Jackal genus Lupulella evolved flank-banding not once, but twice

Also see https://www.inaturalist.org/journal/milewski/55016-why-lupulella-adusta-could-be-called-the-baffledog#.
 
The genus Lupulella (https://www.inaturalist.org/observations?place_id=any&taxon_id=1210963&view=species) contains just two spp., namely mesomelas and adustus.

These two spp. have similar body masses, and both are restricted to subSaharan Africa.

Furthermore, they are partly sympatric, both north and south of the equator.

Both retain generalised diets, including scavenged carcases, with mesomelas more adapted for carnivory, and adustus more adapted for frugivory.

The species of Lupulella remain ‘jackals’, ecologically comparable with Eurasian Canis aureus (https://www.inaturalist.org/taxa/851014-Canis-aureus).

However, they have segregated ecologically, with

• mesomelas tending to be bold, diurnal, predaceous, and drought-resistant, vs
• adustus instead tending to be shy, nocturnal, able to resort to plants for food, and water-dependent.

Accordingly, mesomelas tends to live in thorn scrub and grassland, whereas adusta tends to live in woodland and marshes, and at the edge of forests.
 
The aim of this Post is to test one aspect of the similarity of the two spp. of Lupulella.

Both spp. have flank-banding, and no other form of jackal worldwide possesses such a pattern.

Therefore, the question arises of whether flank-banding is phylogenetically ‘deep’ in this African lineage, or whether on the other hand it has evolved independently in the two species, for different adaptive reasons.

Another way of posing the same question is to ask whether the flank-banding of the two spp. of Lupulella is homologous or analogous.

If it is homologous, this implies that flank-banding evolved once in Lupulella, was present in the common ancestor of the two extant spp., and has merely been modified differently in mesomelas vs adusta.

If it is analogous, that implies that the ancestor did not necessarily possess flank-banding, but this pattern arose, in different form and for different adaptive reasons, in the two species.
 
My analysis of photos has led me to a clear answer: flank-banding is phylogenetically a relatively ‘shallow’ feature of Lupulella, and the two spp. show analogy rather than homology in possessing it.
  
The following (https://www.natureinstock.com/search/preview/side-striped-jackal-canis-adustus-stretching-and-licking-its-lips-after/0_00003537.html and https://image.jimcdn.com/app/cms/image/transf/dimension=1920x400:format=jpg/path/s42980ac6afc5c05d/image/idd655fdf182e261a/version/1486457893/image.jpg) show how similar the flank-banding can be in the two spp. of Lupulella.

In both cases we cross, from dorsal to ventral, the following bands:

• First, on the back, there is pelage of medium tone.
• Then there is a whitish band, which in both species is arranged at an angle to the horizontal and runs approximately from mid-scapula to the ileal hip-bone.
• Then, ventral to this, there is a narrow band of somewhat darker tone.
• Finally, the flanks are a relatively pale shade of medium-tone, i.e. paler than the back, but constituting a ‘ground-colour’ rather than a marking.

If all individuals conformed to these photos, we could safely conclude that

• the flank-striping in Lupulella is homologous, and
• ancestral Lupulella possessed similar banding, with merely the subtleties modified in the divergence between the two spp.

However, this is not the case, as we shall see below; the similarity in this first photo-pair is, if not illusory, then at least misleading.
 
The following photo-pair (http://www.wildlife-pictures-online.com/image-files/black-back-jackal_rc-6411g.jpg and https://www.flickr.com/photos/sriall/16062186992), this time with mesomelas first, allows us to home in on the first basic difference between the two spp.

This is that the most prominent element of the flank-banding in mesomelas is the darkest band, whereas the most prominent element of the flank-banding in adusta is the palest band. (Also see https://www.flickr.com/photos/leendert3/13967186872.)

In these two specimens, the two bands mentioned still occur at equivalent positions on the uppermost flanks. So, it remains possible that the banding is homologous, and that all that has happened in the divergent evolution between the two spp. of Lupulella is that the main band of adusta is a ‘negative’ (pale) of that of mesomelas (dark).

However, as we shall see below, even this qualified homology does not stand up to scrutiny.
 
The following (https://www.robertharding.com/preview/1116-49328/blackbacked-jackal-canis-mesomelas-stands-sunshine-watching-camera/ and http://fascinatingafrica.com/wp-content/uploads/2014/10/shutterstock_53768293-four-oaks.jpg) show the location of the main flank-band in mesomelas, which is relatively consistent among individuals.

It lies at a certain position on the region straddling the upper flanks and the back and rump, with a consistent angle to the horizontal. In mesomelas, individual variation in the configuration of the flank-banding is so limited that it takes a trained eye to spot them.

The two subspecies of mesomelas, namely schmidti and the nominate, hardly differ in this respect.
 
Now let us compare this with the location of the flank-banding in adusta.

This species is far more variable individually in the expression of flank-banding. This includes the degree of dark/pale contrast, as well as where exactly this contrast is located, relative to flank, back, and rump. Two photos should suffice to dispel any notion that adusta is just a ‘negative’ version of mesomelas.
 
In the first of my two examples, we see an individual in which the pale flank-band of the body is ‘broken’ from that on the rump/upper haunch, indicating that this animal possesses not one band, but two.

No individual of mesomelas ever shows dark/pale contrast on its rump/haunch in this position. Therefore, the two spp. are qualitatively, rather than quantitatively, different in this respect.
 
In the second of my two examples, we see an individual in which the pale flank-band of the body is continuous with that of the upper haunch, but not in the straight projection always seen in mesomelas.

Instead, there is a kink in the banding, because what has happened is that the diagonal dark band so common in jackals (shared with e.g. Canis aureus and Canis anthus) is actually the feature to which dark/pale contrast has been added.

It is obvious that there is no homology between adusta and mesomelas in the banding on the hindquarters. Examination of many photos bears out the same point in the case of the torso, as well.

Any resemblance between the two spp. in the location and pattern of the banding, such as we saw in the first photo-pair above, is misleading. Owing to the great individual variation in both spp., but particularly adusta, we can sometimes find a fortuitous similarity.

The conclusion: Lupulella seems to be a valid genus. However, in defining this clade, one cannot cite flank-banding as one of its ‘deeper’ phylogenetic features.
 
http://www.greatplainsconservation.com/bushbuzz/wp-content/uploads/2012/09/0133.jpg

(Also see a detailed comment below.)

Photo-summary of full range of individual variation within Lupulella adusta:
  
Any taxonomist or writer of field guide-books, trying to describe the species in terms of its ‘average’ or ‘normal’ colouration, will miss the point without pointing out that the most important thing about this appearance is that it is bewilderingly variable (and that this, by implication, is adaptive).
 
Individuality is obviously paramount in L.. adusta. I also have the impression that age is important, adolescents differing from fully mature adults in ways which have yet to be established. However, I have no evidence so far that sex is important, i.e. I have ignored the possibility of sexual dimorphism in colouration in L. adusta.
 
I get the impression that L. adusta is individually variable even in body-proportions. Some individuals look fairly ‘normal’ for a jackal, whereas others remind me, in their lankiness, of the South America Chrysocyon. I’m still not clear to what extent this variation in legginess and small-headedness, as well as long-tailedness, is ontogenetic. But even if it is mainly ontogenetic, it is still far greater than that seen in other spp. of jackals.
 
Another obvious question is: does the side-striping develop only in adulthood? My impression is that it does, and if so I don’t think this is far too important to remain unstated in published descriptions.
 
In order to summarise the full range of this variation in various aspects of the colouration, I have chosen the photos below.
 
Two important caveats. Firstly, there may well be subspecific variation in this widespread species, but for the purposes of this exercise I’ve ignored subspeciation and just assumed that L. adusta Africa-wide is a single population genetically, the phenotype of which it is that we find so unpredictable according to individual and perhaps age. Secondly, I have ignored the possibility that L. adusta is colour-polymorphic, instead just assuming that it is monomorphic but with extreme variation of a continuous, not correlated, kind. In other words, where a colour-polymorphic species such as the dingo would have a few discrete ‘colour-patterns’ in each litter, which remain regardless of how the colour-morphs are combined in matings, what I assume we have in L. adusta is a case of each individual having its own unique pattern. In other words, whereas colouration in a colour-polymorphic species is ‘sorted’ phenotypically without genotypic sorting, that of L. adusta seems to be ‘assorted’: each individual presents its own combination of features in what seems to be a ‘random scramble’.
  
TAIL LENGTH:
 
http://www.biodiversityexplorer.org/mammals/carnivora/images/sidestripedjackal3_327w.jpg
 
TAIL COLOURATION:
 
http://www.ultimatefieldguide.com/Mammals/777px-Side-striped_Jackal.jpg
 
http://farm8.static.flickr.com/7637/16951999937_38e64118a1.jpg
 
https://www.mindenpictures.com/cache/pcache2/90135625.jpg 
 
http://www.mammalogy.org/uploads/imagecache/library_image/library/2174.jpg
 
FACIAL MARKINGS:
 
http://www.serengeti.org/gfx/a_jackal_z.jpg
 
https://retrieverman.files.wordpress.com/2011/02/gray-side-striped-jackal.jpg
 
FLANK-BANDING:

https://upload.wikimedia.org/wikipedia/commons/thumb/4/46/Canis_adustus_Kidepo_National_Park.jpg/220px-Canis_adustus_Kidepo_National_Park.jpg 

https://s-media-cache-ak0.pinimg.com/736x/39/ac/26/39ac26e2fced81b93a453ed389997726.jpg
 
http://www.wackywildlifewonders.com/images/stories/africanwildanimals/jackal_side_striped_(c)toursa.jpg

HAUNCH-BANDING:
 
https://c1.staticflickr.com/4/3832/11819353505_ac3204b65b_b.jpg
 
http://photographersdirect.com/pdwm.php?i=1547497&s=12366&p=8
 
http://www.hotelbiriwabeach.de/Fast/GB/02_Ghana_Info_GB/04_Tiere_GB/03_Raubtiere_GB/Pic/Side_Striped_Jackal.jpg
 
http://blog.londolozi.com/wp-content/uploads/2011/11/Side-striped-jackal.jpg
 
https://goondwandotcom.files.wordpress.com/2014/02/the-side-striped-jackal-canis-adustus-is-a-nocturnal-dog-like-carnivore.jpg
 
MARKINGS ON CHEST & FRONT-OF-NECK:
 
http://l450v.alamy.com/450v/b7nx9w/africa-kenya-masai-mara-narok-district-a-side-striped-jackal-in-the-b7nx9w.jpg
 
http://i1229.photobucket.com/albums/ee470/VGueli/017a.jpg
 
HEAD SIZE & LEG LENGTH:
 
https://dewetswild.files.wordpress.com/2012/10/27-side-striped-jackal-shingwedzi.jpg?w=625
 
http://rpguide.soulsrpg.com/public/images/subspecies/jackal/ca_adustus2.png

Publicado el septiembre 5, 2022 10:18 TARDE por milewski