Category: New Research Page 58 of 66

Female Anolis polylepis. Photo from http://www.wildherps.com/species/A.polylepis.html

In many species of anoles, females within a population exhibit sometimes strikingly different back patterns. A recent paper showed that there is interesting variation in the incidence of such variation: mainland and Lesser Antillean anoles exhibit it much more than Greater Antillean anoles, and within regions, some clades are more polymorphic than others. Although closely related species tend to be similar, this trait has been evolutionarily labile, evolving an estimated 28 times.

The occurrence of this variation raises the question: what’s it for? The most detailed study of the question was Schoener and Schoener’s examination of female polymorphism in Anolis sagrei in the Bahamas. By looking both within and between populations, they concluded that this polymorphism was related to crypsis. In particular, females with stripes tend to occur on narrow diameter branches, where the stripes help them blend in. Calsbeek and Cox have more recently examined the same species, finding most recently that different patterns don’t seem to vary in fitness, though they did not examine whether females with different patterns occurred in different parts of the microhabitat.

The only other recent work on this topic was conducted on A. polylepis in Costa Rica by Steffen.

Reproductive Cycle of a High Elevation Colombian Anole

By Jonathan Losos

On October 16, 2011

In New Research

Anolis mariarum from https://www.facebook.com/media/set/?set=a.111687092219097.16289.111684688886004&type=1

Brian Bock and colleagues, most at the Universidad de Antioquia in Medellin, Colombia, have published a series of papers on two populations of the high elevation anole, Anolis mariarum. The most recent in this series, just out in the journal Caldasia, is an examination of the reproductive cycle of this species.

In Central America, many anoles that occur in areas with a single long dry season curtail their reproduction during the dry times. However, A. mariarum occurs in areas where there are two wet and two dry seasons over the course of the year, and this species breeds year round, as does another highland anole in a similar place climatically, A. (Phenacosaurus) heterodermus. The authors suggest that because each of the dry times are shorter than one long dry season, these species are able to continue breeding. But, as the authors note, a confounding factor is that these two species occur at very high elevations (> 2200 meters), where temperatures are much cooler than most species that have been studied. Despite a considerable amount of work on anole reproductive phenology, there is still much to learn.

Monkey Eats Polychrus

By Jonathan Losos

On October 14, 2011

In New Research

What have I done? Capuchin monkey photo https://www.anoleannals.org/wp-content/uploads/2011/10/capuchinmonkey011.jpg?w=300

Sure they’re cute, but in reality they are anole-killing machines. Well, maybe that’s an exaggeration, but at least some monkeys will eat just about anything, and I was once told of a capuchin that caught a large anole (A. frenatus), held it by its hindparts and smacked its head repeatedly against a branch to dispatch it, and then ate it. This is why life is so tough for mainland anoles–there are so many critters out there trying to eat them.

Any way, that brings me to the subject of this post. In a recent Natural History Note in Herpetological Review (Vol. 42, pp.432-433), Cassimiro and Pereira Martins report an observation of a crested capuchin monkey (Cebus robustus) eating a Polychrus marmoratus, which ironically has the common name of “monkey lizard.” Although we now know that Polychrus is not the sister group of anoles, still, if a monkey’s eating monkey lizards, it’s probably eating anoles, too. And, in any case, we at Anole Annals are not going to discriminate against the poor monkey lizards just because they’ve lost their special status as almost-anoles, and hence we will continue to report from time to time on late breaking developments in the monkey lizard world.

Have You Seen Anoles Play Dead?

By Jonathan Losos

On October 11, 2011

In Natural History Observations, New Research

Baby Anolis distichus playing dead. See comment by Hispanioland.

John Phillips and Kirsten Nicholson report in Herpetological Review (42:426-427) observations on A. laeviventris and A. cupreus. To wit: “Upon capture, the individuals struggled to escape the grasp of one of the authors (JGP), and then suddenly went limp without further pressure being applied. In this state, both individuals exhibited the same body position: jaw wide open, dewlap extended, hind legs out, forelegs bent in over the venter….but when the grip was loosened, the individuals immediately sprung to life and escaped.”

The authors note that similar behavior has been recorded in several other species. Any one else seen this? Is it a widespread, but under-reported, natural behavior of anoles?

What’s All the Fuss About Dewlaps?

By Jonathan Losos

On October 8, 2011

In New Research

: Anolis carolinensis from http://www.mascotissimo.com/wp-content/uploads/2008/02/anolis_carolinensis.jpg

A few years ago, Richard Tokarz and colleagues conducted a series of studies in which he surgically disabled the dewlaps of some male A. sagrei and discovered that these functionally dewlapless lizards had no trouble holding a territory and seducing females. In a new study, Henningsen and Irschick found that surgically reducing the size of dewlaps in male A. carolinensis by about one-third had no effect on male-male aggressive interactions in the lab. Makes one wonder what’s the big deal about having a dewlap.

Anole Genome Paper in Print and Freely Available Online

By Jonathan Losos

On October 2, 2011

In New Research

In this day of online publication of papers, the significance of the actual appearance of a journal’s latest issue, with an article right there, in ink on paper, has greatly lessened. Nonetheless, I, for one, still consider that moment to be the official publication of a paper. And in that vein, the anole genome paper officially appeared in this week’s issue of Nature. It’s freely downloadable here.

Dewlap Color, Gene Flow, Habitat Specialization, and Speciation: A Tale of Two Contact Zones

By Jonathan Losos

On September 29, 2011

In New Research

Dewlap variation in Anolis distichus in Hispaniola. The photos at the bottom show the change in dewlap color along the two transects in the recent study by Ng and Glor.

Despite all of the research on anole evolution conducted in the last 40 years, one important question still eludes us: how does speciation in anoles occur? This, of course, is of fundamental importance, because the great species richness of these lizards implies that speciation has run rampant in this group. So, we’d like to know why.

We don’t know much about speciation in anoles, but we do know a little. First, it is thought that the dewlap plays an important role. Sympatric anole species almost never have identical dewlaps, and experimental and observational evidence suggests that anoles use their dewlaps for species-recognition. Hence, understanding anole speciation may, to a significant extent, reduce to understanding the factors that cause populations to evolve differences in their dewlaps.

A different perspective on anole speciation relates to the classic question of whether allopatry is necessary or whether, as suggested by many recent studies, natural selection driving differentiation—whether in allopatry or not—is a more important stimulus to genetic differentiation. Recent work in the Lesser Antilles by Thorpe and colleagues has argued that environmental differences are the primary drivers of genetic differentiation within anoles, a result also suggested by Leal and Fleishman’s studies on A. cristatellus in Puerto Rico.

In this light, perhaps the most enigmatic anole is Anolis distichus of Hispaniola.

Perch Compliance and Dumb Luck

By Casey Gilman

On September 26, 2011

In New Research

Thanks to Duncan Irschick’s insistence that I start a project immediately upon my arrival in the PhD program at UMass, Amherst (and inspiration from a passage in Lizards in an Evolutionary Tree stating that the effects of perch instability on anole locomotion had not yet been examined – thanks, Jonathan!), I spent part of the summer of 2011 studying the effects of perch compliance (flexibility) on green anole ecology and jumping performance in the wild. This followed my examination of the effects of this perch characteristic in the lab over the last two semesters (manuscript under review).

However, finding an ideal field site for this study proved a bit more challenging than I had anticipated. Yoel Stuart invited me to work with him on a project examining the effects of interspecific competition on diet in Anolis carolinensis and A. sagrei using stable isotope analysis last summer (we continued this project through 2011), and I based my vision of an ideal field site on my experiences watching green anoles hop and run around on slender (and quite flexible) mangrove branches. I envisioned a site with plenty of small to medium diameter branches and larger trunks for the anoles to frolic on, which would provide me with plenty of data on how these lizards use compliant perches in the wild.

After a FULL week of searching (with plenty of field site advice from Yoel), I settled on a site with the type of habitat structure I had originally been seeking, as well as many small cabbage palms (< 3m) along the forest edges.

Measuring Bite Force In Anoles: The Video

By Jonathan Losos

On September 21, 2011

In New Research

The latest anole flick from Day’s Edge Productions. If you haven’t seen some of their previous work, try this one. And for an interview about this film with filmmaker and UCLA grad student Neil Losin, go here.

The Evolution of Female Pattern Polymorphism

By Jonathan Losos

On September 17, 2011

In New Research

In many species of anoles, females vary in their back patterning, some gaudily adorned with saddles, diamonds, or crosses, others sporting simple lines and speckles, some sad lasses with no markings at all. Although such female pattern polymorphism has long been noted and its adaptive significance studied (for example, here), no one has compiled a list of which species exhibit it and which don’t, much less examined patterns of FPP evolution.

Until now. In a very nice paper, Paemelaere et al. have surveyed the literature and recorded the presence or absence of of FPP in 179 anole species. They find a wide variety of interesting findings. First, there is phylogenetic signal: closely-related species tend to be similar in the presence or absence of FPP. Nonetheless, second, FPP has evolved and been lost many times—overall, at least 28 evolutionary transitions, with more gains than losses. The ancestral condition, incidentally, appears to be an absence of FPP. Third, there is great biogeographical heterogeneity (see figure above). FPP is far-and-away most common among mainland anoles, and is also reasonably common in the Lesser Antilles, but much less common in the Greater Antilles. Within the mainland anoles, it is particularly members of the Norops club that have FPP; much less among dactyloids. However, Norops also occurs on Cuba and Jamaica, and there they don’t exhibit much FPP.

One additional interesting pattern not remarked upon by Paemelaere is that among Greater Antillean species, FPP occurs primarily in trunk-ground anoles, having evolved at least three times independently on different islands (in three members of the sagrei clade on Cuba; A. cristatellus on Puerto Rico; and three members of the cybotes clade on Hispaniola).