Are Anoles Less Abundant in North Carolina after Last Year’s Cold Winter?

Anolis carolinensis from North Carolina. Photo by Graham Reynolds.

In response to a previous post on North Carolina anoles, AA reader John Philips asks:

Anyone notice a significant reduction in the population of anoles in SE NC? I live on Bradley Creek in Wilmington, NC and I have noticed very few this year. Used to see 3-5 per day sitting on various surfaces in the sun while walking my dogs, especially because my shihpoo is always “hunting” them. However, this year I probably only see 1 per week.

I assume this could be due to the cold winter? Any other predators that might have reduced the population? We have seen an increase in brown thrashers in the area and thought since they forage on the ground they might be a predator?

Anole Outpost: The Cay Sal Bank, Part I

What determines species composition on remote Caribbean islands? Geographic proximity to source populations? The vicissitudes of dispersal and colonization? Propagule pressure and prevailing biotic and abiotic environmental conditions? The study of biogeography addresses such questions, and is concerned with understanding the geography of biodiversity- where do species occur and why?

We perhaps often think of species groups accumulating from colonists arriving from the same place, that is, we identify a likely natal source for island colonists. But might species groups be chimeric, in that they contain groups of diasporic species from different natal lands? This is certainly a plausible scenario and could potentially lead to some interesting evolutionary outcomes.

The Cay Sal Bank is a remote island bank, or shallow carbonate platform, on which rests a line of small islands strung out along its margins. This region, as well as our recent expedition, has been mentioned in a previous AA post. Here I am returning to discuss the anoles and the results from our recently published work describing the evolutionary relationships of the terrestrial squamate fauna. Fundamentally, we ask a question that has circulated for the better part of a century: where do the anoles on Cay Sal come from?

Six terrestrial squamates are found on this bank:
Anolis fairchildi (endemic)
Anolis sagrei
Tropidophis curtus
Sphaerodactylus nigropunctatus
Cubophis cantherigerus
Typhlops biminiensis

Dispersal hypotheses for terrestrial squamates found on Cay Sal Bank, from Reynolds et al. 2018

Of these, all but Anolis fairchildi and the recently discovered population of Cubophis were thought to have Bahamian evolutionary affinities. The endemic A. fairchildi has been of particular interest, owing to its status as the product of one of the ex situ speciation events occurring in the green anoles as they dispersed from Cuba (Williams 1969). But a previous AA post (1) reminded us that the origins of Anolis fairchildi had not been resolved- did they come directly from Cuba or are they derived from Bahamian A. smaragdinus (among other alternatives?). Here we tackle this question, using a basic mitochondrial dataset and lots of taxon sampling from previous study of the group (more on A. fairchildi in a future post). We constructed a coalescent gene tree of all “carolinensis-clade” Cuban green anole species, including our samples obtained from Cay Sal Island in 2015. We find unequivocally that A. fairchildi is a recent colonist from western Cuba- nested within the western Anolis porcatus lineage. Thus we see both ancient and recent emigration (divergence) events leading to what we recognize as species in the carolinensis clade of green anoles, setting up a really nice opportunity to examine the accumulation of variation in diasporic populations over different time periods.

Phylogeny of “carolinensis clade” green anoles from Reynolds et al. 2018, with A. fairchildi highlighted in green and shown in the inset photo

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.

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