An iguanito. Photo from the Coastal Star.
A nice article in the Coastal Star just reported on the spread of knight anoles through Florida. The article contains numerous nuggets, such as quotes from the Florida Fish and Wildlife Commission stating that they’re worried about bigger things (e.g., pythons, tegus), that they’re locally called “iguanitos,” and that iguanas are rebounding from freeze-caused mortality in the recent past and are mainly a problem for pooping by people’s pools.
Macho de Anolis huilae acechando una presa.
Observaciones realizadas en mi finca (Ibagué – Colombia) de un macho de Anolis huilae acechando su presa y una hembra predando su presa. He tenido la oportunidad de observar individuos de ésta especie cazando orugas, larvas y moscas y, la manera como ellos invierten algún tiempo para acechar a sus presas para capturarlas . Aún se desconoce la dieta exacta de esta especie de lagarto endémico de la cordillera Central de Colombia.
Predación por parte de una hembra de Anolis huilae
Editor’s note: Google translates the passage above as follows. It’s amazing how good this programs are getting!:
Observations made on my farm (Ibague - Colombia) of a male Anolis huilae stalking his prey and a female predating its prey. I have had the opportunity to observe individuals of this species hunting caterpillars, larvae and flies and how they spend some time to stalk their prey to catch them. The exact diet of this species of lizard endemic to Central Cordillera of Colombia is still unknown.
Championship round, lightweight division. Photo from Daffodil’s Photo Blog.
We periodically post pictures, videos and stories of male anoles duking it out with each other [e.g., 1,2], but over on Daffodil’s Photo Blog is evidence that such squabbling starts at a young age. Check out how the little fellas, with barely a dewlap to speak of, nonetheless behave just the same as their elders.
Last week, Yoel Stuart and colleagues (including me) published a paper demonstrating that green anoles had rapidly (ca. 20 years) evolved an increase in toepad size as a result of upward shifts in habitat use caused the presence of brown anoles.
The Discovery Institute, an organization devoted to the advocacy of creationist views, posted a blog yesterday saying, basically, “this is not news?” After summarizing the study, here’s what they have to say:
“….these scientists found that when a new species of lizards invaded another’s territory (in fact the new species was placed there intentionally by the researchers, meaning they weren’t quite studying “natural” selection), the old one sought higher ground. That seems like a smart thing to do. To go along with the new territory, they subsequently evolved “larger toepads (see here for a picture).
After reading this, what I really wanted to see was the precise sizes of the toepad and compare the changes. But alas that information is not in the paper. I tried downloading the supplemental materials but it’s not there either. So let’s assume that the toepad size changed a lot. What have we shown?
Not much. We’ve seen that the size of lizard feet can change in response to invaders’ driving a species to perch at higher levels in the trees. No new traits arose. Only the size of a pre-existing trait changed. Again, that’s interesting but such changes in the size of lizard feet do very little to explain the origin of lizards in the first place, even if these changes happen in just a few generations.
If we take seriously the statement from the authors that the modest results from this study can help test “evolutionary hypotheses about phenomena … on time scales too long for direct observation,” then that implies that over long periods you might be able to change the size of an organism or some of its body parts. Since when is that news?”
Not many anoles have blue dewlaps, so we were delighted to see Ann Stafford’s tweet of this lovely conspersus from Grand Cayman strutting its stuff.
Anole eggs found in a tomato pot. Photo by Karen Cusick.
The egg-laying habits of anoles are surprisingly little known. On Daffodil’s Photo Blog, Karen Cusick recently reported on the discovery of eight–count ’em, eight!–anole eggs in a tomato plant pot. Readers, where else have you found anole eggs?
Also, whose eggs are these? Both green and brown’s occur in Karen’s backyard. In Anolis Newsletter V, Todd Vincent provided tips on how to tell them apart.
Brown and green anole eggs. Photo by Todd Vincent.
And for some delightful footage on baby anoles, let’s not forget this old post.
If the biology of Anolis lizards is a puzzle, then a new paper by Yoel Stuart, Todd Campbell and colleagues is a crucial piece. It’s a puzzle piece that not only contains a wealth of information when held up on its own, but also brings clarity to a broader picture of anole biology when fitted into place.
Anolis carolinensis on small spoil-islands in Florida are the subject of Stuart et al. (2014)
A tight relationship between microhabitat and morphology characterizes variation across Anolis species in the Caribbean. Anole biologists have long suspected that negative interactions, such as competition, are responsible for driving different species into different microhabitats, with subsequent morphological adaptation to these microhabitats over evolutionary time. But pinning down interspecific interactions as the cause of evolutionary divergence in microhabitat and morphology has been difficult.
Why is establishing this causality challenging? Upon observing a pattern of consistent differences between populations of a species that occur in sympatry and allopatry with an interacting species, it seems logical to attribute this pattern to the presence of the interacting species. But many processes other than an evolutionary response to negative interspecific interactions can generate such a pattern–environments may differ between sympatric and allopatric populations in a way that drives the observed divergence, individuals from sympatric populations may all be similar only because they are closely related to each other, the divergence may be a consequence of phenotypic plasticity, or most dishearteningly, the whole pattern may simply be due to chance.
Ruling out these alternatives seems a gargantuan undertaking. Indeed, as Stuart and Losos (2013) point out, in a review that serves as a nice companion piece to this study, only a small fraction of studies describing patterns of divergence between sympatric and allopatric populations tackle the problem of eliminating these alternatives and can thus conclude with confidence that interspecific interactions cause the divergence they observe. But Stuart et al. (2014) take on the challenge.
Like recent research by Helmus et al. (2014) that exploits human-mediated anole dispersal to test classic principles of island biogeography, Stuart et al.’s (2014) research is rooted firmly in the Anthropocene. Occupying centrestage is the interaction between Anolis carolinensis, native to the United States, and Anolis sagrei, a relatively recent invader. The stage itself comprises small man-made spoil islands in Florida, created in the 1950s. When Todd Campbell began this study in the 1990s, A. carolinensis occurred on many of these little islands. Campbell introduced A. sagrei to three islands, and watched how, over the next three years, A. sagrei numbers rose steadily and A. carolinensis shifted higher into the trees on invaded islands, while continuing to perch at lower heights on nearby un-invaded islands.
Lead authors Yoel Stuart and Todd Campbell boating between spoil islands in FL
This rapid shift in microhabitat spurred Stuart and Campbell to return to the islands 15 years later (with a team of field assistants, of whom I was one!) to ask if A. carolinensis on invaded islands had subsequently diverged morphologically from conspecifics on un-invaded islands. By this time, A. sagrei had spread widely. Nevertheless, they found five un-invaded islands. A. carolinensis still perched lower on these un-invaded islands than on nearby invaded islands.
Across Caribbean anoles, species perching higher up on trees have larger toepads and more lamellae on these toepads than do species perching closer to the ground. Recapitulating this interspecific difference, Stuart et al. (2014) found that A. carolinensis on invaded islands had evolved larger toepads and more lamellae than lizards on un-invaded islands in about 20 generations, rapidly establishing a pattern of character displacement. But is this pattern caused by the presence of A. sagrei?
It seems almost criminal to squish into one paragraph everything that Stuart et al. (2014) did to rule out alternative explanations for the pattern of divergence. They reared hatchlings from invaded and un-invaded islands to rule out phenotypic plasticity as a cause for divergence, sequenced a mind-bogglingly large number of SNP loci to establish that A. carolinensis on invaded islands were not closely related to each other, and conducted intensive habitat surveys to rule out environmental differences between invaded and un-invaded islands. This mountain of work supports the idea that the presence of A. sagrei has driven the evolutionary divergence among sympatric and allopatric populations of A. carolinensis. It’s this mountain of work that makes Stuart et al. (2014) a tremendously satisfying paper. We now have a much firmer basis from which to suggest that interspecific interactions have driven patterns of ecomorphological diversification across Caribbean anoles.
But I personally think that this study’s most exciting implications arise from it defining more clearly a part of the anole biology puzzle that still remains relatively empty, namely our understanding of within-population, among-individual variation in microhabitat use and morphology, and the consequences of this variation for behavioural interactions. This summer I came across an A. carolinensis and A. sagrei perched together thus:
A. carolinensis perched below A. sagrei on the University of Florida campus in Gainesville.
These particular lizards couldn’t care less for Stuart et al.’s (2014) findings–clearly, the effect demonstrated in this study is a population-level effect. But this leaves us with a gap between behavioural interactions and eco-evolutionary dynamics–how exactly do we transition from individual A. carolinensis that are content to perch below A. sagrei to a population-level shift in A. carolinensis perch height in the presence of A. sagrei? Reassuringly, the divergence that Stuart et al. (2014) document is so rapid that this question becomes tractable–their results emphasize an opportunity to integrate behavioural timescale with eco-evolutionary timescales. We can now examine individual interspecific behavioural interactions among anoles, safe in the knowledge that ecological and evolutionary responses are not far behind.
Editor’s Note (October 28, 2014): Yoel Stuart provides the first perspon perspective on the study on eco-evolutionary dynamics
Editor’s Note II (November 3, 2014): The most thorough press coverage of this paper was in the Orlando Sentinel which as an added bonus had two animated talking anoles explaining the results.
Editor’s Note III (November 4, 2014): Yoel Stuart provides a more in-depth description of the study on the Howard Hughes Medical Institute’s The Conversation
In that classic of American cinema, Rocky III, Rocky Balboa (Sylvester Stallone) employed a particularly cunning strategy during the climactic fight with the younger, stronger Clubber Lang (Mr. T): he used his face to repeatedly absorb all of Clubber’s most powerful blows until Clubber grew very tired. Rocky’s strategy worked, and Clubber, fatigued from what seemed like hours of savagely beating Rocky in the head, ultimately succumbed to one of the relatively few punches Rocky managed to land.
Repeat until World Champion
Now one might suspect that Rocky III’s inspiring message of never giving up being punched in the face would have few adherents in the animal world, and this is indeed what we find. In most cases of male-male combat, combatants are reluctant to enter into escalated physical altercations because the risk of injury to themselves is too high. Instead, males of many animal species have evolved ritualized aggressive signals or displays aimed at intimidating their opponents into withdrawing, and will turn to violence only as a last resort when all else has failed. But some species have adopted the spirit of Rocky’s strategy, if not the letter, and rely on persistence to outlast as opposed to outfight their opponents.
A new study by Wilczynski et al. shows that Anolis carolinensis (the undisputed greatest study organism in the world) may use persistence as part of its fighting strategy as well. Adult male green anoles establish dominance hierarchies initially through aggressive interactions, and the outcomes of these interactions are affected by a variety of behavioural, physiological and morphological factors, many of which are likely reflected in the pattern and intensity of their ritualized aggressive displays. Wilczynski et al. set up staged aggressive interactions between pairs of adult males in the laboratory and tested whether males that responded faster or for longer to behavioural challenges were more likely to win fights. They also noted the colour state, as well as the presence of post-orbital eyespots, of winners and losers, both of which have been the subject of previous discussion on Anole Annals. 
The authors found that for the measured types of display, future dominant individuals generally displayed more frequently, and continued to display for longer than future subordinate individuals, whereas the effects of latency to display on competitive outcomes is less clear. With regard to colour, despite some intriguing trends, there were no significant differences between dominants and subordinates in any aspect of post-orbital eyespot expression. However, future dominant individuals did remain bright green for longer throughout the interactions than did future subordinates, supporting earlier suggestions that dark brown colouration is linked to subordinate social status and/or stress.
While persistence is a key component of contest behaviour in many animal species, the apparent importance of persistence in display duration in particular is especially interesting within the context of lizard displays. For example, duration of sagittal compression has previously been suggested as a handicap display in Uta stansburiana lizards, and previous studies have also suggested that persistence, perhaps related to accumulation of metabolic costs (paper here), might also dictate male contest outcomes in green anoles. Despite the wealth of knowledge regarding male green anole displays, studies such as Wilcynski et al.’s show that we still have much to learn regarding the behavioural aspects of male combat in this species, not to mention the likely relationships between behaviour and physiology.
Rocky III was unjustly spurned by the Academy of Motion Picture Arts and Sciences in 1983, not even receiving a nomination in the category of best picture (Ghandi won that year for some reason). Even more outrageous, it didn’t win the Best Original Song category it was nominated in! (Would anyone seriously argue that “Up Where We Belong” is a better song than “Eye of the Tiger”? Because it isn’t, and you are wrong). In retrospect, the reason for this travesty is clear: persistence is an important part of animal fighting strategies, and Rocky III was actually a nature documentary.
A recent paper by Matt Helmus, Luke Mahler, and Jonathan Losos highlighted the ways in which globalization has influenced the distribution of Caribbean Anolis lizards. At the heart of this research was the relationship between commercial shipping traffic and lizard biogeography. Two more recent observations can now extend these findings well beyond the Caribbean, much, much farther north.
First, Twitter user Vlen Puppehface recently posted a story about a stow away green anole that he found on pallet in Edmonton, Canada. This was a shipment of oil field supplies that originated in Houston, TX and that took ten days to reach its destination. This male green anole survived the trip all the way to Canada and is now housed in a new terrarium. The tweet originally posted October 16th and since then the anole has shed and appears to have adapted well to its new home.
The Canadien green anole.
Photo by Randi Duun
In separate case of stowaway lizards, another anole survived a transatlantic journey to Denmark in a shipment of bananas and was discovered incapacitated on the floor of the stockroom where incoming bananas are fumigated. The photo is too small for me to be certain, but this appears to be an Anolis cybotes female. According to the original post by Randi Duun in the “Anoles” Facebook group, the shipment originated in Colombia, Costa Rica, or the Dominican Republic so this would be consistent with an A. cybotes hitchhiker. It would be interesting to know how long a shipment like this takes, but I bet that it is longer than ten days port-to-port. Regardless, just like the globetrotting green anole, this anole is healthy following its journey, housed in a terrarium and enjoying Danish mealworms.
In contrast to the research described by Helmus et al, it is probably safe to assume that despite the perseverance of these anoles, and any others that make their way towards the arctic circle in subsequent shipments, escapees will not be establishing viable introduced populations.
Anolis phyllorhinus. Photo by Bret Whitney
Anolis dissimilis. Photo by Paulo Melo Sampaio
In a fascinating new paper, Ivan Prates and colleagues report on a phylogenetic analysis of Amazonian Dactyloa clade anoles with implications for a number of important topics in anole evolution.
The authors generated new mitochondrial and nuclear gene data for many Amazonian Dactyloa and combined those data with existing data from previous studies. Of particular note was inclusion of Anolis dissimilis, until recently known from only a single locality, and the Amazonian horned anole, Anolis phyllorhinus.
The paper had four main results, which I’ll go through seriatim. First, the overall phylogeny is very much in accord with Castañeda and de Queiroz’s previous work. The biggest difference is that A. dissimilis occurs in a distinct clade with A. neblinus and A. calimae. A relationship between the latter two species had been suggested by the previous work; A. dissimilis had not been included in those studies. The three species have quite disjunct geographic distributions (Amazonia, western Colombia, and the tepuis of the Guiana Shield, so finding them to comprise a distinct clade is interesting.
Anolis punctatus. You can almost see a horn ready to burst forth from the tip of that snout. Photo by Arthur Georges.
Second, as the figure below illustrates, A. phyllorhinus, as expected, groups with A. punctatus, whereas A. proboscis groups with the phenacosaurs (heterodermus group; though A. proboscis is not actually included in the analysis because genetic samples were not available; however, recent studies clearly indicate that A. proboscis belongs with this clade). Prates et al. note that, other than the horn, A. phyllorhinus and A. punctatus are morphologically very similar. I’ll take that one step further–you can almost imagine the antecedents of the horn as a swelling on the tip of the snout of A. punctatus. And, in addition, note that the horns of the two-horned species are very different-looking. Although Williams placed them in the species group, he did note that they actually didn’t look at that much alike. We now know that he was correct in this observation–hornedness is a convergent trait in anoles (no, I’m not calling it horniness).
Third, Prates et al. calculated divergence times, calibrated with three fossils that can be confidently placed in iguanian phylogeny.
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