Every now and then we’ve had posts on this blog about non-anole lizards with anole-like dewlaps (e.g. 1, 2). Many agamids have flaps of skin under their throats that begin to resemble a dewlap, but male lizards in the South Asian genera Sitana and Otocryptis have the most “anoline” dewlaps I’ve seen so far. Indeed, some readers were almost fooled by Sitana’s resemblance, in both dewlap and dorsal patterning, to anoles. I spent the summer of 2012 documenting aspects of the display behaviour, morphology, and ecology of Sitana–here are some of my findings
Despite its ubiquity across much of peninsular India and Sri Lanka, Sitana remains relatively unstudied. Individuals across much of the range are classified as a single species, Sitana ponticeriana, despite substantial variation in dewlap morphology. It turns out that there are at least three dewlap variants, which occur, for the most part, in allopatry. Note the gradation in dewlap colouration between the three “morphs.”
Coloured-fanned, intermediate-fanned, and white-fanned male Sitana ponticeriana. Photographs by Shrikant Ranade, Jahnavi Pai, and Jitendra Katre respectively.
The objective of my fieldwork was to see whether the morphs differ in display behaviour, the logic being that if you have different tools with which to communicate, then you would communicate differently. The morph with the intermediately coloured dewlap does not breed in the summer (because of geographical variation in seasonal rainfall), so I only visited populations of the white-fanned and coloured-fanned morphs. Here are two videos, which show, I think, how differently the two morphs display.
There were no substantial differences in habitat occupied by the two morphs, possibly because I sampled primarily in disturbed habitats such as agricultural fields and grazing lands, where both morphs persist well. Their persistence in such habitats potentially obscures differences in habitat structure under which this dewlap variation evolved. However, it also demonstrates that the morphs are not limited to different habitats by their dewlap morphology. Sitana are highly terrestrial (average initial perch height across all lizards observed: 18 cm!), which must contribute to their persistence in these tree-less and shrub-less habitats.
A possibility I’m sure many of you are considering is that the intermediately-coloured morph pictured above is a hybrid of the other two. However, this does not appear to be the case. Both the white-fanned and coloured-fanned morphs occur in sympatry at one of the sites I sampled (near Kohlapur, Maharashtra), and we spotted nothing that looked remotely like a hybrid or like the intermediate-fanned morph at this site. I suspect that the three morphs are different species, and a phylogenetic study of this species complex is underway in Praveen Karanth’s lab at the Indian Institute of Science, so my suspicion can soon be confirmed or proven wrong.
Finally, there’s been some discussion of whether the coloured-fanned males develop their colours anew every breeding season. My field assistant, Chetan Kokatnur, attempted to resolve this debate once and for all by returning to one of our field sites after the breeding season was over. Unfortunately, there were no lizards to be found! We’ll keep looking, and report back when we solve the puzzle. I’m also excited to observe the display behaviour of the intermediately-coloured males in the near future, which ought to lend further insight into how this dramatic variation in dewlap colour in Sitana might have evolved (not surprisingly, I think sexual selection might be involved, but I’ll save that for a later post).
They’re highly terrestrial but two of the three pictures are on twigs. ?? Nature fakes!
Cool stuff Ambika. Besides having the dewlap and its associated behaviors in common with anoles, do they move and run like anoles?
Maybe nature fakes, but I’m guessing not. Males will perch on vegetation if it’s available, to display from higher perches. They also perch off the ground and on twigs in the heat of the day, a behaviour I don’t quite understand since I’m guessing it’s cooler under rocks and in crevasses. They aren’t very good at balancing on these twigs, however, and do better on rocks and the ground. Another difference that strikes me is their escape behaviour, which is to run as far as they can, and if possible, under rocks or into cracks in the ground. Given how camouflaged they can be against the ground, this works pretty well. In other respects, they move similarly to anoles.
Actually rocks can probably be almost as hot underneath as on top at midday – it depends on the thickness (Huey et al. 1989). Plus time spent under rocks or in crevices during the day is time lost for foraging, territorial defense, and reproduction (Sinervo et al. 2010). Bushes and other vegetation are probably a little cooler than rocks at midday, so a displaying lizard might want to switch to those perches if they want to remain active at the hottest times of the day.
Sorry if I wasn’t clear. They don’t remain active at the hottest times. They just remain perched on vegetation, often in full sunlight.
Holy moly! Have you taken their body temperatures at midday? Their dewlaps may be anoline, but their ability to tolerate what I can only imagine to be temperatures ~40C makes them very different indeed from anoles. Tough little buggers!
Forgot to mention that they also run bipedally pretty often.
Neat work, Ambika! If these morphs are independent lineages, I wonder how they’re partitioning niches to coexist at the sympatric site — any evidence there so far?
Thanks Brian, and great question–I have no idea! The coloured-fan morph is larger than than the white-fan morph (males a lot larger, females a little larger), which might have something to do with how they coexist. However, they are active at the same times of day, and are not isolated from each other at smaller spatial scales (i.e. you’ll find them on the same rock), so it’s not immediately obvious to me how the morphs partition niches. Definitely worthy of follow-up. However, that sympatric site is the only sympatric site known, and while I’m sure there are more such sites, they seem to be found more commonly in allopatry.
Ambika, if two or more of these morphs are sympatric, is it possible that you are seeing a phenomenon of the sort that Barry Sinervo documented with colour morphs and male mating strategies in Uta? You did mention sexual selection – have I jumped the gun here?
I don’t think so. First, they seem to be sympatric only rarely–the site I visited is, until now, the only known sympatric site. Second, they are morphologically distinct in other respects, and one can tell apart females of the white-fanned and coloured-fanned morphs (different patterning on the head and more subtle shape differences). Third, they didn’t seem to interact as though they were the same species–this sounds iffy, but we rarely saw inter-morph interactions, and definitely didn’t see males of different morphs displaying at each other, or males of one morph chasing females of the other morph, for example. However, we’re still very far from knowing what’s going on in this system!