SICB 2014: A Functional Approach to the Anole Dewlap

While we all know that the dewlap of Anolis lizards must provide some information about the signalling lizAnolis sagrei (male) 266ard to receiver lizards or predators, we remain uncertain about the exact nature of this information. By measuring aspects of dewlap design as well as myriad features of Anolis sagrei locomotor, immune, and behavioural performance, Tess Driessens of the University of Antwerp has begun to unravel the web of information conveyed by the dewlap.

Driessens’ results are complex, to say the least. Different features of the male dewlap relate in un-intuitive ways to various aspects of performance. For example, dewlap brightness was inversely proportional to jumping ability as well as immunocompetence, but directly proportional to haematocrit levels. Most surprisingly, given contrary results from previous work in A. carolinensis, size-corrected bite force in males was not related to any dewlap design variable in A. sagrei. In contrast to the male dewlap, no features of the female dewlap were found to relate to any measure of performance.

Though not unique to anoles, dewlaps are a defining feature of the genus, and I’ve always been amazed at how little we actually know about what dewlaps can say about the individual lizards that bear them. Driessens’ study is an important step towards answering that question.

 

SICB 2014: Suboptimal Locomotion in Anolis carolinensis

Cusick_FL_carolinensis_2 in grassA majority of biomechanical studies focus on eliciting maximal performance from animals in laboratory conditions, an approach that can make it difficult to apply results from the lab towards understanding performance in nature. Jerry Husak addressed this issue in his talk entitled “Maximal locomotor performance and sprint sensitivity in green anole lizards (Anolis carolinensis).”

By measuring sprint performance on a variety of perches (two different dowel widths, as well as a broad perch with pegs functioning as obstacles) and comparing these performances to sprint performance on a broad, flat surface, Husak showed that green anoles are substantially worse at running on narrow perches and through obstacles than at running on broad, flat surfaces. This confirms that animals moving through their natural habitats are almost certainly sprinting sub-maximally–in nature, green anoles are found most often on perches even narrower than those tested.

Crucially, the morphological correlates of performance varied by perch, suggesting that fine-scale studies of selection on limb and muscle morphology in the wild will require knowledge of how often and in what circumstances lizards navigate different microhabitats and move on different substrates. Coupled with behavioural observations in the wild, this study can pave the way for a more nuanced understanding of body shape evolution in our favourite lizards.

SICB 2014: Dynamic Energy Budget of Green Anoles

Quinn

A figure from Quinn’s poster, showing alternative possible energy budgets in green anoles (click for a better view).

Animals allocate energy that they acquire to a variety of bodily functions and activities. Some of the more important allocations are those toward metabolism and growth, though the relative allocations to these is unclear. McKenzie Quinn, an undergraduate student working with Michele Johnson at Trinity University, presented her work in the third poster session on the dynamic energy budget of green anole lizards. She quantified food intake, excretion, growth, and resting metabolic rate (RMR, the energy required for basic maintenance) of individual lizards over 40 days to create a predictive model to describe how they allocate energy. If metabolism receives a large allocation, then RMR and/or body mass are expected to be significant predictors of energy use. On the other hand, if growth is more important, then aspects of body length (snout-vent length, SVL) are expected to be better predictors.

Interestingly, she found that RMR and body mass were not included in the best model of energy use. Instead, their model building (with AIC criteria, if you’re interested) showed that a decreasing nonlinear function of SVL was the best model. This suggests that metabolic functions are a small, non-significant part of these lizards’ dynamic energy budget. This work was conducted on adult males, so it will of course be interesting to see how this approach might apply to younger individuals or females. However, this is useful information to know for those who wonder how anoles allocate energy in their daily lives.

SICB 2014: Regulation of Anole Limb Development

Readers of AA are very familiar with the dramatic differences in limb length among the anole ecomorphs, but we don’t yet know which genomic regions are involved in the evolution of anole limb length.  Carlos Infante, currently a postdoc in Doug Menke’s lab at the University of Georgia, presented a talk on his work to identify enhancers (short regions of DNA where proteins bind to enhance the transcription of a gene) that are associated with anole limb development.

Carlos first described a series of previous studies that did not find differences in the proteins expressed in the limbs of different anole species, suggesting that the differences in limb length are likely controlled by differences in gene regulation. However, examining a series of enhancer regions that were identified from previous work in mice also did not reveal differences in sequence variation that were correlated with limb length.

So, Carlos and his collaborators are using tools from the field of functional genomics to address this issue, using ChIP-Seq (a method that analyzes interactions between DNA and proteins) to identify active enhancers and promotors in embryonic Anolis carolinensis tissue using antibodies against Pitx1 (a transcription factor involved in hindlimb development) and H3K27ac (an acetylated histone mark).  By comparing results from these two datasets, they could identify enhancers that are expressed in forelimbs, hindlimbs, trunk tissues, or tubercles. Their plan for future work involves using the list they’ve generated of enhancers expressed in both forelimbs and hindlimbs to identify the regulatory regions that control the development of limb morphologies among Anolis species.

SICB 2014: Growth Hormone and Body Size in Anoles

GHIGF

A figure from Eric Mueller’s poster showing the conserved pathway of how growth hormone may affect body size.

Anyone familiar with Anolis lizards is aware of the dramatic variation in body size. Think dwarf twig anole and crown giant. Although the ecological and evolutionary processes that can lead to such variation in body size have been studied, it is still unknown what physiological mechanism explains the variation we see today. Eric Mueller, a graduate student at Southern Illinois University – Edwardsville, presented a poster asking just that question. Specifically, do differences in circulating levels of plasma growth hormone regulate evolutionary changes in body size among anole species of differing size and morphology?

Untitled

Anolis carolinensis (L) and A. equestris (R) have dramatic differences in body size but not in growth hormone levels. (photo 1, 2) Species not to scale.

Growth hormone (GH) is secreted by the pituitary gland and has many functions in the body, including promoting muscle and bone growth and increasing protein synthesis (among many, many other things!). It seems a logical candidate mechanism to investigate when it comes to explaining variation in body size. Mueller looked at GH levels in three anoles of varying size:  A. equestris, A. carolinensis, and A. sagrei. GH was higher in A. equestris and A. carolinensis than A. sagrei, supporting his hypothesis. However, there was no difference in GH levels between A. equestris and A. carolinensis despite dramatic differences in adult body size. Looking within species, GH levels were positively correlated with SVL only in A. equestris, and not the other two species.

Although differences in circulating GH may explain some size differences among anole species, as in other studies of anole hormones, things don’t seem to be simple. Mueller hypothesized that other aspects of the GH pathway may be more important. For example, GH receptors, Insulin-like Growth Factor (IGF) levels, and IGF-binding proteins should be examined for a full picture. The GH-IGF axis also interacts with other hormone pathways, such as testosterone, making this a very complex issue. Since endocrine systems are so multi-faceted, and multiple components have the possibility to evolve independently, there is lots of potential for future research that seeks to explain species differences in body size.

 

SICB 2014: Micro-landscape Variation in Reproduction

It was a real pleasure to see Dr. Ray Huey give a presentation that was inspired by research he and his collaborators began in the 1970s on seasonality of reproduction and behavioral thermoregulation in Puerto Rican Anolis cristatellus. Almost 40 years after the publication of that work, Huey and many of the same colleagues (and some new ones) returned to the same areas in Puerto Rico to examine how very fine-scale variation in thermal environment (a few meters!) might lead to variation in reproduction. The investigators (Otero, Huey, and Gorman) studied how reproduction differed between open areas (where lizards carefully thermoregulate) and forested areas (where lizards are thermoconformers) and found striking differences between them. Females in open habitats reproduced most of the year, whereas females in the neighboring forest decreased reproductive in a much more seasonal manner. Differences were largest from October – December, with females in forested habitats essentially shutting down reproduction during those months. This finding was true at two different sites.

These striking differences in reproductive phenology are similar in magnitude to differences seen along elevational gradients, but the difference here is the scale. The females that Huey compared were literally only a few meters away from each other. One important take-home message from these data is that reproduction can vary at the microgeographic scale just as it can at larger geographic scales. While the latter type of study is now common, the former isn’t. Future work should consider how small-scale variation in microhabitat use might influence reproduction so that we can better understand how general this phenomenon is.

One final point that Huey made was how collaborations can not only be an integral part of research, but also a source of personal reward as those collaborations continue over time and result in great friendships. He encouraged young investigators to keep this in mind as they progress through their academic careers.

Editor’s note: this research project has been the subject of previous posts [1,2].

SICB 2014: Arginine Vasotocin and Social Behavior

800px-Vasotocin 800px-Anolis_carolinensis_mating Arginine vasotocin, the reptilian homolog to vasopressin is a potent modulator of social behavior. (photos from Wikipedia)

For many of us, hearing about arginine vasotocin (AVT), or its mammalian homolog vasopressin, conjures up memories from a physiology class about water balance and the antidiuretic effects of the vasopressin system. However, AVT is also a potent neuromodulator and neurotransmitter in the brain that has strong effects on social behavior, such as parental care and pair bonding. Although most of this behavioral research has been done in mammals and birds, it appears that AVT might have similar behavioral functions in anoles! Leslie Dunham, a graduate student at Georgia State University, experimentally assessed the effects of AVT on male and female green anole behavior. By comparing lizards injected with either AVT or a control solution, Dunham was able to examine the effects of AVT on aggression and courtship in males. The behavior of individuals in the two experimental groups was then assessed in the following contexts: aggression toward a mirror, aggression toward another male, and courtship toward a female. She found:

  1. Decreased aggression toward a mirror.
  2. No difference in aggression toward a size-matched male.
  3. No difference in courtship behavior directed at a female.

AVT decreases aggression in other vertebrates, but the lack of an effect on courtship in anoles suggests that AVT may modulate behavior differently in male anoles compared to fish and birds.

But wait, there’s more! Not to be outdone by other types of vertebrates, females in the courtship trials showed some very interesting behavior. Although Dunham focused on the effects of AVT on male behavior, she also measured female behavior during the trials. She found that females displayed more toward males treated with AVT compared to control males. This was despite any detectable behavioral difference between the male treatment groups. Why is this? Although the answer is still unknown, Dunham proposed some plausible and testable hypotheses for what might be happening. First, there may be subtle changes in behavior brought about by AVT that weren’t detected. Second, there may be a role for chemical communication between the sexes during courtship that wasn’t measured. Anoles, and iguanian lizards in general, aren’t known for their reliance on chemical communication, so this possibility is sure to spark some interesting future research.

SICB 2014: Why Curly-Tailed Lizards Curl Their Tails

Continuing with my theme of posting about non-anoles that anolologists find interesting, here’s a summary of a fascinating poster about tail-curling in two species of LeiocephalusL. carinatus (the famous consumer of A. sagrei in the Bahamas) and L. barahonensis. Tail-curling is known to function as a predator-deterrent signal in L. carinatus, but its potential as a social signal has remained unexplored. Bonnie Kircher, a student in Michele Johnson’s lab at Trinity University, set about rectifying this gap.

Having never seen a curly-tail myself, I was surprised to learn that these lizards exhibit a variety of tail-curling behaviours.

A figure from Bonnie Kircher's poster describing how tail-curling was scored in this study.

A figure from Bonnie Kircher’s poster describing how tail-curling was scored in this study.

By scoring the intensity of tail-curling during social encounters as well as during non-social periods, Kircher showed that tail-curling was not used as a social signal in either Leiocephalus species. In an elegant control, she demonstrated that head-bobbing was more frequent in social than in non-social contexts, thus verifying that social contexts were indeed accurately identified.

Kircher also simulated predation by approaching the lizards and observed their use of tail-curling while fleeing. A comparison of the frequency of tail-curling between disturbed and undisturbed lizards confirmed that L. carinatus uses tail-curling as a signal during encounters with potential predators. The same pattern was not observed in L. barahonensis–we therefore don’t yet know why this species curls its tail. Kircher speculates that the behaviour might have been directed at other, undetected, predators, or perhaps plays a role in lending stability to the lizard during locomotion.

This variation in the utilization of the same signal between two closely-related species points to the lability of signal use, and with almost 30 species in the genus, this system is a prime candidate for future work on signal evolution.

SICB 2014: Hemiclitoris Development in Anolis distichus

Anoles display a staggering amount of phenotypic diversity, even in their genital morphology. Traditionally research has focused on characterizing the diversity and function of male genitals, or hemipenes, but females also possess paired genitals, or hemiclitorises, and yet almost nothing is known about them. In fact, female genital morphology is poorly understood across all reptiles. To date, we know that in some species hemiclitorises appear as miniaturized versions of hemipenes, whereas in other species they are unique structures. Further, the timing of sexual differentiation of genital structures appear to differ among lizard clades. Clearly, we need a broader understanding of the form, function, and evolution of female genitalia in reptiles.

In a fascinating poster, Casey Gilman, a graduate student at the University of Massachusetts, Amherst, presented her work on the development and morphology of hemiclitorises in the bark anole, Anolis distichus. Here’s the abstract:

Genitalia are extraordinarily diverse and show remarkably rapid evolution, relative to other morphological traits, across a wide range of animal taxa. Male and female genitalia in many animal groups begin as the same embryonic structures and later go through hormone-mediated differentiation. Surprisingly, little is known about the genetic mechanics of these processes. Even less is known about external genitalia differentiation in reptiles. Unlike other amniote groups, lizards and snakes possess a set of paired reproductive intromittent organs, called hemipenes. In a number of lizard species, females retain miniaturized versions of the male genitalia, called hemiclitorises. In these species, hemiclitorises can be used for taxonomic purposes, as they retain many morphological characteristics of the male genitalia, which are often species-specific. In lizards, the external genitalia of both sexes grow at the same rate until approximately halfway through embryonic development. Following this period, the hemipenes of the males continue to grow while the hemiclitorises of the females regress until they are about half the length of their male counterparts. We investigated the development of male and female external genitalia in Anolis distichus to determine the timing and patterning of growth and regression of these structures using histology, immunohistochemistry and whole mount in situ hybridization.

SICB 2014: Novel Insights into the Evolution of Cold Tolerance

 

Green anole eating a dronefly. Photo from Wikipedia.

 

The tremendous diversity in Anolis lizards is one of the major draws for researchers to work on this system. There are nearly 400 species of anoles and their distribution spans much of the New World. Most of Anolis’ distribution spans environments with very low seaonsality. One exception is Anolis carolinensis, whose range spans much of continental North America, and encompasses highly seasonal environments. Further, unlike most reptiles, A. carolinensis does not hibernate during the winter. Rather, lizards remain active during the cold North American winter months.

Today Shane Campbell-Staton, a graduate student at Harvard University, presented some of his thesis work examining how A. carolinensis adapts to the thermal environment, and how local adaptation influences patterns of gene flow. The work he presented was conducted in collaboration with Scott Edwards and Jonathan Losos at Harvard University and Zachary Cheviron and Anna Bare from the University of Illinois-Urbana Champaign.

Shane first asked whether differences in the thermal environment limit gene flow among populations of A. carolinensis. To answer this question, he examined variation in over 2000 loci for 131 individuals of A. carolinensis and its ancestor, A. porcatus, from Cuba. He leveraged the Anolis genome with double digest RADseq to discover these SNPs and used multiple matrix regression to assess the correlation between genetic distance among populations and geographic and climatic distance. He discovered a significant signal of isolation by temperature, but not isolation by geographic distance or isolation by precipation. This means that populations are likely structured by thermal habitat, and that differences in temperature among localities limit gene flow in A. carolinensis.

Next Shane asked whether there was a signal of local adaptation in physiological tolerance to the thermal environment. He measured heat tolerance (CTmax) and cold tolerance (CTmin) in nearly 200 individuals of Anolis carolinensis. He found a significant positive correlation between temperature seasonality and thermal tolerance (i.e., the difference between CTmin and CTmax), but that most (though not all) of this pattern was driven by variation in cold tolerance across habitats.

Finally, Shane wanted to understand the mechanism that limits cold tolerance for terrestrial ectotherms. Specifically, he wanted to test whether oxygen limitation plays a role in determining how cold tolerant lizards are. The oxygen limitation hypothesis suggests that the ability to transport and utilize oxygen is limited at cold temperatures, and that lizards lose their mobility at low temperatures because they can no longer effectively transport oxygen to their muscles. Under this scenario, lizards that are more tolerant cold should be more efficient at transporting oxygen at cold temperatures than less cold tolerant individuals. To test this hypothesis, he examined CTmin in lizards from different thermal extremes of the species range and found that lizards from more cold-tolerant populations (i.e.,: higher latitude) utilized less oxygen at colder temperatures. His results support the oxygen-limitation hypothesis, and suggest that lizards can achieve a greater tolerance to cold, at least in part, by becoming more efficient at transporting oxygen, thereby reducing their demand for oxygen at lower temperatures.

SICB 2014: Neural Correlates of Communication Modalities in Lizards

 

The six species examined by Robinson and colleagues.

The six species examined by Robinson and colleagues.

Reptiles differ vastly in how they communicate. Some species are predominantly visually-oriented, whereas other species rely almost exclusively on chemical signals for communication. Despite such marked differences in communication modalities, there is surprisingly little known about how communication modalities translate into differences in neuranatomy among species. Chris Robinson, an undergraduate working with Dr. Michele Johnson at Trinity University, presented a study examining the relationship between sense perception and neural density in six species of lizards.

Chris predicted that visually oriented lizards should have larger and more densely packed neurons in two visual centers – the lateral geniculate nucleus (LGN) and the optic tectum (OT) – whereas lizards that employ chemical modalities should have a similar pattern in the nucleus sphericus of the amygdala (NS). He included three iguanid species in this study, the green anole Anolis carolinensis, the curly tail Leiocephalus carinatus, the Texas spiny lizard Sceloporus olivaceous, as well as the whiptail Aspidoscelis gularis, the skink Scincella lateralis, and the Mediterranean house gecko Hemidactylus turcicus. To determine which sensory modalities best characterized each species he performed focal behavioral observations. During these observations, he quantified the number of chemosensory behaviors (rubbing the cloaca on a substrate, licking the air or substrate) and visual behaviors (head bobbing, dewlapping, and tail curling). Chris amassed over 120 hours of behavioral observations, and 10-33 hours per species, which is no small feat.

Continue reading SICB 2014: Neural Correlates of Communication Modalities in Lizards

SICB 2014: The Ecomorphology of (Some) Australian Geckos

Though SICB 2014 is positively teeming with cool anole talks and posters, there are plenty of other lizards that are getting a lot of attention. Yesterday, I happened upon a fascinating talk by Travis Hagey,  a grad student at the University of Idaho, titled “How geckos stick in nature: ecology and biomechanics of gecko feet.”

Strophurus taenicauda, a grass-bush-like gecko. Photo by Dave Fleming.

Strophurus taenicauda, a grass-bush-like gecko. Photo by Dave Fleming.

Addressing an overflowing room, Hagey used the dramatic diversity of gecko toepads to motivate his central question–can this diversity in toepad morphology be explained by the habitat preferences and perch-use behaviour of these geckos in nature? But going down the path of ecomorphology led to a comparison with anoles: if gecko toepads correlate with their habitat, then what about gecko limb-lengths? Using relationships between limb morphology and perch-type from arboreal anoles as well as rock-dwelling skinks, Hagey left for Queensland, Australia, with three predictions:

1. Geckos with shorter limbs would perch on narrower surfaces

2. Geckos with longer limbs would perch on rocks

3. Geckos with higher clinging ability would perch on steeper perches.

Utilizing a simple measure of lizard clinging ability (the “toe detachment angle,” which is the angle of the clinging surface away from vertical at which a lizard can no longer cling), as well as measuring perch characteristics and limb morphology for 13 species of geckos, Hagey began to look at patterns of ecomorphology. He found that different species occupied dramatically different habitats, with specialization even within the arboreal niche. Here’s what he found for each prediction:

1. Contrary to expectations, lizards perching on narrower surfaces had relatively longer limbs than average.

2. Having longer upper legs, however, correlated with rock use.

3. A higher clinging ability was correlated with having longer toes and shorter limbs. There was a qualitative or clade-specific relationship between the use of vertical perches and higher clinging ability.

Pseudothecadactylus australis, a crown-giant-like gecko. Photo from www.gondwanareptileproductions.com

Pseudothecadactylus australis, a crown-giant-like gecko. Photo from www.gondwanareptileproductions.com

Hagey speculated about the relationship between perch width and limb length in geckos, where he found the opposite pattern from anoles. One distinct possibility is that geckos have, on average, shorter limbs than anoles, meaning that a relatively long-limbed gecko and a relatively short-limbed anole may actually have the same body shape. Hagey is planning a taxonomically broad comparison of body shape and perch use, and hopes to include both geckos and anoles in this dataset–an exciting prospect that could shed light on some remarkable trans-continental convergences in lizard ecomorphology.

SICB 2014: Invasive Lizards Are ‘Bolder’ than Native Lizards

The anole species examined by Davis and Johnson

The anole species examined by Davis and Johnson

The annual meeting for the Society for Integrative and Comparative Biology (SICB) has kicked off and anoles are off to a roaring start. At the first poster session of the conference this afternoon, Lauren Davis, an undergraduate student working with Dr. Michele Johnson at Trinity University, will present her work on the behavioral and neural correlates of invasive ability in anoles (poster 1.19). Davis wanted to know whether invasive anoles can be identified by specific behavioral syndromes, or suite of behaviors that are expressed across different contexts. Specifically, she wanted to know whether invasive lizards are ‘bolder’ than native lizards and, in turn, invasive lizards have larger or denser neurons in neural regions associated with boldness (i.e., the amygdala, hippocampus, and hypothalamus).

To address these questions Lauren focused on three species of anole that vary in ‘invasiveness.’ These were Anolis carolinensis, a native species, A. distichus, a ‘semi-invasive’ species, and A. sagrei, a highly invasive species. She hypothesized that more invasive anoles should be ‘bolder’, meaning that they exhibit a propensity to explore novel environments, exhibit more aggressive behavior, possess higher overall activity levels, and have more behavioral flexibility (defined below) than native range lizards.

Continue reading SICB 2014: Invasive Lizards Are ‘Bolder’ than Native Lizards

Quest for Anolis roosevelti

This is not Anolis roosevelti. No pictures of that species in life exist. But it probably looked pretty similar to this brown-phase Anolis cuvieri. Photo by Alejandro Sanchez.

Anolis roosevelti, the giant anole of Culebra and Vieques, is famous in anole circles. The only Caribbean species thought to possibly be extinct, the species has not been seen since 1932.

Recently I learned of a report of an expedition to Culebra to track down the wily saurian, written by noted author and mycologist Lawrence Millman. As you’ll see, the expedition was a success, but perhaps not in the way you expect.

A Hunt for the T. rex of Anole Lizards: A Trip to Puerto Rico in Search of a Giant Shrinking Reptile.

Christian Science Monitor, July 12, 2007

“Not too long ago I picked up an old travel book about Puerto Rico and read of a rare giant lizard, Anolis roosevelti, on the island of Culebra.
“Fame will visit anyone who finds this elusive creature,” the author of the book proclaimed. Since Fame had thus far given me a rather wide berth, I hopped a plane to San Juan and then a smaller plane to Culebra.
By the time I arrived on the island, the lizard had shrunk. The book had described it as four feet long, but the local Fish and Wildlife person told me that it was no more than a foot long from snout to vent – hardly competition for a T. rex. Still, A. roosevelti is a T. rex compared with other anoles, which are among the smallest of all lizards.
I also learned that this giant among anoles had not been sighted since 1932. Not officially sighted, that is. But there were anecdotal reports of it being seen in the forested areas on Monte Resaca, Culebra’s highest summit (height: 650 feet), as recently as a few years ago.
So I drove to the base of Monte Resaca and started bushwhacking.
Trusting in serendipity, I expected to see the anole in question basking on every boulder as well as ascending every gumbo-limbo tree. I was so intent on my search that I lost all sense of direction and ended up in someone’s backyard.
A Culebran tending his garden looked up at me in surprise. My usual ploy when I trespass like this is to advance confidently toward the person, shake his hand, and announce in a punctilious English accent: “Dr. Basil Withers of the British Antarctic Survey. Jolly good to meet you, old chap.”
Since this ploy would not work in the subtropics, I said, “Hello, Señor. Seen any big lagartos around here lately?”
“Sí,” the man replied. “All the time.”
“What’s their habitat?” I asked excitedly.
“In my bathroom,” he answered. He invited me in, where I saw the lagartos skittering around on the wall. They were geckos, not anoles, and they weren’t even all that big.
Serendipity had gotten me nowhere, so I got in touch with Beverly Macintyre, who knew the island’s backcountry intimately. She mentioned a particular boulder canyon on Monte Resaca, just the sort of place, she said, where a giant anole might hang out. Then she referred to recent development on Culebra; if it continued at its current breakneck pace, she said, a lot more creatures than A. roosevelti would be either endangered or extinct.
In our search for the lizard, Beverly and I entered not so much the forest primeval as the forest prickly. Ground-hugging cacti jabbed us, mesquite bushes stabbed us, saw-toothed bromeliads slashed at us, and a plant known locally as Fire Man (Tragia volubilis) delivered stings that make the stings of a stinging nettle seem positively genteel.
And to add to it, at one point I was gazing up at what turned out to be a green tree iguana and walked into a barbed wire fence.
We did not see a giant anole. We did not even see one of the small anoles that reputedly were common on the island. But near the end of our trek, we did witness this unusual sight: a man on a horse with reins in one hand and a cellphone in the other.
The next morning, as I took a respite from my search, I began noticing other curious sights. A sign in a shop window in Dewey, the island’s only town, said: “Open Some Days, Closed Others.” A road sign indicated Termina Carretera (End of Road) when, in fact, the road did not end at all.
And in the afternoon, I was sitting on Flamenco Beach when a person in an old-fashioned diving bell emerged from the sea. At the north end of the beach, there was a tank left over from the days when the US Navy used Culebra for war games; in this setting, it had a very surreal quality.
I began to think that I had fetched up on some sort of Caribbean fantasy island – an ideal habitat for, among other things, an incredible shrinking lizard.
Several days later, I still hadn’t found the anole in question. My trip was coming to an end, so I asked Teresa Tallevast, the manager of the Culebra National Wildlife Refuge, if there was any area I might have overlooked. She suggested that I check out the trail that wound down from Monte Resaca to Playa Resaca.
Soon I was hiking on this steep trail. Every once in a while I would stop and peer into the surrounding bush. At one point I thought I saw a finned reptilian tail disappear into a tangle of mesquite, but that could have been my imagination … or another iguana.
At the bottom, the trail meandered through a labyrinth of white mangroves. I looked up at the trees’ gnarled branches and then down at their arching prop roots.
Still no anole.
At last I came out on Playa Resaca, a long, yellow swath of sand where I was the only person in sight. The sun was blisteringly hot, but I didn’t go for a swim. Resaca means undertow in Spanish, and if I had gone swimming, I might have washed ashore on the west coast of Africa or, at the very least, in the Virgin Islands.
Suddenly I saw what appeared to be the tread marks of an 18-wheeler in the sand. I was outraged. But then I realized that the tread marks were actually the flipper imprints of a female leatherback turtle who’d plodded ashore the night before to lay her eggs. Weighing a thousand pounds or more, such creatures are the reptilian equivalent of giant rigs; unlike those rigs, however, leatherbacks are an endangered species. I counted myself extremely fortunate to see even the tracks of one.
And so it was that my quest for a rare reptile on Culebra ended in success.”

Ellee "hugging the tree" while Michele chased the lizard.  Photo by Thom Sanger.

Dewlap Color May Indicate Parasite Load, or Anole Biologists Should Hug More Trees!

This post was written by Ellee Cook, a current graduate student at Duke, and a former undergraduate in my and Troy Murphy’s labs at Trinity University.

Dewlap displays are arguably the most striking characteristics of Anolis lizards. In many anoles, we observe variation in dewlap color and display among members of the same species, and in some cases, among members of the same population. However, we do not fully understand what influences this variation, or if variation in these traits has implications for anole communication. Recent work by Julienne Ng and colleagues with A. distichus (reviewed in a post by Jonathan Losos) suggests that genetic factors are determinant of dewlap variation. But, it is unclear whether dewlap characteristics or display behavior vary in accordance with lizard condition, or whether these traits are affected by parasites.

In our paper published earlier this year, we investigated the potential for individual variation in dewlap color and display behavior to serve as honest indicators of ectoparasitic mite load in Anolis brevirostris, a trunk anole from southwestern Dominican Republic that’s closely related to A. distichus. Male A. brevirostris exhibit extraordinary variation in dewlap coloration and have dewlaps that range from yellow to red-orange. Lizards in our study population were naturally parasitized by trombiculid mites.

Ornamental coloration and display behaviors are often negatively affected by parasites. This trade-off occurs because the resources required to produce ornaments often also function in important physiological processes, such as the carotenoid pigments responsible for red-orange ornamental coloration in many organisms that may also act in immune function as free-radical scavengers. Parasitized individuals divert resources to battling infestation, rather than to maintaining ornamentation. Thus, ornament quality can serve as an honest indicator of advertiser quality—might dewlap variation indicate anole parasite load?

We observed the display behavior of male A. brevirostris and then attempted to capture observed individuals to quantify ectoparasite load, body condition, and dewlap coloration. However, we quickly learned that these lizards are easy to see, but fast and tricky to catch. Although they can be noosed, they usually run high into the canopy, where they become difficult to see and nigh uncatchable.

After several frustrating failed captures, we implemented a 2-person “hug-the-tree” method (suggested by the illustrious Thom Sanger) to snag the individuals for this study.  When the lizard was just a few feet above the ground, one of us would quickly throw our arms around the tree just above the lizard, effectively “hugging” the tree. Because A. brevirostris tend to run up rather than down onto the ground, hugging the tree contained the lizard in just a few feet of tree trunk, wherein a second person can catch the lizard by hand or noose. Although there were some long games of “chase-the-lizard-around-the-tree,” hugging the tree ultimately proved very effective for catching A. brevirostris and other anoles with similar habits.  We mastered this method and proceeded to perform focal behavioral observations and capture 30 adult male A. brevirostris. We then counted ectoparasitic mites and estimated body condition using SVL and mass. We used an objective spectrometer to quantify dewlap brightness, hue, and saturation.

We found that heavily parasitized males exhibited duller dewlaps, performed fewer dewlap extensions, and had lower body condition than males with fewer parasites. This suggests that trombiculid mites may be negatively affecting the condition of these lizards, and that individual variation in dewlap color and display behavior may indicate parasite load. These results are intriguing, given that they indicate that variation in ornamental color and display may convey information about advertiser condition.

Jamaica: A Land of Imperiled Nature: Threats to Jamaica’s Coastal Ecosystems Due to Proposed Development of the Goat Islands

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Anolis grahami in the Hellshire Hills

Today, the genus Anolis represents the most common of Jamaica’s reptiles. Indeed, most Jamaican anoles are quite ubiquitous throughout the island, but the abundance of these and other small lizards  is misleading. Many of Jamaica’s reptiles, several of which are endemic to the island, are in immediate danger of extinction. Indeed the Jamaican herpetofauna is one of the most threatened in the entire Caribbean and several species have already been lost; Many more are now under threat under threat due to  development in Jamaica’s  protected habitats.

Map showing the major protected areas and nature reserves of Jamaica including the Portland Bight Protected Area, inclusive of the Goat Islands source:http://inweh.unu.edu/jamaica-mpa/

Map showing the major protected areas and  reserves of Jamaica
source: http://inweh.unu.edu/jamaica-mpa/

Over the years  numerous protected areas have been established across Jamaica  with the intent of preserving its endemic biodiversity, particularly birds, mammals and reptiles. Two of these areas, the Black River Morass and Portland Bight Protected Area,  are significant refuges for a large number of Jamaica’s threatened endemic reptiles.

 

 

Juvenile American crocodile Crocodylus acutus

Juvenile American crocodile.Crocodylus acutus. A large population of this threatened species currently inhabits the Black River Morass
Crocodylus acutus. Photo by author

By far the most important nature reserve in Jamaica is the Portland Bight Protected Area (PBPA) created by the Jamaican government in 1999. It is the largest protected area in Jamaica and spans approximately 1,880 square kilometers of wetlands, coastal mangroves and coastal dry forests, all three of which are important threatened ecosystems. Although the first priority in forming the protected area was to protect the coral reefs found within, it also serves to protect vulnerable and endemic species. The PBPA encompasses the Hellshire Hills and Portland ridge in the parishes of St. Catherine  and Clarendon respectively; these are the two largest areas of dry forests remaining on Jamaica and form one of the largest areas of relatively intact tropical limestone forests in entire Caribbean.

The coastal dry forests of the Hellshire Hills, part of the Portland Bight Protected Area source:http://www.flickr.com/photos/cyclura/3267735122/

The coastal dry forests of the Hellshire Hills, part of the Portland Bight Protected Area.
Source: Joe Burgess’s Flickr page

The PBPA  is a reserve for several threatened species of plants and animals and serves as the last refuge for several of Jamaica’s rarest reptiles including the Jamaican iguana, Cyclura collei, which with a global population of 150 lizards is one of the rarest reptiles in the world. The area is also home to the Jamaican skink,  Mabuya fulgida, and the small recently rediscovered blue-tailed galliwasp, Celestus duquesneyi,  both of which have extremely limited distributions outside of the Hellshire Hills, as well as the endangered Jamaican  boa, Chilabothrus subflavus,  which is patchily distributed throughout the Island. The PBPA also encompasses several offshore cays including Little Goat island and Great Goat Island; The  Jamaican government had plans to eradicate the mongoose as well as the feral goats from the Goat islands after which suitable organisms from the mainland dry forests would be transplanted onto the islands in an effort to preserve the endemic dry forest biodiversity. This plan however seems to have hit a a monumental roadblock. Continue reading Jamaica: A Land of Imperiled Nature: Threats to Jamaica’s Coastal Ecosystems Due to Proposed Development of the Goat Islands

Ameiva

Ameiva ameiva

Ameiva ameiva Photo from Fagner Delfim’s Flickr page

Here at Anole Annals we like to obsess over our  favorite lizards, anoles of course, but there are a vast array of other reptilian marvels out there,  formidable  Cyclurid iguanas, regally patterned Chilabothrus boas and of course the ever wary ground lizards of the Antilles (and elsewhere), the ameivas. Given the ample opportunity for exploration of these seemingly under appreciated animals  I have taken my best shot at writing a post concerning ameivas,  their morphology, ecology an various other bits and pieces of info I’ve picked up over the years; Enjoy!

The large neotropical genus Ameiva contains roughly thirty-two species largely distributed throughout eastern South America and the Caribbean with a few species  extending into southern Central America. Within this genus are some of the  most ubiquitous lizards of the neotropics, though due to their incredible swiftness and skittish demeanor it is rare that one ever sees one of these charismatic lizards out in the open for any extended period of time and even rarer that the casual observer  may encounter enough of them within a single area to appreciate just how numerous they can be. This rather ambitious  post focuses mainly on the  biogeography of  Ameiva, which in many ways mirrors that of Anolis. Most of the information presented herein comes from a 2012 paper  which , among other things, revises the genus Ameiva, recognizing several monophyletic clades and excluding certain species once thought to belong to the genus. More info on ameivas, as well as some amazing pictures, can be found at Father Alejandro Sanchez’s website.

Four geographically coherent clades or species groups have been identified within Ameiva,  two of which, the ameiva and bifrontata groups, occur in South and Central America as well as in Trinidad and Grenada, while the remaining two, the dorsalis and erythrocephala groups,  are distributed parapatrically throughout the Caribbean. Two additional species, A. parecis and A. concolor remain unassigned to any of these four groups.

The bifrontata group is the smallest of the four clades, consisting of one polytypic  species, A. bifrontata, as well as the closely related A. provitaae.

 This group is almost entirely South American in distribution, occurring in Colombia and Venezuela as well as on the island of Aruba. The clade is thought to share common ancestry with the West Indian  Ameiva species and both groups share several defining morphological characteristics the most obvious of which is the presence of mild to intense red coloration on the tip of the snout of most species, a feature shared by no other teiids.

The Caribbean  Ameiva form a monophyletic clade thought to be of South American origin
with the South American  A. bifrontata  species group thought to be sister  this one. Continue reading Ameiva