Oxpeckers of the Caribbean: Anole Dines on an Iguana

Guadeloupean anole (Anolis marmoratus) feeding on the back of a Lesser Antillean iguana. Photo courtesy Jérôme Guerlotté.

Jérôme Guerlotté of the Muséum National d’Histoire Naturelle in Paris reports:

“As in a new Jean De la Fontaine fable “L’iguane et l’Anolis“, this intrepid anole (Anolis marmoratus marmoratus) on Guadeloupe had just hunted a fly on the back of this Lesser Antillean iguana (Iguana delicatissima) (top) and rids it of small insects on the snout (bottom).”

Who knows what yummy morsels reside on the snout of an iguana? Photo courtesy Jérôme Guerlotté.

Anole Annals World Cup: Round One

It’s June. It’s orchid flowering season in Grand Cayman. And with nods to #Anole March Madness and  #MammalMadness it’s the opening round of the 2018 ANOLE WORLD CUP. #ANOLEGOOAAAAALLLL!!!!

Home Team – Anolis conspersus  – against –  Away Team – Anolis sagrei

And in less than 90 seconds it’s all over.


The teams are on the pitch

 


The Away Team

 


The Home Team heads to mid-field

 

 


The Striker takes aim

 


Home Team – 1, Away – nil

 

 

 

 

 

 

 

 

Brown Anoles Invade Europe!

Reporting from Germany where she was leading a course on Transposable Elements, Jessica Stapley  — of mainland anole fame — posted this picture to Twitter. It appears brown anoles (A. sagrei) have set up a new home in one of the greenhouses at Berlin’s Botanical Gardens!

There are reports of un-established populations of green anoles (A. carolinensis) in southern Spain and the Canary Islands (reviewed here), as well as a report of Cuban knight anoles (A. equestris) also on the Canary Islands.

Does anyone know of other European records of anole populations?

 

An Experimental Test of Whether Dewlaps Are Adapted to Increase Detectability

Anolis krugi. Photo by Manuel Leal from the Leal Lab webpage

Anole biologists are fascinated by the variation in dewlap colors and patterns both within and between species. One popular hypothesis is that dewlaps are adapted to be easily detectable against the background in which they are found. A variety of tests have been published, correlating dewlap colors with ambient light, background vegetation and other characteristics. Now Alex Gunderson and colleagues have developed an experimental method of directly testing the hypothesis. Manuel Leal, a coauthor on the paper, reports on the pages of Chipojo Lab, reprinted here:

Brighter is not always better

Those that follow the Chipojoblog are familiar with one of our core tenets: strive as best you can to design experiments under natural conditions. This philosophy reflects my own view that behavior should be studied in the field whenever possible. Our recent paper in Current Zoology, “Visual playback of colorful signals in the field supports sensory drive for signal detectability,” is a prime of example of the power of this approach, in which an intimate understanding of the ecology and behavior of anoles was used to test a major prediction of the sensory drive hypothesis: are signals locally adapted? In other words, are dewlaps locally adapted to effectively grab the attention of an inattentive receiver?

Over the years we have published a series of papers supporting the hypothesis that dewlap diversity can be partially explained by selection to increase the probability of detection. However, until this paper, experimental evidence from the field was missing, in part because manipulating dewlaps of live anoles is not trivial. Furthermore, even if we were able to successfully manipulate dewlaps, there are still many other signals (e.g., body color, motion pattern, size and posture) that would be out of our control. This problem was solved by researchers working with acoustic signals a long time ago by figuring out ways to play the signal of interest in isolation in what have become known as ‘playback experiments.’ We stole a page from their book and constructed a remote-control dewlap apparatus, which provided an opportunity to display only the dewlap under natural conditions (see gizmo below).  Alex’s building and painting skills was key to the success of this gizmo. He was able to construct dewlaps with similar reflective and transmission properties of real dewlaps while taking into account the visual system of the anoles (please see papers for details).

Control-remote dewlap display apparatus. A) Acrylic box within which electrical components were housed. B) Electrical components. C) The apparatus at a mesic site with a fake dewlap displayed.

Besides presenting the dewlaps in the field, we wanted to test the hypothesis that the dewlaps are locally adapted. Under this hypothesis, increased detection in one habitat comes at the cost of decreased detection in another habitat. This functional approach to test for adaptive value of a trait is commonly used as robust evidence to support selection favoring the evolution of the trait in question. In this paper we tested if the observed differences in dewlap brightness between xeric and mesic populations of Anolis cristatellus is adaptive. If so, dewlaps from mesic populations should be more detectable in mesic habitats and dewlaps from xeric habitats should be more detectable in xeric habitats. Furthermore, detection probability should decrease in the ‘wrong’ habitat. Below are the results of the experiments.  In A. cristatellus individuals from xeric habitats have dewlaps which are darker, that is less brighter,  than individuals from mesic populations.

Responses of free-ranging A. cristatellus to fake dewlaps that mimic the brightness properties of real dewlaps.

Our findings support the sensory drive hypothesis and strongly suggest that the brightness  properties of A. cristatellus dewlaps are locally adapted via selection on signal detectability.  Furthermore, we have demonstrated that a brighter signal is not always the most detectable or effective signal. A common misconception, which is partially the result of not including the sensory system and habitat conditions as part of the analysis. Studies addressing potential functions and selective forces promoting the diversity of dewlaps found in anoles have flourished over the last decade,  nevertheless, these results are the best experimental evidence that we have to support the hypothesis that diversity of dewlap colors might be partially explained by local adaptions to habitat light conditions and the best smoking gun to support the idea that diversity of dewlap colors can be the result of local adaptations to habitat light conditions.  Additionally, our study once again underlines the need to measure both reflection and transmission when asking questions regarding the potential function of the dewlap because the two combine to determine dewlap coloration (brightness, coloration, etc.) in the real world.

Google Loves Anoles!

Ever been tempted to buy a Google Pixel cellphone? Well now you might have extra incentive! 

 

To highlight how a Google Pixel may lead you on an adventure, Google highlight’s its new photo identification feature — Google Lens — with a picture of a brown anole!

Now…how do we convince Google to give us all brand new cellphones sponsor us…?

 

HerpHighlights Podcast: an Assortment of Anoles

HerpHighlights is a Podcast run by Tom Major and Ben Marshall in which they discuss recent advances and interesting news on reptile and amphibian behavior, ecology, and conservation.

This podcast is now live and you can listen to it by clicking the link below:

https://herphighlights.podbean.com/e/026-assortment-of-anoles/

In this episode, Tom and Ben discuss many interesting research topics – both new and old – involving anoles. Notably touching on Kamath & Losos’ recent commentary on the mating systems of brown anoles (A. sagrei) in Florida, as well as Medina et al.’s review of the evolution of dorsal patterning across Caribbean anoles.

Check it out!

Kamath, A, and JB Losos. 2018. “Estimating Encounter Rates as the First Step of Sexual Selection in the Lizard Anolis Sagrei.” Proceedings of the Royal Society B: Biological Sciences 285 (1873): 20172244.

Medina, I, JB Losos, and DL Mahler. 2016. “Evolution of Dorsal Pattern Variation in Greater Antillean Anolis Lizards.” Biological Journal of the Linnean Society 120 (2): 427–35.

 

Drivers and Constraints of Within-Species Diversity in Dewlap Design

Sampling locations of the populations of study across the Caribbean. (1) Soroa (Cuba), population 1; (2) Soroa (Cuba) population 2; (3) Grand Cayman; (4) Santa Clara (Cuba); (5) South Bimini; (6) Chub Cay; (7) Andros; (8) Crooked Island; (9) Acklins; (10) San Salvador; (11) Staniel Cay; (12) Pidgeon Cay; (13) Grand Bahama; (14) South Abaco; (15) Cayman Brac; (16) Little Cayman; (17) Jamaica.

The dewlap is arguably one of most fascinating features of anoles. For me, it is the baffling diversity in dewlap size, coloration, and use —both among and within species— that makes it so interesting. However, understanding the origin and evolution of dewlap diversity in Anolis has proven a daunting task (Nicholson et al. 2007; Vanhooydonck et al. 2009). In an attempt to make (a little more) sense of the drivers and constraints of anole dewlap variation, a team of Belgian researchers from the University of Antwerp, led by evolutionary ecologist Tess Driessens, decided to look at dewlap diversity in Anolis sagrei. They surveyed 17 island populations of A. sagrei across the Caribbean and quantified dewlap design (color, size) and dewlap display behavior of both males and females.

Last year, Driessens and colleagues published their findings on how variation in abiotic factors (such as precipitation, temperature and other climatic variables) could explain much of the observed inter-island variation in dewlap design and use in A. sagrei (‘signal efficacy’ hypothesis). In a paper that came out last week, the team reports on the role of the biotic environment in driving dewlap diversity in the brown anole. Inspired by the wonderful study of Vanhooydonck et al. (2009), the researchers tested whether among-population dewlap variation could be (at least partially) assigned to variation in predation pressure (estimated by island size, tail break frequency, presence/absence of the predatory curly-tailed lizards, clay model attack rate), sexual selection (using sexual size dimorphism), and/or species recognition (number of syntopic Anolis species). Overall, they found only limited support for the idea that the extensive interpopulational variability in dewlap design and use in A. sagrei is mediated by variation in their biotic environment. Although they did find that males from larger islands show higher dewlap display intensities than males from smaller islands, and that males are more likely to have a ‘spotted’ dewlap pattern when co-occurring with a high number of syntopic Anolis species, the direct connection with predation pressure and species recognition remains ambiguous and demands further investigation.

In another recent paper, focusing only on the size of the male dewlap and their maximum bite capacity, the Belgian researchers asked a different question: does dewlap size signal fighting capacity (estimated by bite force) in A. sagrei, and is this true for all 17 sampled populations? And, does the level of signal honesty (that is, the steepness of the dewlap size-bite force relationship within a population) vary among populations, and is it linked with the strength of intrasexual selection? Their results showed that absolute dewlap size is an excellent predictor of bite force in all A. sagrei populations. However, relative dewlap size was only an honest signal of bite performance in 4 out of the 17 populations. Surprisingly, the level of signal honesty did not correlate with the strength of intrasexual selection.

Male brown anole biting on a purpose-built force plate. Photo by Tess Driessens

While the work of Tess Driessens and her team sheds new light on the drivers and constraints of dewlap diversity in A. sagrei, there is still plenty of study material left for future dewlap fanatics.

Sometimes Knights Eat Dragons (Dragonflies, That Is!)

One of the loudest anole meals I’ve witnessed.

During one recent afternoon’s field work, I heard an unusual noise in the botanical garden I was working in: a sound like someone crunching and crinkling a foil potato chip bag. Tracing the sound from about 20 feet away, I did not find a snacking plant enthusiast, but rather a young Knight Anole (Anolis equestris) in survey posture who had apparently just snagged a large dragonfly out of mid-air. The anole chowed down on its prey while keeping a weather eye on me and conducting a few half-hearted displays to let me know it was aware of my presence. As the anole continued to masticate its rather large afternoon meal, it moved to a higher perch away from the prying eyes of this anolologist.

The dragonfly, a Regal Darner (Coryphaeschna ingens), is a common species in the southeastern United States and an accomplished aerial predator. It was also more than a mouthful for this young knight, which had to chew with its mouth open for over four minutes (and still wasn’t finished when it escaped my view); quite the prey handling time! And yet more evidence that this largest of anole species is willing to take a chance on any prey item that might fit into its maw even if it takes a little work.

An impressive snag for such a young anole.

Can Evolution in Brown Anoles Keep Pace with Climate Change?

A male brown anole from the island of Great Exuma in The Bahamas.

Human-caused climate change is rapidly changing the thermal environments experienced by many species. Most ectotherms, like many of our beloved anoles, maintain small home ranges and are therefore assumed to lack the ability to disperse over long distances. If they can’t migrate to thermally suitable areas, how will anole populations deal with climate change? A major theme emerging in the literature is that evolutionary adaptation may be one of the primary ways that anoles compensate for rapid environmental change.

In close collaboration with many other people, my recent work has focused on thermal adaptation in the brown anole (Anolis sagrei) from The Bahamas. Our early findings suggested that this species may be able to rapidly adapt to changing thermal environments. For example, we found that the thermal optimum for running speed (the “thermal performance curve”) was locally adapted in populations living on a series of thermally variable cays in The Bahamas. Populations were locally adapted despite high levels of gene flow across the archipelago, suggesting that selection is constantly weeding out maladapted genotypes as they arrive and favoring individuals whose thermal biology matched local conditions. We also tested this idea experimentally by transplanting brown anoles from a cool, forested environment to a sun-baked peninsula and tracking (through mark-recapture) which individuals survived and which perished. The peninsula was much warmer and more thermally variable than the ancestral environment, and we were able to show that strong selection favored individuals with higher thermal optima and broader thermal tolerances on the peninsula. While these studies suggested that there is potential for evolutionary adaptation to future climate change, a major question was left unanswered: is there sufficient genetic variation underlying thermal traits such that populations could evolve rapidly? If a trait is not heritable, it will not evolve, and surprisingly few studies have measured the additive genetic basis of physiological traits in lizards.

To answer this question, we captured adult brown anoles from the same two populations involved in our previous transplant experiment (lizards from the islands of Eleuthera and Great Exuma in The Bahamas), brought them back to Bob Cox’s lab at the University of Virginia, and conducted a common-garden breeding experiment. First, Bob raised hundreds of offspring from these two populations, which were native to environments that differed dramatically in their thermal properties. The environment on Eleuthera was much warmer and more thermally variable than the environment on Exuma, so if genetic adaptation had occurred, the offspring of these populations should differ in their thermal physiology when raised in an identical environment, and the differences should be congruent with our previous estimates of natural selection. Interestingly, we found that these populations differed in every aspect of thermal physiology that we measured, but only some of these differences matched our predictions. For example, Eleuthera offspring had higher thermal optima for running speed (predicted to occur based on the warm environment they came from), but lower performance breadths (the opposite of what we predicted because the site on Eleuthera is more thermally variable).

Next, to understand the potential for rapid adaptation to future climate change, we used the pedigrees of the breeding colonies to estimate the additive genetic basis (i.e. heritability) of both the thermal sensitivity of running speed and several aspects of thermoregulatory behavior. For the latter, Don Miles introduced hundreds of Great Exuma individuals to a thermal gradient and measured how they behaved in the gradient. Though the results were somewhat variable, the bottom line is that we found very low heritability in most aspects of thermal physiology and thermoregulatory behavior.

The thermal sensitivity of running speed differed between brown anole populations from the cooler island of Exuma and the hotter island of Eleuthera, even when we raised hatchlings in an identical environment, suggesting that the populations have genetically diverged. Peak running speed for Eleuthera lizards occured at warmer body temperatures, and Exuma individuals ran faster at all body temperatures measured other than the lowest. This figure is copied from Logan et al. (2018).

In general, our results suggest that these populations have adapted to divergent thermal environments in the past, but lack the capacity to evolve rapidly into the future. This could be because strong selection has reduced genetic variation in thermal traits by fixing locally adapted alleles in each environment. Or in the case of the thermal performance curves, it is possible that precise thermoregulatory behavior has removed the need for alleles that confer broad thermal tolerance, leading to mutational decay of those genes. Whatever the cause, we now have evidence to suggest that some thermal traits in brown anoles lack the capacity to evolve rapidly.

There are a number of caveats that go along with our study. First, our sample sizes (Great Exuma = 289, Eleuthera = 119) are modest as quantitative genetic studies go. That fact combined with the difficulty of getting precise estimates of physiological and behavioral traits means that our study should not be considered the final word on the evolutionary potential of thermal performance curves or thermoregulatory behavior in brown anoles or any other species. Second, brown anoles are one of the most successful species on the planet. Indeed, they are extremely common in their native range and have invaded much of the Western Hemisphere. This is not a species that appears to have trouble conquering novel thermal environments, so in no way are we suggesting that they are particularly vulnerable to climate change. In fact, our data suggests that they are likely using behavioral adjustments or phenotypic plasticity to adapt to novel environments, and if anything testifies to the fact that within-generation physiological adjustments can be an extremely powerful tool for mitigating the effects of climate change. Lastly, there are a number of traits we did not measure. What about the critical thermal limits? What about the thermal sensitivity of other performance traits like digestive efficiency, endurance, and bite force? What about thermoconforming species that live deep in forests and have different thermoregulatory strategies and physiological tendencies? There is a lot of work left to be done before we know the full evolutionary potential of anoles under rapid climate change.

The work I’ve discussed here resulted from the efforts of a number of hard-working scientists, including Ryan Calsbeek, Bob Cox, Joel McGlothlin, Don Miles, Katie Duryea, John David Curlis, Anthony Gilbert, Albert Chung, Orsolya Molnar, and Benji Kessler.

Anole Dewlapping at Bird? Part of the Fauna “Visiting” Camera Traps

Camera traps have been placed in front of some karst solution holes in the dry-transition forest of the southern slopes of the Sierra de Bahoruco, in the Pedernales province, Dominican Republic.

The holes hold water after rains, making it one of the very few spots where water is available in that forest (no surface rivers or marshes around). These holes are visited by a variety of animals, which include herps like whiptails, curlytails, racers, iguanas, and other rarities like the solenodon, and many birds.

I wanted to share this photo, since in it is the first anole recorded, an Anolis strahmi, which seems to be displaying at a nearby bird (Ovenbird, placed at extreme right of the frame).

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