Year: 2013 Page 14 of 37

Why do closely related species sometimes differ in signalling behaviour, despite apparent similarities in the selection pressures that act on the signal? That question is addressed in a paper in Functional Ecology now available as an early view.

Comparing Anolis species from Jamaica that extend the dewlap rapidly with more slowly extending relatives from Puerto Rico, Ord, Collar and Sanger have modelled the performance of the dewlap and then simulated changes to the system to predict its effects on the speed of the dewlap extension. The predictions are then compared with data on both morphology from cleared and stained specimens and actual dewlap speeds for lizards recorded in the field.

The analyses show that morphological changes have affected the performance of the dewlap display in Jamaican and Puerto Rican anoles differently. Within islands structural changes have led to differences in dewlap speed among species, whereas differences between islands are the result of an increase in muscle contraction velocity present in Jamaican species, but absent in Puerto Rican species.

The study is an excellent example of how investigations into the biomechanics of motion-based visual displays can increase our understanding of differences in signal behaviour.

The 50th annual conference of the Animal Behavior Society kicks off today in Boulder, Colorado. Anole presentations are few: only two posters, which begs the question, why aren’t more behavioral biologists studying anoles? Certainly, their behavior is easily observed and manipulated. And, indeed, some such work is conducted, but not nearly as much as one might expect given the ubiquity of the animals in the southeastern U.S. and throughout the neotropics. And, moreover, the behavioral work that is done is relatively infrequently published in the behavior literature or, apparently, reported at behavior meetings. Behaviorists, you’re missing the boat!

In any case, the sole anole reporter at ABS is Joe Macedonia, who is presenting two posters. The first is a comparison of the behavior of the odd gray-dewlapped green anoles with more ordinary, red-dewlapped populations, and the second is a study using anole robots to determine the relative importance of dewlap color and behavior in species recognition; this study has recently been published and we should be hearing more about it soon.

A Comparison of Headbob Display Structure in Gray-Dewlapped and Red-Dewlapped Anolis carolinensis

JM Macedonia, LE Cherry, DL Clark

Many species of diurnal lizards engage in motion displays, termed ‘pushups’ or ‘headbobs’. In the diverse genus Anolis, headbob display structure typically exhibits substantial interspecific, and in some cases population-level, variation. The green anole (Anolis carolinensis) exhibits a red-dewlapped (RD) form found throughout the southeastern USA, as well as a gray-dewlapped (GD) form that is restricted to southwest Florida. Prior research has shown that RD A. carolinensis produce headbob displays of three basic types (Type A, B, C) that vary primarily in display unit durations. Based on known genetic and physiological differences between the two dewlap color forms, we hypothesized that GD and RD males also would differ in headbob display temporal structure. We quantified 440 displays from 24 GD and 15 RD males, and found some, though not all, display units to differ significantly in duration between the two populations. Our results therefore indicate that stereotyped display behavior can be added to the list of known traits that differ between the gray-dewlapped and red-dewlapped forms of A. carolinensis.

Color and motion display discrimination in Anolis grahami: evidence from responses to lizard robots

JM Macedonia, DL Clark, DJ Kemp

Anolis lizards exhibit color and motion displays that are thought to mediate species recognition, but direct experimental support is limited. We used lizard robots in two field experiments to test the relative importance of dewlap color (calibrated using a computational visual model) and headbob display structure for species recognition in Anolis grahami on Bermuda. Results from experiment 1 revealed equivalent, significant decrements in responsiveness of 102 adult male subjects to color and motion display manipulations, relative to the conspecific robot control. Findings also suggested that dewlap hue, not brightness, was responsible for reduced subject response to non-control dewlap colors. In experiment 2 we presented 93 different A. grahami males with conspecific or heterospecific (Anolis extremus) robots that performed their own, or the other species’, headbob displays. Results revealed species-specific body/dewlap coloration to be more important than headbob display structure for species recognition. Although more work is needed, our findings support the proposition that interspecific variation in color and motion displays provides important cues for species recogntition in anoles.

Mark Yokoyama’s second edition is now out, and available for download for free. Or, if you want to go old school, hard copies are available for purchase on Amazon.

The 128 page guide covers both the native and introduced fauna of Saint Martin, with more than 500 photographs and considerable treatment of invertebrates as well as vertebrates.

Of course, the most important subject of the book are the anoles, two native and two introduced, each of which gets a page. Mark has published previously on the introduced anoles, A. sagrei and A. cristatellus. Both for the moment are restricted in range–to a resort complex and a cruise ship terminal,  respectively. If they expand their ranges–and I’m betting they will–it will be interesting to see how they interact with the native A. gingivinus, as well as each other.

The image below on A. pogus will give you a feel for the book. Certainly a must-have if you’re going to St. Martin, and a nice-to-have even if you aren’t.

Cophotis ceylanica. Photo by M. Wickramasinghe

It’s got a dewlap, too!

Those upstart Asian agamids are at it again, trying to out-anole anoles. We’ve already marveled at the dewlap of Sitana and its friends, which—I hesitate to say this—makes any anole dewlap look bland by comparison. Now can we all agree that this guy here, Cophotis ceylandica, is a twig anole’s twig anole?

Any way, the photo comes from a new paper that reports an observation of a jungle crow in a Sri Lankan park catching one of these guys, tearing it in half (grutesome!) and then eating it. And then it did it again three more times in the next half hour, two more C. ceylandica and a third, unidentified lizard. This was just one bird in a flock of 37, and guards at the park say they are quite prolific lizard catchers. The authors make the interesting point that jungle crow populations in the park appeared to have grown as a result of all of the garbage, and an incidental victim of this may be lizard populations.

German speakers, we need you again. Can you look at the attached paper and confirm that the two parts are German and English versions of the same text?

In an interesting new paper in the journal Checklist (subtitled, the “journal of “species lists and distribution”), Bienentreu et al. report on 28 new specimens of A. salvini from western Panama.  On its face, the paper is simply a description of many new specimens of a little known species. But lurking within are a variety of fascinating tidbits.

First, A. salvini is a member of the pentaprion clade of twig anole-like mainland species. The authors note that previous work by Köhler subsumed A. vociferans into A. salvini, but no one seems to have noticed—maybe this paper will help.

Second, and perhaps most interesting, the authors note extensive variation in dewlap color within this species, as illustrated in the figure above: e-h are males, and i-l are females.This variation is striking and worthy of further investigation.

Lastly, third, the authors note that the species vocalizes when handled, and even provide a spectrogram. Very few anoles make sounds, a topic which has received very little attention.