choices that are meant to be mutually exclusive. An organism (taxon) is supposed to fit the characteristics presented in one choice, but not the other. Sometimes key are long and have multiple series of choices that narrow down the options until we are finally presented with just two choices-- one leading to our organisms. Most keys are dichotomous, meaning that each set of questions consists of just two choices, as in the key below.

Every flora treats the "species" in nearly the same way. The detailed descriptions of the two entities (when provided) differ slightly, but the characters in the key here are the ones almost always used to distinguish the species.

A. Leaves usually deeply cut throughout their length, the lobes sharp and narrow, usually pointed back; flower heads smaller; floral bracts (phyllaries) hooded and/or with horns near their tips; seeds (cypselae) reddish or purplish at maturity..... Taraxacum erythrospermum.

A. Leaves less deeply cut, particularly toward the base, the lobes less sharp, not pointed back; flower heads larger; the floral bracts (phyllaries) not hooded and without horns near their tips; seeds (cypselae) brown, olive or tan at maturity..... Taraxacum officinale.

The material presented here demonstrates that these are continuous characters (subject to bias and observer interpretation) and are not correlated with each other or other traits. All research specifically designed to test the hypothesis that Red-Seeded Dandelions are a valid species have found that they are not.

Materials and Methods
Research on the leaf morphology of the Common Dandelions shows that leaf length to width ratio and degree of lobeing varies as the plant ages (Sanchez, 1971) and is influenced by light intensity (Wassink 1965; Sánchez 1967). Rounded leaf blades with less lobeing develop in low light and deeply lobed leaf blades develop in high light (Sánchez 1967; Slabnik 1981). Increasing light intensity increases the leaf lobeing and decreases the leaf length:width ratio (Slabnik 1981). These studies show that the character used by every flora writer to distinguish the two Dandelions (leaf lobeing) is not a trait inherited from the parents, but is rather is a response to environmental variables.

Another study found that achenes actually sort into seven color morphs, but these occur independent of other character states (citation needed).

A study of 20 individuals from several populations across Washington, Oregon, Idaho, Montana, Wyoming, Utah and Nevada representing plants identified as Taraxacum officinale and Taraxacum erythrospermum (Taraxacum laevigatum) found that there was no correlation among twenty-five character states of achenes, involucres, receptacles, leaves and phenolic (chemical) profiles. In fact, these characters showed more variation within populations than between them (Taylor, 1987, citation and abstract below). Achene color-- the single most consistent character state used to distinguish Taraxacum erythrospermum-- was found to be independent of any other character, including shape and degree of leaf lobing. As Taylor points out, it is improbable that the many previous studies have overlooked hitherto untried character combinations to distinguish these entities (e.g. micro-characters). Additionally, as an overwhelmingly asexual, apomictic triploid in North America, it is improbable that hybridization and introgression (back crossing) between putative Taraxacum officinale and Taraxacum erythrospermum has blurred species distinctions creating a continuum of character states bridging one species to the other. Finally, the author’s work and several works cited therein demonstrate a correlation between environmental stress and phenotypic (anatomical) expression including leaf lobing and achene color and that this variation is best explained by a single, weedy species exhibiting a range of phenotypic expression in response to environmental conditions.

Morphological and chemical (phenolic) variables were used in principal components and cluster analyses to determine patterns of variation among and within 22 wide-ranging populations of Dandelions. Intrapopulational morphological variation was as great as or greater than interpopulational variation. Morphological variables were poorly correlated, and plants failed to cluster into the two described species, Taraxacum officinale and Taraxacum laevigatum [Taraxacum erythrospermum]. Phenolic distinctions existed among populations but not between species-types, and chemical variables did not correlate with morphological variables. The data, therefore, suggest that morphological variation is largely due to phenotypic plasticity. This conclusion was supported by the observation of a strong relationship between microhabitat and morphological phenotype, with characteristics of T. laevigatum being expressed under conditions of environmental stress. The pattern of phenolic variability reflects the existence of chemical biotypes. -- Taylor, 1987

Another study of 518 individuals from 22 populations across North America found that there were up to 13 enzyme clonal profiles discernible within a single population of Taraxacum officinale, demonstrating considerable genetic variability within a single population (Lyman and Ellstrand, 1984). In fact, Taraxacum officinale was shown to have a total of 47 enzyme and morphological clonal types among all populations sampled and the highest number of clones per individuals sampled (0.091) of any plant known. By comparison, 108 clonal types have been identified by enzyme analysis for Oenothera laciniata, but only 0.051 clones per individuals sampled. Based on these data and the work of others cited by Lyman and Ellstrand, the authors suggest that multiple introductions of Taraxacum officinale from Europe and Asia have contributed to the high genetic diversity found in North American plants.

In yet another study of 318 Dandelion individuals, Lynn Mertens King found 145 chloroplast (cp) and ribosomal (r) DNA profiles among them. In her work, King states….

"North American dandelions with red achenes do not form a natural group based on either rDNA or cpDNA, so lack of differentiation between North American aggregate species Taraxacum officinale and Taraxacum laevigatum [Taraxacum erythrospermum] in rDNA and cpDNA is consistent with Taylor’s (1987) observations based on morphology and phenolic compounds and suggests they are not separate evolutionary lineages." - King, 1993

Citizen science data from iNaturalist demonstrate that the characters most often used by flora writers to distinguish Taraxacum erythrospermum do not stand up to the test. The characters are: 1. leaf lobeing correlated with achene color; 2. floral bracts (phyllaries) with horn-like appendages correlated with achene color.

The following observations show with empirical evidence that seed (cypselae) color is not consistently correlated with either of these commonly used morphological characters. Rather it appears to occur randomly within populations of "regular" Dandelions. (Field studies here in New York City will be designed to test whether distinctly red seed color occurs randomly in populations and is correlated with any other objective character.)

The following observations were culled from a review of approximately 300 of at least 17,000 global Dandelion observations. https://www.inaturalist.org/observations/identify?page=102&verifiable=true&place_id=any&taxon_id=47602. Observations were reviewed quickly and some which are ambiguous may remain.

Seeds (achenes or cypselae) red but floral bracts (phyllaries) without horns

Seeds red but floral bracts without horns and variable leaves

Red and brown seeded plants growing in mixed populations

Seeds reddish brown

There are many observations with olive colored seeds and with highly divided leaves. Of the observations where you can see both the seeds and the leaves, there are just about as many with olive seeds and highly divided leaves. This is an excellent series of photos with olive achenes, highly divided leaves and phyllaries with small projections. https://www.inaturalist.org/observations/80414881


I have found no scientific studies that support the recognition of Taraxacum erythrospermum as a valid species-- only descriptive accounts using continuous, qualitative characters that are subject to bias. It appears that every study actually testing the validity of the hypothesis with objective and quantitative criteria found that there is no basis for recognition of Taraxacum erythrospermum as a valid species. Don't get me wrong. I love all plants, including the ones we call weeds and invasives. An artificial ranking as species does determine the inherent worth of Red-Seeded Dandelions as living beings worthy of our love and respect.

Based on the evidence presented here, it is clear that the common Dandelion, nearly ubiquitous across North America, is an apomictic, triploid species that has very high rates of morphological, chemical and genetic variability within and among populations, but especially within a population. The author has seen no evidence that the red achene character state is anything but a mutant color morph that may appear randomly wherever clonal Dandelions occur. Until there is convincing evidence for the validity of the species, the available evidence argues for treating the common, weedy Dandelion as a single species (Taraxacum officinale).

This is how science is supposed to work. Someone has a hypothesis. That gets tested independently and objectively and either the evidence supports the hypothesis or doesn't. To ignore the evidence and persist with the unsubstantiated hypothesis is not scientific at all.

Except where explicitly stated, the words and research in this article are entirely my own. The facts belong to everyone. Please acknowledge that you heard it here first.

Literature Cited
King, L.M. 1993. Origins of genotypic variation in North American dandelions inferred from ribosomal DNA and chloroplast DNA restriction enzyme analysis. Evolution 47: 36–151.

Lyman, J.C. and N.C. Ellstrand. 1984. Clonal diversity in Taraxacum officinale Compositae), an apomict. Heredity 53: 1–10.

Mayr, E. 1992. A local flora and the biological species concept. American Journal of botany 79: 1537–2197 https://bsapubs.onlinelibrary.wiley.com/doi/abs/10.1002j.1537-2197.1992.tb13641.x

Riesberg, L., T.E. Wood and E.J. Baack. 2006. The nature of plant species. Nature 440: 24–527. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2443815/

Solbrig, O.T. 1971. The population biology of dandelions. Am. Sci. 59: 686–694.

Solbrig. 0.T. and B.B. Simpson. 1974. Components of regulation of a population of dandelions in Michigan. J. Ecol 62: 473–486.

Solbrig. 0.T. and B.B. Simpson. 1977. A garden experiment on competition between biotypes of the common dandelion (Taraxacum officinale). J. Ecol. 65: 427–430.

Stewart-Wade, S., S. Neumann, L. Collins and G. Boland. The biology of Canadian weeds. 117. Taraxacum officinale G.H. Weber ex Wiggers. Canadian Journal of Plant Science 82: 825–853.

Taylor, R.J. 1987. Populational variation and biosystematic interpretations in weedy dandelions. Bulletin of the Torrey Botanical Club 114: 109–120.

Verduijn, M., P. Van Dijk & J. Van Damme. 2004. The role of tetraploids in the sexual–sexual cycle in dandelions (Taraxacum). Heredity 93: 390–398. https://doi.org/10.1038/sj.hdy.6800515

Wassink, E.C. 1965. Some Introductory Notes on Taraxacum officinale L. as an experimental plant for morphogenetic and production research. Mededelingen Van De Landbouwhogeschool, 65–16. Wageningen: Veenman.

Publicado el abril 5, 2021 11:30 TARDE por danielatha danielatha | 5 comentarios | Deja un comentario

30 de enero de 2021

Daniel's iNat Tips and Tricks

Most of these are URLs coded by others that I think are neat and modified for my interest. Some were coded by me mostly through experimentation with combinations of other bits of code. I am NOT a programmer.

My hierarchical iNaturalist life list

Tony Iwane's iNaturalist search tips

Tips and tricks compiled by others


My yearly stats

Observations in a 48 kilometer (30 mile) radius around City Hall, New York, New York

All White Snakeroot observations in New York City

All Shaggy Soldier and Gallant Soldier in the world

All Cyperus observations in Delaware, Maryland, Pennsylvania, New Jersey and New York

Map of Spicebush and Spicebush Swallowtail Butterfly in NYC

Species observed in New York City by others but not by me

Observations in a 30 mile radius around City Hall, NY that need identification

My identification stats

My identifications of a particular species

My identification differs from community id (for Common Reed)

My identifications of Sea Grape from API with any potential disagreements

North American Persicaria observations I have reviewed at least once, but have not identified.

Common responses

Any comment containing “Smartweed”

Comments by me

Comments that tag me

Comments by me containing “Smartweed”

Comments on my observations

New York City White Snakeroot with Leaf Miner annotation

with Leaf Miner annotation = Yes

with Leaf Miner annotation = No

with Leaf Miner annotation = Unclear

with Leaf Miner annotation = null

How to mark an observation captive/cultivated in the mobile app.

Publicado el enero 30, 2021 12:42 MAÑANA por danielatha danielatha | 0 comentarios | Deja un comentario

18 de diciembre de 2020

Community Scientists Make Important Discoveries

Community scientists make important plant discoveries around New York City

December 2020

New York City EcoFlora community scientists recently discovered two plant species never before documented in our region. Local residents Susan Hewitt, Sara Rall and Zihao Wang discovered a new plant for North America and a new species (and genus) for New York State. They made the discoveries this fall while observing the flora and fauna in the greater New York City region. Their discoveries are published in the latest issue of the online botanical journal, Phytoneuron.

On September 7, 2020, Sara Rall, self-taught naturalist and a resident of New Jersey observed an unusual Smartweed growing in the floodplain of the Delaware River and made note of its distinct features. And by the most improbable coincidence, Daniel Atha observed the same species on the very same day, just hours apart, but 85 miles north on the upper reaches of the Delaware River in Sullivan County, New York. That evening, noting each other's observations on iNaturalist, the two started a conversation about the plants and their unusual features. Herbarium specimens of the New York plants were used to compare with known North American species and possible introductions. A match was eventually found in the Flora of China and the Flora of Taiwan: Persicaria posumbu, a species heretofore never found anywhere in North America. This significant finding is published today in the online botanical journal, Phytoneuron. See: First Report of Persicaria posumbu (Polygonaceae) for North America.
Susan Hewitt, resident of Manhattan and the most prolific observer of plants and animals in New York City and Zihao Wang, resident of Brooklyn, environmental engineer and discoverer of numerous rare plants and animals in the New York City area, independently discovered populations of Tropic Croton, Croton glandulosus, a member of the Spurge family (Euphorbiaceae): Wang in Queens in the fall of 2019 and Hewitt in Manhattan in September 2020. They posted their observations to iNaturalist and their identifications were confirmed by Nathan Taylor, the Euphorbiaceae specialist. Noting the significance of the discoveries for the region, Daniel Atha visited both sites and confirmed that the plants were indeed a new addition to the flora of New York State. Just in time for the holidays, Tropic Croton is closely related to the Pointsettia we all know. Read more about their discovery published today in the online botanical journal Phytoneuron: First Report of Croton glandulosus (Polygonaceae) for New York.
Publicado el diciembre 18, 2020 03:10 TARDE por danielatha danielatha | 11 comentarios | Deja un comentario

16 de noviembre de 2020

Yams (Dioscorea) of Northeastern North America

Wild Yam, Dioscorea villosa Chinese Yam, Dioscorea polystachya

Key to the Dioscorea Species of Northeastern North America

1a. Vine from rhizomes; leaf axils without aerial tubers; mature petioles nearly circular in cross section; leaves ovate-cordate, the sides evenly convex, basal lobes absent; fruits winged..... Dioscorea villosa

1b. Vine from woody tuber; leaf axils often with aerial tubers; mature petioles strongly channeled; leaves hastate, sides with some concavity, basal lobes usually present; fruits unknown in North America..... Dioscorea polystachya

Dioscorea polystachya Turcz. – Chinese Yam, Cinnamon Vine
Introduced; NYS Prohibited; present in NYC. Description. iNaturalist observations from New York City. GloBI interactions.
Indiana non-native plant invasiveness ranking form. Pest Risk Management Document for Dioscorea polystachya (Chinese yam) in Canada

Dioscorea villosa L. – Wild Yam
Indigenous; (CoC 6); present in NYC. Description. iNaturalist observations from New York City. GloBI interactions.

Publicado el noviembre 16, 2020 06:11 TARDE por danielatha danielatha | 2 comentarios | Deja un comentario

29 de octubre de 2020

NYBG Science, Conservation and Humanities Webinars

Everyone is invited to these free Science, Conservation and Humanities Webinars from NYBG

Conserving the Rare Plants of New York (Friday, Nov. 6)

First Nations: Ethical Landscapes, Sacred Plants (Friday, Nov.13)

Here Today, Gone Tomorrow: Plant Extinction Now and Conservation Strategies for Tomorrow (Tuesdays, Nov. 17 & 24):

Sign-up to hear about upcoming NYBG Science, Conservation, and Humanities seminars.

Publicado el octubre 29, 2020 09:15 TARDE por danielatha danielatha | 0 comentarios | Deja un comentario

26 de octubre de 2020

American and Asian Jumpseed in North America

Asian Jumpseed, Persicaria filiformis

Cultivars of the Asian Jumpseed, Persicaria filiformis ‘Painter’s Palette’, ‘Lance Corporal’, ‘Variegata’ and ‘Bat Wings’ are escaping from cultivation in the eastern United States and becoming naturalized. As early as 2017 and 2018, I noted many escapes in the Washington, DC area and began alerting people then to the nomenclatural issues, how to identify it and it's serious invasive potential. It has since spread more widely and become a serious pest in several areas of the northeast.

Morphologically, Persicaria filiformis and its cultivars can be distinguished from the American species Persicaria virginiana by the elliptic leaves that are widest at or above the middle and with persistent purple markings, whereas Persicaria virginiana has ovate leaves, widest below the middle and purple markings only on young leaves. There are other subtle differences one can learn with practice. The American Jumpseed occasionally has pink flowers, so that alone is not enough to distinguish the species.

These introduced, artificial hybrids may interbreed with the indigenous Persicaria virginiana, eroding its genetic integrity and possibly compromising fitness and survival of this important indigenous American plant. The aggressive growth of the Asian Jumpseed also threatens other biodiversity by forming large, monocultural stands that crowd out other species.

Persicaria filiformis (Thunb.) Nakai, Asian Jumpseed is sister to the American Jumpseed. They may share a common ancestor, but millenia of isolation, drifting continents and changing vegetation patterns caused the two species to diverge genetically, anatomically and chemically. But some taxonomists don't consider these differences enough to divide the species and treat them as two varieties of one species or just one species (under the oldest name, Persicaria virginiana). The one-species concept prevailed several decades ago and is often used in older literature and in the horticulture trade. Today there is ample data from multiple lines of evidence and strong support for separating the two as distinct species (Park et al., 1992; Mun & Park, 1995; Suh et al., 1997).

American Jumpseed, Persicaria virginiana

Persicaria virginiana (L.) Gaertn. American Jumpseed is a perennial herb to 1.5 m tall, from knotty rhizomes; stems are erect, slender and few-branched; ocreae strigose or tomentose, the apices ciliate; leaf blades ovate, 5–17 × 2–10 cm, reduced apically, the bases rounded, the apices acute to acuminate, strigose above and below, the margins setose; inflorescences to 45 cm long, very slender; flowers solitary or 2–3 per ocreolate fascicle; tepals 4, white, greenish white or rarely pink; achenes brown with hooked, persistent style. 2n=44.

The species is found across the eastern United States (and southern Canada), east of the 100th meridian, from southern Minnesota to Texas and Quebec to Florida, disjunct in central Mexico; found in rich deciduous forests, floodplain forests, dry woodlands, thickets; flowering July to October.

Synonyms include Polygonum virginianum, Tovara virginiana, Antenoron virginianum, Tovara virginiana f. rubra, Tovara virginiana var. glaberrima

The deflexed pedicels are under strong tension and when disturbed can propel the fruit 3–4 m from the plant (hence the name Jumpseed). The persistent hooked styles aid in animal dispersal. The plants are easy to recognize when young by the relatively large, ovate leaves and often very prominent maroon chevron that disappears as the leaves age. Small flies, bees and wasps are observed visiting the flowers and Robber Flies use the plants to hunt prey. Herbivory by Sawflies in the genus Allantus creates holes in the leaves (https://www.inaturalist.org/observations/52429526).

Anecdotally, I have noticed that nearly every American Jumpseed has holes in the leaves, made by a native Sawfly. This Sawfly appears rarely to feed on the Asian Jumpseed. If the latter displaces the native species or corrupts it's genetic integrity, the viability of the Sawfly could be compromised along with its host plant. Let's just hope the technocrats in the invasive species industrial complex don't get the terrible idea to bring over an Asian Sawfly to "manage" this plant.

I recommend supporting the indigenous species and all its ecological benefits and removing the cultivar wherever found.

Except where explicitly stated, the words and research in this article are entirely my own. The facts belong to everyone. Please acknowledge that you heard it here first.

Suh, Y., S. Kim and C.W. Park. 1997. A phylogenetic study of Polygonum sect. Tovara (Polygonaceae) based on ITS sequences of nuclear ribosomal DNA. Journal of Plant Biology 40: 47–52.

Park, CW., M.G. Lee and H. Shin. 1992. A systematic study of Polygonum sect. Tovara (Polygonaceae): analysis of morphological variation. Korean Journal of Botany 35: 385–392.

Mun, J.H. and C.W. Park. 1995. Flavonoid chemistry of Polygonum sect. Tovara (Polygonaceae): a systematic survey. Plant Systematics and Evolution 196: 153–159.

Publicado el octubre 26, 2020 04:40 TARDE por danielatha danielatha | 11 comentarios | Deja un comentario

21 de octubre de 2020

The Cosmopolitan Quickweeds (Galinsoga) of the World

Quickweeds. Shaggy soldier, Galinsoga quadriradiata (L), Gallant Soldier, Galinsoga parviflora (R), Photo 528808, (c) Kyle Jones, some rights reserved (CC BY-NC). Shaggy Soldier, Galinsoga quadriradiata. Two disc flowers and fruit with acuminate pappus scales (L); one ray flower and fruit with pappus scales nearly as long as corolla tube (R).Photo 9072390, Daniel Atha, public domain.

Galinsoga (Quickweed) is a genus of 15–30 species indigenous to the Americas and centered in Mexico (Canne, 1977; Canne-Hilliker, 2006). Two species are cosmopolitan, occurring in disturbed places in most countries of the world: Galinsoga quadriradiata and Galinsoga parviflora. Currently, only these two species are known from the continental US (USDA NCRS, 2020). Judith Canne-Hilliker who studied these plants for decades published works on the taxonomy of the genus and her work is the basis for modern floras that treat the species. A few additional studies have been done as well. For example, Braden and Cialone found that achenes of Galinsoga quadriradiata are significantly shorter and wider than those of Galinsoga parviflora (Braden & Cialone, 1971). Based on the literature and what could be observed in the field it was clear that the two species were distinct, but I was frustrated by the challenges in separating them, especially from fresh material in the field and from photographs on iNaturalist. The study described here was my attempt to address this problem. See the observation here for images of seedling development.

Materials and Methods
I examined all the herbarium specimens of Galinsoga quadriradiata and Galinsoga parviflora from North America at the New York Botanical Garden (NY) and the Brooklyn Botanic Garden (BKL) (over 300 specimens). Using a compound microscope and strong light, I sorted all specimens by the characters used by Judith Canne-Hilliker and flora writers to separate the two species. I ignored identifications and used only the traits of: rays with well-developed pappus about equaling the tube vs. rays with vestigial pappus scales or scales absent; pappus scales of the disk flowers awn-tipped vs. blunt.

Here is a good view of the pappus scales of the disk flowers and the pappus of the ray flowers in Galinsoga quadriradiata. In Galinsoga parviflora the ray pappus is absent.

I ended up with three piles, one much larger than the other two. The smallest pile consisted of specimens for which it was not possible to determine nature of disc and ray pappus scales. I then examined the two larger piles for hair and leaf teeth character states.

All of the specimens (100%) that sorted by lack of ray pappus and blunt disc scales (the middle sized pile) were found to have very short (<0.5 mm), unicellular hairs (on stems and leaves) and narrow-ovate leaves with mostly entire or merely crenate margins. The larger pile with ray pappus scales present and acute or awn-tipped disc pappus scales were all found to have long (> 0.5 mm) multicellular hairs (on stems and leaves) and wider leaves with definite acute teeth. It was then possible to sort the smaller, undetermined pile on the basis of hair and leaf characters alone so that all specimens were identifiable as one or the other species.

Outside of Mexico, Galinsoga quadriradiata is the most common of the two species. On the continent of Europe, the species occurs at just over twice the rate of Galinsoga parviflora (2,296 to 988, as of 17 Nov 2020). But in the United States, the species occurs at over ten times the rate of Galinsoga parviflora (2,214 to 214). In Asia it is 537 to 120. On the continent of Australia there are thirty-six observations of Galinsoga parviflora and no Galinsoga quadriradiata--so far.

Key to the Cosmopolitan Quickweeds of the World

1a. Stems and leaves pubescent with multicellular hairs 0.5–1(-2) mm long; leaf margins dentate, the teeth obtuse to acute; limb of ray flowers 2–5 mm long, the pappus scales about as long as the tube; pappus scales of disk flowers sharp-acuminate, lacerate..... Galinsoga quadriradiata

1b. Stems and leaves glabrous to sparse pubescent with unicellular hairs 0–0.5 mm long; leaf margins crenate, the teeth rounded; limb of ray flowers 0–2 mm long, the pappus scales minute or absent; pappus scales of disk flowers truncate to obtuse, fimbriate..... Galinsoga parviflora

The results obtained here and those of previous work elucidate several traits that are discrete, objective and unambiguous. Further, these traits are consistently correlated with each other to form a distinct assemblage of character states that unambiguously and consistently define the species. Each couplet (1a and 1b) in the dichotomous key above is a series of characters (separated by semicolons). The two species share these characters (such as pubescence or leaf margins) but not the values or attributes of that character. The values of each character are called character states. The character states exhibited by a species (such as hairs longer than 0.5 mm or shorter than 0.5 mm) are discrete and unambiguous for the two species. They are true for one species or the other, but not both. Each couplet is thus a summary of the assembled traits (characters and values) that define that species and can be used as a brief description (often called a diagnosis in older literature).

The process undertaken in the present study can instruct others seeking to distinguish taxa based on simple terms understood by a general audience and what can be observed with the naked eye or a hand lens. In photographs and often even in the field, it is not possible to dissect the specimen to examine minute and often highly technical features. But monographs, floras and even field guides may rely solely on minute and difficult characters to distinguish species (as in Galinsoga). For nearly all photographs of Galinsoga in iNaturalist, these characters are impossible to see and thus only tentative identifications were possible prior to this study. Working with preserved specimens I could examine under a microscope, I used the technical characters in a process of reciprocal illumination to find other, more easily observable traits by which the species could be identified. Based on the simple traits described here and summarized in the dichotomous key above, it is now possible for anyone to confidently identify Galinsoga in the field and from photographs such as those on iNaturalist.

This procedure may fail to reveal easily observable traits to distinguish cryptic species in other genera, but I have used it with success in Smartweeds (Persicaria) and in genera of other families.

Outside their native range, the two weedy species, Galinsoga quadriradiata and Galinsoga parviflora are often found growing side by side in mixed populations. Care should be taken when taking multiple photos in a single population.

It may only be a matter of time before additional Galinsoga species are found in the continental United States, especially in areas adjacent to Mexico, center of diversity of the genus.

Canne-Hilliker, J. 2006. Galinsoga Ruiz and Pavón, Pp. 180–182. in Flora of North America Editorial Committee (eds.). Flora of North America North of Mexico, Vol. 21. Magnoliophyta: Asteridae, part 8: Asteraceae, part 3. Oxford Univ. Press, New York; Canne, J.M. 1977. A revision of the genus Galinsoga (Compositae: Heliantheae). Rhodora 79: 319–389; USDA NCRS. 2020. Galinsoga. United States Department of Agriculture, Natural Resources Conservation Service accessed 21 October 2020; Braden, D.A. and J.C. Cialone. 1971. Characterization of two Galinsoga R. & P. species from New Jersey by achene length/width ratio and the presence of marginal cotyledonary hairs. Bulletin of the Torrey Botanical Club 98: 50–52.


This post is dedicated to Judith Canne-Hilliker, student and master of Galinsoga, who passed away in Guelph, Canada on October 27, 2013.

Except where explicitly stated, the words and research in this article are entirely my own. The facts belong to everyone. Please acknowledge that you heard it here first.

Publicado el octubre 21, 2020 05:22 TARDE por danielatha danielatha | 14 comentarios | Deja un comentario

20 de octubre de 2020

The Case for Recognizing Persicaria amphibia and Persicaria coccinea as Distinct Species

Daniel Atha, revised February 6, 2024


This post is a preliminary summary of my findings and is written for the benefit of all interested in Smartweeds. The results of this research will be incorporated into a formal scientific publication. I am grateful for all of the observations that are helping clarify the taxonomy.

The issue is that the Water Smartweeds were long considered by most botanists to represent two or more distinct species with extremely variable morphologies depending on the habitat. The consensus abruptly shifted after 1968, when Richard Mitchell published his dissertation research (Mitchell, 1968) concluding that the presence of intermediates suggesting a continuum of variation proved that there was just one highly variable species called Persicaria amphibia.

The work presented here is not an in-depth analysis of Mitchell's findings. That will be presented later. What I wish to show is that based on the totality of evidence available today and sound taxonomic principles, the plants collectively known as Water Smartweeds are indeed at least two distinct species. Yes, there are plants that seem to be intermediate in one or more characters as Mitchell elegantly and conclusively demonstrated. But they are a small fraction of the total and their presence, however interpreted, is not proof of a single species.

I am inspired by the beauty and ecological importance of these plants and motivated by a desire to protect them from further degradation. That’s why I posted this extended explanation and why I include a link to the post along with my identifications. Thank you for taking the time to read it.

My interest in Persicaria began in 2008, when I found a Smartweed plant (Persicaria extremiorientalis) right outside my office door and all over New York City that had been in North America for fifty years, yet was unrecognized by all botanists, including Arthur Cronquist, one of the most famous and influential botanists of the twentieth century, who wrote the flora of the northeastern United States and who had an office in the same building (although not at the same time). Unfortunately he passed away in 1992, just months before I started my internship.

I've collected hundreds of Persicaria specimens and examined thousands more in major herbaria. I have studied the literature old and new, published papers, been a peer-reviewer for journals and corresponded with the handful of Polygonaceae specialists practicing today. I know the North American species pretty well and can recognize most from photographs. Ever so gradually, the plants are teaching me how to distinguish the species and since 2010, I've discovered three species new to North America (Persicaria hispida and Persicaria posumbu, in addition to Persicaria extremiorientalis).

The Water Smartweeds, Persicaria amphibia and Persicaria coccinea attracted my attention early on because they are such beautiful plants, yet no one seemed interested in them, perhaps because of their tortured taxonomic history. The more I learned about them and the sorry state of our professional conclusions, the more I wanted to “understand” them and reveal their unique qualities and relationships to each other and their surroundings.

Figure 1. Water Smartweed, Persicaria amphibia var. stipulacea (Photo 160158626, (c) Ian Guthrie, some rights reserved (CC BY-NC), uploaded by Ian Guthrie). Is it an exaggeration to say this is one of the most beautiful plants there is? The wonderful photo helps us see it.

Figure 2. Scarlet Smartweed aka Longroot Smartweed, Persicaria coccinea (Photo 298785464, (c) Ocean, some rights reserved (CC BY-NC), uploaded by Ocean). This is another spectacular photo that captures the essence of the plants with superb aesthetic qualities such as light, texture, color, form, movement, balance and composition.

Smartweeds are a genus of about 100 species primarily of the north temperate zone of both hemispheres. Most species are annuals with simple, alternate, entire, ovate or elliptic leaves and spicate inflorescences with small, five-parted flowers. Hybridization, introgression and polyploidy are especially common in the core “Eupersicaria” group of the genus. There are few autapomorphies (unique derived traits) that clearly distinguish one species from another. Often a suite of characters are necessary to define a species and distinguish it from others. In addition, the species can be quite variable and morphologically plastic in response to environmental conditions, especially periodic inundation (as are the two species discussed here). The Pale Smartweed Persicaria lapathifolia, Lady’s Thumb Persicaria maculosa and Persicaria densiflora can also form inflated, floating stems when flooded.

Persicaria amphibia var. stipulacea and Persicaria coccinea (Persicaria amphibia var. emersa) are perennial North American natives that inhabit high-quality, oligotrophic and mesotrophic wetlands, especially the OBL oligotrophic Persicaria amphibia var. stipulacea. They are both adapted to fluctuating water levels (hence the “amphibious” epithet). Persicaria amphibia (sensu stricto) is normally an aquatic with floating leaves, but when stranded on dry banks can grow aerial shoots (with often with flared ocreae). Persicaria coccinea is normally a palustrine species with aerial shoots, but can tolerate temporary flooding and may sometimes develop floating stems and leaves, but never flared ocreae.

The two species are treated as varieties in the current iNaturalist classification, strictly adhering to Plants of the World Online (POWO), which itself follows the influential opinion of Richard Mitchell (1968) who did his dissertation research on these plants. Recognition at the varietal level is far better than just one heterogeneous species (as Persicaria amphibia) advocated by Mitchell, but still short of the two species classification widely accepted before 1968 and suggested by the evidence presented here.

How we recognize these taxa is of critical conservation concern. Species of Persicaria are an important source of food for wildlife, especially waterfowl which share the same habitat and consume large quantities of the seeds. Persicaria amphibia and Persicaria coccinea often occur in extensive, dense populations and are primary producers, cycling nutrients and supplying food and habitat for macro- and micro- invertebrates as well as vertebrates (Partridge, 2001).

The vast majority of specimens and observations across North America will key out clearly with the key below. But there are populations that don’t, especially in the mountain west. These anomalies may be genetic mixtures from hybridization and introgression, both phenomena common and well-documented in the genus. Each species’ extreme anatomical plasticity and the existence of intermediate specimens has thrown botanists into taxonomic fits for 200+ years, lumping the entire range into one artificial super-species (e.g., R. Mitchell) or dividing every minor morphotype into a separate species (e.g., E.L. Greene).

Persicaria amphibia is a circum- boreal and -north temperate species occurring in America, Asia and Europe. It has long been recognized that the American plants are distinct at some level from the Eurasian as evidenced by the capacity to produce flared ocreae on aerial shoots when stranded. The Eurasian plants never do. Persicaria amphibia has over one hundred heterotypic synonyms just in North America! When recognized at the varietal level the correct name for the American plants is Persicaria amphibia (L.) Delarbre var. stipulacea (N. Coleman) H. Hara. At the subspecies level, the correct name is Persicaria amphibia subsp. laevimarginata (Hultén) Soják.

Persicaria coccinea, Scarlet Smartweed, is endemic to North America. It has almost as many synonyms. The correct name at the species level is Persicaria coccinea (Muhl. ex Willd.) Greene. As a variety of Persicaria amphibia the correct name is Persicaria amphibia var. emersa (Michx) J.C. Hickman.

Materials and Methods

Most taxonomic studies are conducted on a limited number of herbarium specimens, usually a handful and rarely numbering in the hundreds. Molecular studies today often use one sample per species. Herbarium specimens are very informative in ways photographs and illustrations will never be. They can be dissected, measured and their DNA analyzed. But ecological data is often poor or absent. The conclusions presented here are based on close examination of the nearly 10,000 observations of Water Smartweeds (Persicaria amphibia sensu lato) in iNaturalist, most of the extant herbarium specimens and observation in the field.

An often overlooked and rarely discussed issue with many taxonomic studies is the logical problem of sample selection, potentially leading to confirmation bias and circular reasoning. These can be avoided by random sampling. But that has its own set of biases and could exclude plants with the traits we wish to analyze.

This study is essentially a meta-random sample. All of the available specimens and observations are analyzed with the same criteria. The thousands of observations made by others across the entire range of the taxa are included. The iNaturalist observations were made by almost 6,000 observers for a range of purposes unrelated to this study. They are examined and analyzed by me randomly as they appear in the simple taxon search and none are excluded.

Each specimen and observation is assigned a name based a suite of morphological criteria traditionally used to distinguish the taxa. These include leaf shape (when floating and stranded); ocreae flared or not; and length and shape of inflorescence spike.

Key to the species of Water Smartweeds. (For an extended key see Reveal and Atha, 2012).

A. Plants palustrine, usually with emergent leafy stems; ocreae never with flared apices; leaves ovate or lanceolate (widest below the middle); inflorescence spikes usually 2 (unequal), cylindrical, usually > 4 cm long; flowers usually scarlet...… Persicaria coccinea (Persicaria amphibia var. emersa).

A. Plants aquatic, usually with floating stems and leaves; ocreae with flared apices (when stranded); leaves oblong or elliptic (widest at the middle); inflorescence spikes usually 1, ovoid, < 4 cm long; flowers usually pink...…Persicaria amphibia var. stipulacea.


The hypothesis that there are two distinct species (Persicaria amphibia and Persicaria coccinea) and possibly one or more hybrids is strongly supported by the data.

When applied to the nearly 10,000 observations of Water Smartweed (Persicaria amphibia s.l.), the character states in the key above prove to be highly consistent and predictive. Each of the characters are significantly correlated, so that if you find a palustrine plant with ovate or lanceolate, aerial leaves it will have long, cylindrical inflorescence spikes (99% of the time). On the other hand, if you find an aquatic plant with oblong, floating leaves it will have short, ovoid spikes (99% of the time). The flared ocreae is significantly correlated with oblong leaves and short spikes. Richard Mitchell's studies found the same results, but he emphasized the significance the few apparent intermediates.

Geography is only sometimes considered a significant taxonomic character, probably because resolution of habitat and geographic ranges have traditionally been poor due to very limited samples available in herbaria and the fact that plants do in fact move over time through dispersal and habitat alteration. iNaturalist is changing that in a big way. Now with thousands or sometimes tens of thousands of samples available we are getting closer to true and accurate range maps for many of the charismatic species (which includes these two). It is now apparent that correlation between geography and morphology is very strong and stark in these two species. More broadly, iNaturalist has now incorporated geography into its AI algorithms with significant improvement in predictive values. Richard Mitchell sampled only three populations from the vicinity of San Francisco.

Persicaria amphibia var stipulacea (plants with oblong leaves, short spikes and flared ocreae) is not found south of the Laurentide Ice Sheet (and see here) except in the mountain west and Mexico. See map of this species here. Note the observation near St. Louis, tracking precisely the southernmost extent of glaciation.

Persicaria coccinea (plants with ovate leaves, long spikes and no flared ocreae) is found nearly throughout North America except the extreme southeastern coastal plain and the far north. It has not been observed north of Edmonton, Canada, unlike Persicaria amphibia which extends through Alaska across the Bering Sea and into Asia. See map of this species in North America here.

The results suggest that Persicaria amphibia is somewhat rare in North America and that the species should probably be tracked by Natural Heritage programs throughout much of its range, especially along the southern boundary in New York, Pennsylvania, West Virginia, Kentucky, southern Ohio, Indiana, Illinois and Missouri. The true abundance at a local level is impossible to ascertain today because so many datasets do not distinguish the two taxa, even as varieties. But as the species are segregated in more data sets and floristic accounts it will become clearer how rare true Persicaria amphibia is today. Failure to recognize Persicaria amphibia as distinct from Persicaria coccinea could result in a cryptic decline in the former-- if it has not happened already. At the very least, the recognition of varieties is critical to conserve the gene-pools of both taxa. The most prudent course is to conserve all taxa wherever and whenever possible and that requires accurate identification of the taxa involved.

Results Summary

  1. Distinct morphologies. The vast majority of plants clearly exhibit a number of quantitative, discontinuous and correlated character states consistent with one species or the other.
  2. There are rare exceptions that appear to combine character states of the two species: See for example this observation. It has two, unequal elongate spikes like Persicaria coccinea, but has pale flowers, flared ocreae and oblong leaves like Persicaria amphibia. In this case, the plant overall is more like Persicaria amphibia, just with two, somewhat elongate spikes. And here is an example of a terrestrial plant with aerial shoots, large, ovate leaves and flared ocreae. But these leaves are glabrous, unlike the usually strigose palustrine form of Persicaria coccinea. These are two 1,000 that seem to combine character states of both species. Before we jump to the conclusion that these two plants and perhaps others like them "prove" they are one species, we have to eliminate all other possible explanations, like random mutation, hybridization, introgression, misinterpretation of the evidence or even one or more additional species.
  3. Distinct geographic ranges. This is becoming more and more clear as the observations accumulate. There are now almost 10,000 observations of the two species in North America and they clearly have different distributions. There are no plants with typical Persicaria coccinea character states in the far north. And there are no plants with typical Persicaria amphibia character states south of the Laurentide ice sheet in the eastern US. Very few plants better illustrate the correlation between past glaciation and present range than Persicaria amphibia.
  4. No single plant has ever been found to possess the traits of Persicaria coccinea at one end of the long rhizome and Persicaria amphibia at the other, even though there is ample opportunity for them to do so based on the position of the rhizome and level of inundation. For an example of this, see the observation here. I have seen most of the herbarium specimens of both species in North America and all the iNaturalist observations and I have never seen a plant with erect shoots and long inflorescences on the stem portion out of water and oblong floating leaves and short inflorescences on the stem portion in the water. But there are many examples of Persicaria amphibia with floating leaves at one end of the rhizome and erect shoots at the other.
  5. If they are one species with blended genetics, how can it be that no Persicaria coccinea like plant has ever been found with flared ocreae? That character is found exclusively in plants with the character states of Persicaria amphibia var. stipulacea.
  6. The most parsimonious explanation for plants with some intermediate character states is that the they are hybrids. To consider the entire range as one species based on these very rare specimens is the least good explanation. R.S. Mitchell did not consider this possibility (as the null hypothesis) when he lumped them for his PhD thesis in 1968.
  7. Taken all together these data are consistent with the consensus definition of a species in botany.
  8. If we reject morphological boundaries in Persicaria as currently defined based on the tiny fraction of apparent intermediates, we would lose half the species in Eupersicaria.


To consider the null hypothesis (for this study) and treat them as a single species (even with varieties or subspecies), as many did after 1968 (and some still do), requires ignoring the many morphological, genetic and geographic discontinuities between the taxa as proved by the evidence. These discontinuities are so distinct and so consistent, in most groups there would be no question they are two distinct species. The presence of a tiny fraction of individuals (ca. 0.01%) that appear to be intermediate in some characters does not prove they are a single species.

This looks like a classic case of convergence to me.

Lumping them together as a single species has very serious conservation implications. Conservation plans should conserve distinctive genetic lineages and conflating the two species could lead to the extinction of one or the other in the false belief that the "species" is preserved by the presence of at least some Persicaria amphibia s.l. We all know that most people tend not to use trinomials (myself included) and even heritage botanists and environmental surveyors will use the species name for convenience or uncertainty. U.S. Army Corps of Engineers data forms often omit subspecies or varieties, compromising the integrity and usefulness of EIS surveys that might include “Persicaria amphibia”


Thanks to iNaturalist, every observation used in this study is available to anyone with an internet connection. My materials and methods can easily be repeated exactly by anyone willing to spend the time. No complicated equipment, chemicals, algorithms, programs, institutional permission, journal subscription or specialized knowledge is required. That's what I love about natural history study and iNaturalist.


Atha, D. E. 2004. Polygonaceae. Pp. 308–310 in N. Smith, S. A. Mori, A. Henderson, D. Stevenson and S. Heald (eds), Flowering Plants of the Neotropics. Princeton University Press, Princeton.

Atha, D. E. & W. Carr. 2010. First Report of Persicaria hispida (Polygonaceae) from North America north of Mexico. J. Bot. Res. Inst. Texas 4: 561–564.

Atha, D. E., M. H. Nee & R. F. C. Naczi. 2010. Persicaria extremiorientalis (Polygonaceae) is established in the flora of the eastern United States of America. The Journal of the Torrey Botanical Society 137: 333–338.

Atha, D. and S. Rall. 2020. First report of Persicaria posumbu (Polygonaceae) for North America. Phytoneuron 2020-86: 1–7.

Burke, J. M. 2011. Revised subfamily classification for Polygonaceae, with tribal classification for Eriogonoideae. Brittonia. 63: 510–520.

Galasso, G., E. Banfi, F de Mattia, F. Grassi, S. Sgorbati & M. Labra. 2009. Molecular phylogeny of Polygonum L. s.l. (Polygonoideae, Polygonaceae), focusing on European taxa: preliminary results and systematic consideration based on rbcL platidial sequence data. Atti Soc. it. Sci. nat. Museo civ. Stor. Nat. Milano, 150(1): 113–148.

Kim, S. T. & M. J. Donoghue. 2008a. Incongruence between cpDNA and nrITS trees indicates extensive hybridization within Eupersicaria (Polygonaceae). American Journal of Botany. 95: 1122–1135.

Kim, S. T. & M. J. Donoghue. 2008b. Molecular phylogeny of Persicaria (Persicarieae, Polygonaceae). Systematic Botany. 33: 77–86.

Kim, S. T., S. E. Sultan & M. J. Donoghue. 2008b. Allopolyploid speciation in Persicaria (Polygonaceae): insights from a low-copy nuclear region. Proceedings of the National Academy of Sciences. 105: 12370–12375.

Massart, J. 1902. L'Accommodation individuelle chez Polygonum amphibium. Bull. Jard. Bot., Brux. [write out in full if that is the format required] 1(2): 73–95.

Mitchell, R. S. 1968. Variation in the Polygonum amphibium complex and its taxonomic significance. Univ. Calif. Pub. In Botany 45: 1–65.

Partridge, J. W. 2001. Persicaria amphibia (L.) Gray (Polygonum amphibium L), Biological Flora of the British Isles. Journal of Ecology 89: 487–501.

Reveal, J. L. & D. E. Atha. 2010. New combinations and typifications in Bistorta, Persicaria, Polygonum and Rumex (Polygonaceae). Brittonia 62: 243–263.

Reveal, J. L. & D. E. Atha. 2012. 8. Persicaria (L.) Mill. Smartweed, pp 236–250. in Cronquist et al. (eds), Intermountain Flora. The New York Botanical Garden Press, Bronx, NY.

Ronse Decraene L. P. & J. R. Akeroyd. 1988. Generic limits in Polygonum and related genera (Polygonaceae) on the basis of floral characters. Bot. Journ. Linn. Soc., London 98: 321–371.

Sanchez, A., T. M. Schuster, J. M. Burke & K. A. Kron. 2011. Taxonomy of Polygonoideae (Polygonaceae): a new tribal classification. Taxon. 60: 151–160.

Schuster, T. M., J. L. Reveal, K. A. Kron. 2011. Phylogeny of Polygoneae (Polygonaceae: Polygonoideae). Taxon. 60: 1653–1666.

Timson, J. 1965. A study of hybridization in Polygonum section Persicaria. Journal of the Linnean Society of London, Botany 59: 155–161.

Publicado el octubre 20, 2020 07:08 TARDE por danielatha danielatha | 24 comentarios | Deja un comentario