Doubt about the taxonomic status of subspecies in both of the wild camelids of South America

@michaelweymann @michalsloviak @tonyrebelo @geichhorn @jwidness @jakob

There are two species of wild camelids in South America, namely the vicuna (Vicugna vicugna, https://www.inaturalist.org/taxa/42236-Vicugna-vicugna) and the guanaco (Lama guanicoe, https://www.inaturalist.org/taxa/42240-Lama-guanicoe).

In both,

  • there is sexual monomorphism, with so little difference in appearance between male and female that the sexes are hard to distinguish in the field,
  • the intraspecific variation is mainly latitudinal (north-south),
  • body size is considerably smaller in northern than in southern forms, and
  • the distributions are wide enough that subspecies have been postulated.

However, in both species, the question of subspeciation remains somewhat puzzling and unresolved.

In the case of the vicuna, there is no problem recognising the two subspecies, which look so different that raising them to the status of different species (Groves and Grubb 2011) seems reasonable.

What has not previously been pointed out is that the two subspecies differ categorically in a way.

The northern subspecies has conspicuous colouration overall, whereas the southern subspecies does not (https://www.inaturalist.org/journal/milewski/74636-adaptive-colouration-in-the-vicuna-camelidae-vicugna-vicugna#). Furthermore, confusion of identity, in which photos of the vicuna on the Web are mislabelled as the guanaco, occurs only in the case of V. v. vicugna.

However, the puzzle is how the two subspecies have remained distinct, despite the lack of a geographical barrier between them.

Vicugna vicugna vicugna and Vicugna vicugna mensalis live in similar landscapes, and under similarly extreme (high-altitude) climates. One merely replaces the other on a south-north basis - so abruptly that there seems to be no zone of natural intergradation.

In the case of the guanaco,

  • the northern and southern forms are as not as consistently different as in the case of the vicuna - despite the greater latitudinal span involved, and
  • there is more individual variation, within any given population, than in the case of the vicuna.

(What has not previously been pointed out is that the vicuna is one of the least individually variable of ungulates, all adult members within each subspecies appearing virtually identical once the effects of intermittent wool-shearing by humans are taken into account.)

In the guanaco the intraspecific variation seems too patchy and irregular to allow identification of subspecies on the basis of either appearance or region. A clinal, as opposed to subspecific, system of variation seems plausible.

The following is a closer scrutiny of subspecific variation in the two species.

VICUNA:

The northern subspecies of the vicuna, viz. Vicugna vicugna mensalis, is easily recognised by virtue of its frontal bleeze, centred on the chest:

https://www.shutterstock.com/it/image-photo/vicugna-one-duo-wild-south-american-1669487275
https://www.shutterstock.com/it/image-photo/andes-guanaco-pampa-chimborazo-ecuador-vicugna-1669487272
https://www.shutterstock.com/it/image-photo/walking-near-chimborazo-volcano-1897292002
https://www.shutterstock.com/it/image-photo/vicugna-one-two-wild-south-american-333453035
https://www.shutterstock.com/it/image-photo/portrait-wild-vicuna-arequipa-region-south-2131817439
https://www.shutterstock.com/it/image-photo/image-couple-guanacos-eating-grass-cajamarca-1902872560
https://www.shutterstock.com/it/image-photo/del-chimborazo-natural-fauna-national-park-2226795157
https://www.shutterstock.com/it/image-photo/llama-domesticated-south-american-camelid-widely-1018987360

The pale pelage in the southern subspecies of the vicuna, viz. Vicugna vicugna vicugna, emphasises the hips instead of the chest. However, it is not particularly conspicuous in either of these parts of the body:

https://www.shutterstock.com/it/image-photo/vicuna-vicgna-vicugna-high-altitude-camelid-22049122
https://www.shutterstock.com/it/image-photo/vicuna-vicgna-vicugna-high-altitude-camelid-22493302
https://www.shutterstock.com/it/image-photo/vicuna-vicgna-vicugna-high-altitude-camelid-22355119
https://www.shutterstock.com/it/image-photo/group-guanaco-lama-guanicoe-high-on-775035142 (mislabelled on the Web)
https://www.shutterstock.com/it/image-photo/guanaco-torres-del-paine-national-park-1478386475 (mislabelled on the Web)
https://www.shutterstock.com/it/image-photo/single-guanaco-somewhere-atacama-desert-chile-1332505547 (mislabelled on the Web)
https://www.shutterstock.com/it/image-photo/guanaco-torres-del-paine-national-park-1478386475 (mislabelled on the Web)
https://www.shutterstock.com/it/image-photo/guanacos-searching-food-atacama-desert-chile-1286391754 (mislabelled on the Web)
https://www.shutterstock.com/it/image-photo/guanaco-la-rioja-argentina-1718621131 (mislabelled on the Web)
https://www.shutterstock.com/it/image-photo/llamas-deserts-argentinian-1699860442 (mislabelled on the Web)
https://www.shutterstock.com/it/image-photo/guanaco-atacama-desert-chile-624501227 (mislabelled on the Web)
https://www.shutterstock.com/it/image-photo/lonely-guanaco-walking-on-rocks-chile-1562492434 (mislabelled on the Web)

GUANACO:

In the case of the guanaco:

Previous descriptions, in the literature, of the difference between northern and southern forms of the guanaco (http://www.isocard.net/images/journal/FILE486198178b052d8.pdf) seem inept/incomplete/misleading.

This because

  • it has been claimed that the northernmost subspecies, namely Lama guanicoe cacsilensis, tends to be relatively pale - which is not borne out by the many photos on the Web, from Peru and northern Chile,
  • a major point has been overlooked, viz. that the pale tracts on the posterior flanks and on the buttocks are poorly-developed, and
  • a minor point has been overlooked, viz. that the dark on the head extends relatively far to the posterior, including the ear pinnae in some individuals.

The following are the northernmost 44 observations of the guanaco in iNaturalist, west of the Andes, all of which would presumably fall within subspecies cacsilensis:

https://www.inaturalist.org/observations/141305341
https://www.inaturalist.org/observations/105181237 (apparently hybridised with Lama glama)
https://www.inaturalist.org/observations/7268729
https://www.inaturalist.org/observations/136755508
https://www.inaturalist.org/observations/40909643
https://www.inaturalist.org/observations/64786909
https://www.inaturalist.org/observations/8731923
https://www.inaturalist.org/observations/105856849
https://www.inaturalist.org/observations/40389324
https://www.inaturalist.org/observations/107268597
https://www.inaturalist.org/observations/70619726
https://www.inaturalist.org/observations/67199697
https://www.inaturalist.org/observations/107811089
https://www.inaturalist.org/observations/527136
https://www.inaturalist.org/observations/32921414
https://www.inaturalist.org/observations/91233424
https://www.inaturalist.org/observations/37350367
https://www.inaturalist.org/observations/142624917
https://www.inaturalist.org/observations/42546450
https://www.inaturalist.org/observations/75108809
https://www.inaturalist.org/observations/145560124
https://www.inaturalist.org/observations/106197145
https://www.inaturalist.org/observations/84919483
https://www.inaturalist.org/observations/93328362
https://www.inaturalist.org/observations/33554348
https://www.inaturalist.org/observations/32431037
https://www.inaturalist.org/observations/16793515
https://www.inaturalist.org/observations/36787442
https://www.inaturalist.org/observations/77991631
https://www.inaturalist.org/observations/77951617
https://www.inaturalist.org/observations/40967615
https://www.inaturalist.org/observations/126721594
https://www.inaturalist.org/observations/102013144
https://www.inaturalist.org/observations/19062955
https://www.inaturalist.org/observations/120576915
https://www.inaturalist.org/observations/37000683
https://www.inaturalist.org/observations/36390082
https://www.inaturalist.org/observations/120125601
https://www.inaturalist.org/observations/130006503
https://www.inaturalist.org/observations/27661333
https://www.inaturalist.org/observations/142179644
https://www.inaturalist.org/observations/7664369
https://www.inaturalist.org/observations/105877817
https://www.inaturalist.org/observations/146530144

What these photos reveal is a relatively uniform colouration, with a ground-colour that is not noticeably pale in most individuals. In these populations, most of the pale features of the species are relatively poorly-developed, disqualifying what I have referred to as

  • a lateral bleeze,
  • a frontal bleeze,
  • a posterior bleeze/flag, and
  • a laryngeal flag.

Furthermore, the head is consistently and extensively rather dark, the darkness extending to the ear pinnae in some individuals.

At the other (southern) extreme of the distribution of the guanaco lies the island of Tierra del Fuego (https://www.researchgate.net/publication/362053098_Guanaco_colonisation_of_Tierra_del_Fuego_Island_from_mainland_Patagonia_Walked_swam_or_by_canoe).

The many observations in iNaturalist from Tierra del Fuego can be seen in https://www.inaturalist.org/observations?nelat=-52.65826842464855&nelng=-63.79588773148024&place_id=any&swlat=-55.06352235315374&swlng=-68.6069750221495&taxon_id=42240. These all fall within the nominate subspecies, guanicoe.

Within these sets of photos, the clearest comparison is between
northern https://www.inaturalist.org/observations/27661333
southern https://www.inaturalist.org/observations/108379179

and

northern https://www.inaturalist.org/observations/106197145
southern https://www.inaturalist.org/observations/145216662

This confirms that the main difference between the northern and southern forms is the extension of the ventral pale pelage on to the flanks (constituting a lateral bleeze) in the latter.

Although this difference seems obvious, I have yet to see it pointed out in the literature. This omission may be partly because terms such as 'blaze', 'bles', and 'bleeze' are too specialised to be applied to general descriptions. However, by stating that it is the northern form that is the paler overall, previous authors have, in a sense, inverted the real relationship.

Although adapted to arid to semi-arid climates, the northern form of the guanaco is not pallid in the way so familiar in mammals and birds of deserts. It is, instead, better-described as relatively plain-coloured for its species.

Based on the consistent difference between northern and southern forms of the guanaco in the absence/presence of a lateral bleeze, I would have no objection to recognising these as valid subspecies, namely cacsilensis and nominate guanicoe. However, it remains possible that the variation is clinal (on a latitudinal basis), rather than subspecific.

Furthermore, it remains unclear how the remaining two postulated subspecies, namely voglii (Bolivia and northwestern Argentina) and huanacus (central Chile), relate to the colouration illustrated here.

It would make sense for voglii (east of the Andes) to differ from huanacus (west of the Andes), because they are separated by a formidable geographical barrier. However, clear differences among the three forms, cacsilensis, voglii (https://www.istockphoto.com/photo/guanacos-in-the-talampaya-canyon-gm1385221178-444115424?phrase=guanaco), and huanacus (https://www.inaturalist.org/observations/40923890), have yet to be demonstrated.

A strong case can be made - based partly on the lack of any cline/intergradation - for the recognition of Vicugna vicugna vicugna as a species separate from what is currently regarded as subspecies mensalis. It is, therefore, ironic that this relatively plain-coloured southern form of the vicuna is not only seldom appreciated for its distinctiveness, but it is frequently misidentified as the northern, relatively plain-coloured form of the guanaco.

This confusion, which is an embarrassment on the Web, results partly from the fact that both V. v. vicugna (high altitudes) and L. g. cacsilensis (low altitudes) occur in the Atacama region (in a sense broader than the low-altitude desert, https://en.wikipedia.org/wiki/Atacama_Region)

Publicado el febrero 18, 2023 08:11 MAÑANA por milewski milewski

Comentarios

NORTHERN FORM OF GUANACO (subspecies cacsilensis):

https://www.shutterstock.com/it/image-photo/guanaco-atacama-desert-chile-south-america-2256481085

https://www.shutterstock.com/it/image-photo/guanaco-atacama-desert-chile-south-america-2256480831

https://www.shutterstock.com/it/image-photo/guanaco-atacama-desert-chile-south-america-2256480833

https://www.shutterstock.com/it/image-photo/guanaco-atacama-desert-chile-south-america-2256480835

https://www.shutterstock.com/it/image-photo/guanaco-atacama-desert-chile-south-america-2256480991

https://www.shutterstock.com/it/image-photo/guanaco-atacama-desert-chile-south-america-2256481029

https://www.shutterstock.com/it/image-photo/guanaco-atacama-desert-chile-south-america-2256480845

https://www.shutterstock.com/it/image-photo/guanaco-atacama-desert-chile-south-america-2256480847

https://www.shutterstock.com/it/image-photo/guanaco-atacama-desert-chile-south-america-2256480853

https://www.shutterstock.com/it/image-photo/guanaco-atacama-desert-chile-south-america-2256480907

https://www.shutterstock.com/it/image-photo/guanaco-atacama-desert-chile-south-america-2256480855

https://www.shutterstock.com/it/image-photo/guanaco-atacama-desert-chile-south-america-2256480857

https://www.shutterstock.com/it/image-photo/guanaco-atacama-desert-chile-south-america-2256480877

https://www.shutterstock.com/it/image-photo/guanaco-atacama-desert-chile-south-america-2256480879

https://www.shutterstock.com/it/image-photo/guanaco-atacama-desert-chile-south-america-2256480901

https://www.shutterstock.com/it/image-photo/guanaco-atacama-desert-chile-south-america-2256480903

https://www.shutterstock.com/it/image-photo/guanaco-atacama-desert-chile-south-america-2256480905

https://www.shutterstock.com/it/image-photo/guanaco-atacama-desert-chile-south-america-2256480851

https://www.eso.org/public/images/potw1601a/

https://www.tripadvisor.com/LocationPhotoDirectLink-g303681-d1159798-i23173810-Nayara_Alto_Atacama-San_Pedro_de_Atacama_Antofagasta_Region.html

https://www.alamy.com/guanaco-in-atacama-desert-chile-south-america-image513972671.html

Publicado por milewski hace alrededor de 1 año
Publicado por milewski hace alrededor de 1 año
Publicado por milewski hace alrededor de 1 año
Publicado por milewski hace alrededor de 1 año
Publicado por milewski hace alrededor de 1 año

The following footage shows that, in the guanaco in Tierra del Fuego, the lateral bleeze occurs in most or all individuals:

https://www.youtube.com/watch?v=Ed1YLek0xhc

Publicado por milewski hace alrededor de 1 año
Publicado por milewski hace alrededor de 1 año

EVEN MORE PHOTOS OF VICUGNA VICUGNA VICUGNA, MISLABELLED AS GUANACO ON THE WEB:

https://www.istockphoto.com/photo/wild-vicu%C3%A3as-guanacos-and-llamas-grazing-on-the-hills-of-the-atacama-desert-chile-gm1385154372-444073978?phrase=guanaco

https://www.istockphoto.com/photo/guanaco-in-the-atacama-desert-gm1311138630-400328381?phrase=guanaco

https://www.istockphoto.com/photo/group-of-guanacos-in-atacama-desert-gm1144549440-307751318?phrase=guanaco

https://www.istockphoto.com/photo/guanaco-gm1290018660-385520940?phrase=guanaco

https://www.istockphoto.com/photo/guanaco-vicuna-in-the-wild-of-atacama-desert-andes-altiplano-chile-gm1415856714-464064070?phrase=guanaco

https://www.istockphoto.com/photo/guanaco-vicuna-in-the-wild-of-atacama-desert-andes-altiplano-chile-gm1415856914-464064328?phrase=guanaco

https://www.istockphoto.com/photo/two-guanaco-vicuna-in-the-wild-of-atacama-desert-andes-altiplano-chile-gm1415856975-464064389?phrase=guanaco

https://www.istockphoto.com/photo/group-of-guanacos-in-atacama-desert-gm1144561711-307751351?phrase=guanaco

https://www.istockphoto.com/photo/guanaco-at-volcanic-landscape-of-atacama-desert-gm1142841917-306692800?phrase=guanaco

https://www.istockphoto.com/photo/guanaco-at-volcanic-landscape-of-atacama-desert-gm1142843086-306692826?phrase=guanaco

https://www.istockphoto.com/photo/vicuna-guanaco-animal-wildlife-in-bolivian-andes-altiplano-and-idyllic-atacama-desert-gm848380618-139399565?phrase=guanaco

https://www.istockphoto.com/photo/vicuna-guanaco-animal-wildlife-in-andes-altiplano-and-idyllic-atacama-desert-volcanic-gm847054216-139017235?phrase=guanaco

https://www.istockphoto.com/photo/vicuna-guanaco-group-of-animals-animal-wildlife-in-andes-altiplano-and-idyllic-gm836599284-136210171?phrase=guanaco

Publicado por milewski hace alrededor de 1 año
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