Periodically, we’ve discussed how green and brown anoles interact now that they’ve been thrown into sympatry in the southeastern U.S. and elsewhere–do they fight, do they mate, do they just ignore each other? Perhaps, it seems, a little bit of each. In any case, the latest report comes from Janson Jones over at Dust tracks on the web, who presents a nice tryptich of observations and photos on a one-side green-brown interaction in southern Georgia. As always, the photos are sumptuous and the text entertaining.
Author: Jonathan Losos Page 75 of 130
Professor of Biology and Director of the Living Earth Collaborative at Washington University in Saint Louis. I've spent my entire professional career studying anoles and have discovered that the more I learn about anoles, the more I realize I don't know.
Brown anole being eaten by a Cuban Treefrog. Photo by jwood10016.
Surely you remember the heart-warming story–the best post AA has ever had–about Gordon, the green anole that was almost eaten by a Cuban tree frog, but somehow escaped and lived to see many more days (if you haven’t, check it out now!). Well, apparently the story doesn’t always end so happily for anole-kind. Above is a photo from Orlando, Fl, of a brown anole going down the hatch, and there’s no reason to believe that it came back up. There’s a whole series of photos on planetisuzoo.
Earlier this spring, I reported on a trip to Colombia and Venezuela to collect natural history data on several unknown anoles: A. heterodermus, A. onca, A. annectens and A. tigrinus. As part of the Scientist at Work: Notes from the Field blog on the Science webpage of the New York Times, I wrote a series of posts, which have now all been published. If you’re interested, links to them are provided below.
Losos, J.B. March 12, 2013. Quest for a little-known suburban lizard. link to article
Losos, J.B. March 14, 2013. Life of a Lizard Wrangler. link to article
Losos, J.B. March 19, 2013. Lizard Olympics. link to article
Losos, J.B. April 2, 2013. A Beach Vacation, Lizard Style. link to article
Losos, J.B. April 11, 2013. An Embarrassment of Anoles. link to article
Losos, J.B. April 25, 2013. A Night of Saurian Spotlighting. link to article
The doyenne of Brazilian herpetology, Paulo Vanzolini died two days ago at an age of 89. Renowned for his herpetological expertise, Vanzolini was even more famous for his samba compositions. Indeed, his Wikipedia page focuses more on his music career and discography than his zoological contributions, an oversight that perhaps Wikipedia-savvy AA readers can rectify.
With regard to anoles, Vanzolini made two important contributions in collaboration with Ernest Williams. The first was their monographic treatment of variation in the mostly-Amazonian Anolis chrysolepis species complex, a group that was recently revised by D’Angiolella et al. This monograph was notable not only for its detailed study of geographic variation, but also for its suggestion that speciation may be prompted by climatic cycles that lead to contraction of populations into isolated, allopatric pockets of suitable habitat. This hypothesis was suggested simultaneously and independently of the same suggestion for Amazonian birds by Haffer and led to the influential and much-debated Pleistocene Refugia hypothesis, discussed previously in AA‘s pages.
Vanzolini and Williams had a follow-up paper that is less well-known, but equally insightful and ahead of its time. In this paper, the authors argued that such refuges might be particularly important foci of adaptive evolution and speciation when they disappear entirely. The argument is that populations might be trapped in refuges and as the habitat continues to deteriorate over time, the populations might have no choice but to adapt or perish. In this way, arguing from the chrysolepis complex as well as from other lizards, dry forest or even grassland species might evolve from wet forest ancestors. This hypothesis could explain the existence of closely-related species occupying very different habitats–the antithesis of what is now known as phylogenetic niche conservatism–and even might explain the parapatric distribution of close relatives if the new species expanded its range (see previous post for more discussion). This idea was published in Papéis Avulsos de Zoologia in 1981 .(download it here) and deserves more attention than it has received.
The Puerto Rican Racer, Alsophis portoricensis. Photo by Donald Gudehus
Sometimes it’s easy to forget that anoles aren’t the only animals in the Caribbean. But, in fact, there are other types, even of reptiles, and some of them have diversified a fair bit (though none, of course, to the extent of anoles). One such group are the alsophiine snakes, formerly all in the genus Alsophis. This Caribbean radiation of racer-like snakes includes at least 43 species ranging in size from 200-2000 mm in length and occupying a variety of habitats.
Recently, Frank Burbrink and colleagues, in a paper in the Journal of Biogeography, have re-analyzed DNA data originally presented by Hedges et al. and have investigated rates of species, morphological and ecological diversification. The phylogenetic tree they recover is very similar to the Hedges et al. phylogeny and indicates fairly extensive within-island diversification. Sounds very anole-like, but it turns out that rate of diversification is quite different. Unlike anoles, species diversification and the evolution of morphological variety putter along a fairly constant rate (with a few statistical twists and turns).
Why the difference? Burbrink et al. postulate that the opportunity for diversification has been just as great for alsophiines as for anoles, so why are the evolutionary patterns different? The authors put forward a number of possible explanations, but none is compelling. Of course, although adaptive radiations often exhibit explosive bursts of diversification, there is no necessity for this to occur, and some very diverse groups have radiated at a more sedate pace. Moreover, one might question why alsophiines haven’t diversified even more–sure, they differ in body size and climatic niche, but how different are they otherwise? And how many species can co-occur at a given locality? Is it just lack of time–one of Burbrink et al.’s hypotheses–or is something constraining alsophiine diversification?
More generally, it would be interesting to conduct similar analyses on other Caribbean taxa–not just reptiles, but also amphibians, birds, even insects and plants–to see what generalities, if any, characterize Caribbean evolutionary diversification.
Photojournalist, anole aficionado and AA has devoted yesterday’s post to the goings-on of her local brown anoles. Check it out Daffodil’s Photo Blog.
httpv://www.youtube.com/watch?v=UR_byRbXxvs
Anole researcher Anthony Herrel showed his true colors recently in a seminar when he said that chameleons are cooler than anoles. Be that as it may, this video is a fun demonstration of the amazing traits that make chameleons the second coolest lizards. It’s part of the “True Facts” series of videos, which are quite entertaining–one episode on tarsiers was featured in a recent AA post.
Here’s a disturbing photo that came across Facebook the other day. And I always thought these katydids seemed like delightful, gentle forest nymphs. Who knew they could be vicious killers. This comes from The Biodiversity Group’s Facebook page, but I couldn’t locate the image on their website, though I didn’t look that hard. They identify the anole as A. princeps but don’t provide any further information.
Anolis tigrinus. Photo by J. Losos.
I’ve previously posted on the surprising behavior of the Venezuelan A. tigrinus. We found them in astonishing abundance in the town of Colonia Tovar, in the mountains above Caracas. Despite their twig anole appearance and their twig anole habitat use–on twigs and other narrow surfaces–they don’t behave like twig anoles. Rather, they move rapidly and often, and seem to display a lot as well. Some Caribbean twig anoles move frequently, albeit slowly, and some display a lot, but none zip around like these guys. Moreover, we’ve seen a number of other mainland twig anoles, and they live life in the slow, slow, slow lane. So, our first day of tigrinus-watching was full of surprises. But that night, things got even more surprising, as I recently recounted in my most recent post in the Scientist at Work blog of the New York Times..
The tell-tale banded tail.
Anolis tigrinus sleeping on a stem. Photo by J. Losos.
As we walked down to the local brewhaus to grab a pizza, we casually scanned our surroundings. And as we walked by a weed patch, there was the tell-tale white blob hanging on to the end of a grass blade. It could be only one thing–an anole. In the Caribbean, this would be primo grass-bush anole habitat, but there were no grass-bush anoles here. Quick examination confirmed that it was an A. tigrinus. That’s right, a twig anole in the grass. And then as we looked around, there were more and more of them–the lot was silly with twig anoles.
The next two days, I came back during the day to look for twig anoles. Unlike in the woods where we had found them initially, the twig anoles here were hard to find during the day, even though the place was full of them at night. The few I saw were deep in the vegetation–my conclusion is that this guys are moving through the vegetation, navigating along narrow branches, stems, and grass-blades.
Which leads, of course, to the question of why in the Caribbean, grass-bush anoles use low-lying narrow vegetation in grassy, bushy areas, while twig anoles use narrow twigs and branches up in the trees. Perhaps A. tigrinus is just being opportunistic, taking advantage of an unoccupied habitat and moving in? Certainly a plausible explanation, but I’ve never, ever heard of a twig anole in the grass in the Caribbean. Has anyone? Not even in Jamaica, where there are no grass-bush anoles.
This in turn reminds me of the trunk-crown anoles, A. allisoni, I observed in the grass in Roatan, Honduras. If nothing else, it’s important to remember that anoles are very behaviorally flexible and adaptable. Even though they’ve specialized to different microhabitats, they aren’t so specialized that they can’t use other microhabitats when they get the chance. Crown-giant anoles on the ground are one example, but that’s another story.
In any case, A. tigrinus is a very interesting anole, and it’s great abundance would make it an excellent choice for behavioral and ecological studies.
Sweet dreams, little tiger anole. Photo by J. Losos
Anole perch height depending on whether it was raining and whether curly-tailed lizards (Leiocephalus carinatus) were observed on the plot.
Do you like standing out in the rain, especially when it’s cold? Me, neither. But that’s what the dastardly curly-tailed lizard forces brown anoles to do. Any sensible, semi-arboreal lizard would come down from the heights and seek shelter when it starts to rain, and that’s exactly what brown anoles do. Except when they’re in areas of high curly-tailed lizard activity, in which case they suck up and stay up high, shivering and being pelted by rain drops. That’s what research by Marta Lopez-Darias and colleagues (among which, yours truly) reported in a recent paper in Ecology. As the figure below illustrates, pretty much the only time the brown anoles drop down is when the weather goes to pot and curlies aren’t around: cool, windy, and very humid–in other words, when it’s raining. But if big boys have been cruising around on the ground, the anoles maintain their high perches.
Brown anole perch height as a function of a variety of weather variables and of curly-tailed lizard activity (in this figure, instead of presence/absence as in the figure above, predator activity was measured as the time-standardized number of active curly-tailed lizards observed on the plot).
All kidding aside, it’s not clear why they come down when it’s raining, but presumably there’s a benefit to it. One can only speculate what that is; my first guess: when it’s wet and cold, anoles are less able to notice approaching predators and less able to get away quickly because of their lower body temperature, hence they seek safer environs. Or perhaps there’s simply no potential prey afoot, and thus no reason to hang out in a high vantage point looking for them. Whatever the reason for doing so, it appears to be overruled by the threat of marauding curly tails.
As for details of the study: ten study plots were set up in various parts of Great Abaco. Plots were regularly censused, tabulating the number of curly-tailed lizards observed, the perch position of each anole observed, and a battery of meteorological variables.