Rock-dwelling agamids on two continents: Ctenophorus vs Agama, part 3: variation in masculine colouration

...continued from https://www.inaturalist.org/journal/milewski/86326-rock-dwelling-agamids-on-two-continents-ctenophorus-vs-agama-part-2-#

ACKNOWLEDGMENT: I thank Johannes van Rooyen (@johannesvanrooyen ) for educating me about the differences between males and females, in Agama (https://www.inaturalist.org/observations/139408521). The patterns he has pointed out are, in hindsight, now evident to me. However, I was formerly oblivious to them, and field guide-books do not do justice to them, either.

Rock-dwelling agamids in Australia and southern Africa vary extremely in their degree of sexual dimorphism in colouration.

In this respect, they show no evolutionary convergence.

The variation goes along four lines, viz.

  • mature males vary from dull through bright-hued to gaudy, according to the species,
  • females (irrespective of breeding condition) are somewhat bright-hued in Agama planiceps, vs dull in all other spp.,
  • females have bright-hues associated with breeding condition in several spp. of Agama, but no other spp., and
  • mature males of Ctenophorus ornatus, which lack bright hues, differ from females only in the boldness of dark/pale contrast (banding on the tail, plus vertebral stripe).

Further details include the following.

Among mature males, the dullest is Ctenophorus rufescens, whereas the gaudiest are Agama kirkii and A. planiceps. This corresponds, approximately, to a difference between non-gregarious and gregarious, with corresponding polygyny.

Agama anchietae is odd in that it alone

  • among all the spp. studied, has colouration more conspicuous (at least to the human eye) in females than in males, and
  • among the southern African spp., has masculine colouration less conspicuous than that of Australian species (particularly Ctenophorus vadnappa).

This possibly corresponds to A. anchietae being less gregarious than its rock-dwelling congeners in southern Africa, in this way partly resembling the Australian spp. However, the bright hues in females of A. anchietae, in breeding condition, undermine this explanation.

A categorical difference emerging from this study is that females feature conspicuous hues (to the human eye) in no Australian species but all southern African spp. Given that females are the biologically central sex, this degree of intercontinental divergence is surprising indeed.

CTENOPHORUS DECRESII
https://reptile-database.reptarium.cz/species?genus=Ctenophorus&species=decresii&search_param=%28%28taxon%3D%27agamidae%27%29%29
https://upload.wikimedia.org/wikipedia/commons/9/93/Tawny_Dragon_%28Ctenophorus_decresii%29_%289388501921%29.jpg
https://www.inaturalist.org/observations/70549036
https://www.alamy.com/tawny-crevice-dragon-image233161693.html?imageid=3F80509B-E874-4192-B2E9-D4E7302AF092&p=464898&pn=1&searchId=30867f7d917ca1c646c057d35363de81&searchtype=0
https://www.alamy.com/tawny-dragon-ctenophorus-decresii-kangaroo-island-south-australia-image68465214.html?imageid=5B470933-8254-4B8C-8453-956BA5530690&p=3151&pn=1&searchId=30867f7d917ca1c646c057d35363de81&searchtype=0
https://www.alamy.com/tawny-dragon-ctenophorus-decresii-kangaroo-island-south-australia-image68465207.html?imageid=A8A5A01F-7C14-4461-AB02-1377D1BE2303&p=3151&pn=1&searchId=30867f7d917ca1c646c057d35363de81&searchtype=0
https://www.inaturalist.org/observations/36611400
https://www.inaturalist.org/observations/138814803
https://www.inaturalist.org/observations/42284755
https://www.inaturalist.org/observations/72999384
https://www.alamy.com/stock-photo-an-adult-male-tawny-dragon-ctenophorus-decresii-basking-on-a-boulder-127710572.html?imageid=C7EE46E9-EAA7-4704-90AA-3BCDD57E1D5C&p=70467&pn=1&searchId=30867f7d917ca1c646c057d35363de81&searchtype=0

CTENOPHORUS FIONNI
https://www.flickr.com/photos/126237772@N07/38823037014
https://www.inaturalist.org/observations/189078048
https://www.inaturalist.org/observations/151909788

CTENOPHORUS MIRRITYANA
https://media.australian.museum/media/Uploads/Journals/29833/1600_complete.pdf
https://www.inaturalist.org/observations/183446776
https://www.inaturalist.org/observations/183446767
https://www.inaturalist.org/observations/57321972

CTENOPHORUS MODESTUS
http://www.wildherps.com/species/C.decresii.html
https://www.alamy.com/stock-photo-an-adult-male-tawny-dragon-ctenophorus-decresii-basking-on-a-boulder-127710293.html?imageid=1A4D26E9-60E3-4358-AB67-11063BD7FB3A&p=70467&pn=1&searchId=30867f7d917ca1c646c057d35363de81&searchtype=0
https://www.inaturalist.org/observations/183608925
https://www.inaturalist.org/observations/159109651
https://www.inaturalist.org/observations/2385833

CTENOPHORUS ORNATUS
https://www.gettyimages.co.uk/detail/news-photo/ornate-crevice-dragon-ctenophorus-ornatus-geraldton-region-news-photo/578259988?adppopup=true
https://www.researchgate.net/figure/The-Ornate-dragon-lizard-Ctenophorus-formerly-Amphibolurus-ornatus-which-has-been-the_fig16_6488816
https://www.inaturalist.org/observations/174823301

CTENOPHORUS RUFESCENS
https://www.inaturalist.org/observations/145710007

CTENOPHORUS SLATERI
https://www.inaturalist.org/observations/147926463
http://reptilesofaustralia.com/lizards/agamids/Ctenophorus_slateri.html
http://www.wildherps.com/species/C.slateri.html

CTENOPHORUS VADNAPPA
http://www.wildherps.com/species/C.vadnappa.html
https://www.australianreptileguide.com/red_barred_dragon
https://inaturalist.ala.org.au/photos/2661278
https://www.flickr.com/photos/stephenmahony/52088081318
https://www.flickr.com/photos/whawha88/15686564651
scroll to third photo in http://www.sareptiles.co.za/forum/viewtopic.php?f=47&t=353
https://www.dreamstime.com/red-barred-dragon-red-barred-dragon-basking-rock-image189165138

AGAMA ANCHIETAE
https://www.inaturalist.org/observations/11226286
https://www.inaturalist.org/observations/187810182
https://www.inaturalist.org/observations/20847159

AGAMA ATRA
Fairly typical:
https://www.inaturalist.org/observations/140555242
https://www.inaturalist.org/observations/185312592
https://www.inaturalist.org/observations/33013148
https://www.inaturalist.org/observations/126337602

Extensive blue/turquoise:
https://www.inaturalist.org/observations/184891185
https://www.inaturalist.org/observations/173464316
https://www.inaturalist.org/observations/151739922
https://www.inaturalist.org/observations/143201236
https://www.inaturalist.org/observations/140659375
https://www.inaturalist.org/observations/126337602
https://www.inaturalist.org/observations/134165634
https://www.inaturalist.org/observations/31613657
https://www.inaturalist.org/observations/52145437
https://www.inaturalist.org/observations/9073971
https://www.inaturalist.org/observations/11278687
https://www.inaturalist.org/observations/11080747
https://www.inaturalist.org/observations/11090900

With prominent pale vertebral stripe:
https://www.inaturalist.org/observations/185255601
https://www.inaturalist.org/observations/183891676
https://www.inaturalist.org/observations/183861014
https://www.inaturalist.org/observations/179174034
https://www.inaturalist.org/observations/179396975
https://www.inaturalist.org/observations/18901898
https://www.inaturalist.org/observations/11076639
https://www.inaturalist.org/observations/102155724

With yellowish tail and maroon abdomen:
https://www.inaturalist.org/observations/139408587
https://www.inaturalist.org/observations/18814684
https://www.inaturalist.org/observations/59114885

AGAMA KIRKII
https://www.inaturalist.org/observations/61563187
https://www.inaturalist.org/observations/104277623
https://www.inaturalist.org/observations/152748306
https://www.inaturalist.org/observations/143995440
https://www.inaturalist.org/observations/143506272
https://www.inaturalist.org/observations/139008832
https://www.inaturalist.org/observations/135407748
https://www.inaturalist.org/observations/40679404
https://www.inaturalist.org/observations/39309769
https://www.inaturalist.org/observations/37259797
https://www.inaturalist.org/observations/35911714
https://www.inaturalist.org/observations/22471976
https://www.inaturalist.org/observations/18824986
https://www.inaturalist.org/observations/18773618
https://www.inaturalist.org/observations/8492368

AGAMA PLANICEPS
https://www.dreamstime.com/namib-rock-agama-planiceps-beautiful-orange-headed-lizard-southern-africa-rocks-mountains-namibia-image142778700
https://www.dreamstime.com/orange-blue-colored-lizard-namibian-rock-agama-agama-planiceps-male-posing-yellow-granite-rock-typical-desert-orange-image186525318
https://www.inaturalist.org/observations/11059682
https://www.inaturalist.org/observations/93374161
https://www.projectnoah.org/spottings/631096002/fullscreen
https://www.dreamstime.com/orange-blue-colored-lizard-namibian-rock-agama-agama-planiceps-male-posing-yellow-granite-rock-typical-desert-orange-image159583401
https://www.inaturalist.org/observations/31283144.

Posted on November 05, 2023 11:02 AM by milewski milewski

Comments

@ptexis @johannesvanrooyen @alexander @m_burger @botswanabugs @karoopixie

The following (https://www.inaturalist.org/observations/143788547) nicely illustrate the ambivalence of conspicuous colouration in Agama atra.

The individual shown is adult female, in breeding condition. The hues of feminine advertisement (apart from possible ultraviolet) are blue (slightly iridescent) and yellow, the former shared with mature males but the latter restricted to females.

It makes sense that males should be less risk-averse in their trade-offs between social/sexual advantage and avoidance of predation.

But the point of particular interest is the fine line maintained between social/sexual advertisement on one hand, and anti-predator camouflage on the other. Some concealment is maintained by a combination of a) the bright-hued lichens on the rocks, and b) the limited chroma (https://www.dictionary.com/browse/chroma) of the hues on the lizard.

This, I suggest, achieves 'the best of both worlds'.

Other relevant photos are https://www.inaturalist.org/observations/67462931 and https://www.inaturalist.org/observations/37948099. In these cases, the most conspicuous hue on the torso is orange, rather than yellow.

Incidently, the following (https://www.inaturalist.org/observations/143786388) show a mature male individual of the same species.

The colouration still shows some balancing of advertisement and concealment. However, the figure is, overall, unambivalently conspicuous. This is because of a) the rocky surface chosen, b) the pale vertebral stripe, which is incongruous with the background, and c) the retention of disruptive mottling only on the hindquarters (particularly the tail).

Posted by milewski 6 months ago

@milewski one must also remember that agamas can subdue their bright colours within a minute or two. So if they really feel threatened by a potential predator they can take that course of action. The following observations shows this colour change:
https://www.inaturalist.org/observations/190478860
https://www.inaturalist.org/observations/62039955

Posted by johannesvanrooyen 6 months ago

@johannesvanrooyen

Many thanks for this valuable comment.

Posted by milewski 6 months ago

The following, of Agama atra, show the subtle distinctions between females and males, when in breeding condition but with the hues 'switched off' in apprehension of the observer.

In females, any yellow that remains is located on the abdomen, just anterior to the hindleg: https://www.inaturalist.org/observations/88765446.

In males, the only yellow (restricted to certain individuals) is located on the ventral surface of the tail, and the abdomen just anterior to the hindleg is reddish, never yellowish: https://www.inaturalist.org/observations/58485269.

The following (https://www.inaturalist.org/observations/59114885) shows an individual male - which happens to feature yellow on its tail - with the hues 'switched on'.

@johannesvanrooyen Is this correct?

The following (https://www.inaturalist.org/observations/10954776) further illustrates the sexual differences.

Posted by milewski 6 months ago

@johannesvanrooyen

Which of the following statements is most correct, w.r.t. patterns of colouration (particularly in breeding condition) in Agama atra?

The species
a) consists of subspecies with different colouration,
b) is colour-polymorphic (https://www.cell.com/current-biology/pdf/S0960-9822(16)30193-2.pdf),
c) is neither subspeciated (w.r.t. bright hues) nor polymorphic, but shows individual variation,
d) shows a predictable sequence of colouration with age (within each sex), after becoming adult.

Posted by milewski 6 months ago

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