Category: New Research Page 33 of 66

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.

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

By Martha Muñoz

On January 4, 2014

In Introduced Anoles, New Research

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.

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

By mjohnson216

On January 2, 2014

In New Research

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.

The Role Of Genes And Diet In Determining Dewlap Color

By Jonathan Losos

On December 13, 2013

In New Research

Results of mating trials in Ng et al.’s study. Top two rows are within-population crosses; bottom two are between crosses from different populations that differed in dewlap color. Note that in the top, individuals look like their fathers, whether at the bottom, dewlap colors are intermediate between that of the two populations.

Everybody loves a pretty dewlap, and recent years have seen a lot of interest in studying the factors that determine dewlap color, as well as the role dewlap color may play in species recognition, sexual selection and other processes. Many have suggested that the dewlap is a focus of sexual selection; some have even opined that it is an honest signal of something, maybe good genetic quality, maybe the ability to procure lots of color-inducing dietary items. Unfortunately, we know almost nothing about the genetic basis of dewlap color, nor about the effect of environmental variation.

Anolis distichus exhibits more variation in dewlap color and pattern than any other anole, and thus is the perfect choice for such a study. Julienne Ng just completed her doctoral research at U. Rochester on this species, documenting that variation in dewlap color correlates with environment among populations. Now she and colleagues report on laboratory studies to assess the extent to which variation is determined by genes vs. diet.

Why diet? Because reds and oranges are likely determined by carotenoids, which vertebrates cannot synthesize. Thus, it is plausible that the amount of carotenoids ingested by a lizard may correlate with its color. This hypothesis has only been tested once before, in a study on A. sagrei by Steffen, who failed to find evidence for a diet effect on the red-orange dewlap of this species.

This study had two components. First, to study genetics, lizards from two populations–one with an orange dewlap, the other with a plain whitish dewlap–were crossed in the laboratory. Second, lizards were fed lots of carotenoids.

The results: strong evidence for a genetic basis for variation in dewlap color. Purebred individuals looked like their fathers (top two rows in figure above), but crosses were intermediate in color (bottom two). Pretty strong evidence for a genetic basis for the trait. And the effect of diet? Not so much. No difference in color between lizards in the carotenoid supplementation treatment vs. the control lizards.

The bottom line is that, at least in this species, genes control variation in dewlap color. Combined with Steffen’s study, there are now two negative results for a role of diet. Of course, work on other species is necessary to confirm the generality of these results, as well as additional investigation into the exact genes responsible for dewlap color.

Tail Loss and Locomotor Performance

By Eric McElroy

On December 10, 2013

In New Research

The long-tailed Asian lacertid lizard, Takydromus sexlineatus. Photo by John White.

Tail loss (aututomy) is one of the more amazing things done by lizards, but for for me it’s a frustrating reality of studying the physiology of sprinting because rough handling (by me when I was a beginning Ph.D. student and now in my lab by some undergrads) results in a lost tail and thus changed locomotor mechanics. But this frustration turned to fascination when I began studying locomotion in Takydromus sexlineatus. This species is pretty special as it holds the distinction of having the longest tail (relative to snout-vent length) of any lizard.

So I had to pull the tail off and measure how locomotion was changed. This then snowballed into studying the effect of autotomy in Anolis carolinensis and then a collaboration with Philip Bergmann to more broadly address how autotomy influences locomotor performance in lizards by using a meta-analysis of the published literature. We showed that longer tails result in a more drastic change in performance for all lizards studied except the two Takydromus species…so we are still left wondering what that huge tail does!

The result was a talk at the World Congress of Herpetology in Vancouver and a publication in Physiological and Biochemical Zoology as part of a special issue on Tail Loss in Lizards, organized by Tim Higham and Tony Russell.

Grass anoles have really really long tails too….I wonder how those tails are used? Convergence between Takydromus and Grass Anoles? E.N. Arnold did a lot of work on Takydromus and hypothesized that the tail aids in grass-swimming. I have observed this species stand up bipedally and use the tail as a prop (like Varanus). Thoughts?

New Paper on the Little Known Large Mexican Anolis macrinii

By Jonathan Losos

On December 9, 2013

In New Research

Almost nothing is known about Anolis macrinii, which is a little surprising because it is rather large (nearly 100 mm snout-vent length) and apparently locally moderately abundant. However, it’s small, localized range in Oaxaca, Mexico is no doubt the explanation. In any case, now a bit more is known, thanks to a recent paper by Gunther Köhler and colleagues in Breviora (freely available on the MCZ publications website).

The paper includes a detailed morphological description of the species, as well as notes on natural history and conservation status. Most interesting to me is the sexual dimorphism in dewlap size (males on top above, females below), which we have discussed in previous posts, and the aberrant patterning of one juvenile individual (right).

Here’s the abstract:

During three short visits to the coffee-growing region in the hills north of Pochutla (Oaxaca, Mexico), we observed Anolis macrinii in its natural habitat. The species appeared to be relatively abundant, and we collected 12 individuals, including several adult males. The holotype of this species was reported erroneously to be an adult male but actually is a female. The confusion might have arisen from the moderate-sized dewlap present in adult females. However, males have a very large dewlap and a pair of moderately to greatly enlarged postcloacal scales. We provide color descriptions in life for three individuals, color photographs in life, description and illustration of hemipenis morphology, and some natural history notes. Finally, we discuss the conservation status of this species.

SICB 2014: You Decide What To Read About

By Martha Muñoz

On December 5, 2013

In New Research

When AA contributors attend scientific conferences, we try our best to post about as many talks and posters as we can visit, but inevitably we simply can’t visit them all. I will be attending the annual meeting for the Society for Integrative and Comparative Biology this upcoming January. This will be the third consecutive year in which I blog about SICB and I want to try a different approach this time. Rather than choosing the talks and posters myself, I want to get your input on what types of research most interest you. If you like to read about new research presented at conferences, then please take the survey provided below. Choose up to three different subject matters and I’ll decide my schedule based on the results. You can access a list of anole-related presentations here. Most presentations can fit into more than one category, but I just want a general idea of what most interests the readers. Now go vote!

Explaining Changes To Species Names In Nicholson et al. 2012

By Rich Glor

On December 4, 2013

In Ask the Experts, New Research

I’m a little embarrassed to be writing this post, but I’m still unable to figure out some of the proposed changes to anole binomials in Nicholson et al.’s (2012) taxonomic revision of Anolis. I’m a real novice with implementation of “The Code” and the rules of the International Commission on Zoological Nomenclature, so I’m looking for a bit of help from AA readers who are more expert than I.

I understand that some of Nicholson et al.’s proposed changes to specific epithets are necessitated by the fact that their taxonomic revision would change the gender of generic epithets (e.g., Anolis chlorocyanus would be Deiroptyx chlorocyana due to the fact that Anolis is masculine and Deiroptyx is feminine). These types of changes are demanded by The Code’s article 31.2. However, I am struggling to understand Nicholson et al.’s proposed changes to twelve binomials that – to my novice eyes – do not appear to be due strictly to changes in the gender of generic epithets (see table below). Because the authors of this paper include leading authorities on taxonomy and nomenclature, I trust that these changes are not simply the result of typographical errors.

In most cases cited in my table, Nicholson et al. add or change vowels in the correct original spellings of species epithets, where the “correct original spelling” is defined under The Code as “the spelling used in the work in which the name was established.” Based on my amateur reading of The Code, changes to correct original spellings are not permitted unless it can be shown that the original spelling was inadvertently incorrect due to a printer’s error or related mistakes unrelated to the authors lack of familiarity with Latin (ICZN, Article 32). Can somebody enlighten me about which articles in the code govern the changes in the table below?

In this table, I provide the genus to which Nicholson et al. assign each species, the gender of this genus, the exact spelling for the specific epithet used in their manuscript, the spelling of the specific epithet from the Reptile Database, the spelling of the specific epithet from the original publication (NAs indicate that I have yet to check the original citation⁴), the type of change that Nicholson et al. have proposed, and the citation of the original description. Below the table, I provide some additional details about three specific cases. Thanks in advance for your help.

Genus	Gender	Nicholson et al.	Reptile Database	Original Spelling	Change	Description Citation
Anolis	Masculine	anfilioquioi	anfiloquioi	anfiloquioi	o to io	Garrido 1980
Anolis	Masculine	maclientus	macilentus	macilentus	e to ie	Garrido and Hedges 1992
Anolis	Masculine	pumilis	pumilus	pumilus⁴	u to i	Garrido 1988
Ctenonotus	Masculine	monoensis	monensis	monensis⁴	e to oe	Stejneger 1904
Ctenonotus	Masculine	nubilis	nubilus	nubilus⁴	u to i	Garman 1887
Dactyloa	Feminine	anatolorus	anatoloros	anatoloros	o to u	Ugueto et al. 2007
Dactyloa	Feminine	euskalerrari	euskalerriari	euskalerriari	ia to a	Barros et al. 1996
Deiroptyx	Feminine	domincanus [see comments for correction and clarification]	dominicanus	dominicanus	delete i	Rieppel 1980 [Note: the original version of this post incorrectly referenced de Quieroz et al. 1998]
Norops¹	Masculine	forbesi	forbesorum	forbesi	si to sorum	Smith & Van Gelder 1955
Norops	Masculine	schiedei [see comments]	schiedii	schiedii⁴	ei to ii	Wiegmann 1834
Norops²	Masculine	williamsi	williamsii	williamsii	ii to i	Bocourt 1870
Norpos³	?	parvicirculatus	parvicirculata	parvicirculata⁴	rops to rpos and a to us	Alvarex del Toro & Smith 1956

I have a bit more information about three cases in this table.

1. Anolis forbesi is the original spelling in Smith and Van Gelder (1955), but Michels and Bauer (2004) corrected this name to Anolis forbesorum due to the fact that this species is named after more than one person. Michels and Bauer (2004) suggest that this change is a “justified emendation” under Articles 31.1.2-3 and 33.2.2 of The Code. We know that at least one author of Nicholson et al. (2012) was aware of this report because Michels and Bauer thank Jay Savage for having provided thoughtful comments on their manuscript. I’m not sure why Nicholson et al. (2012) reject this proposed change by using forbesi.

2. Nicholson et al. (2012) delete the final ‘i’ from a species originally named Anolis williamsii, in spite of the fact that article 33.4 of the ICZN states that “[t]he use of the genitive ending -i in a subsequent spelling of a species-group name that is a genitive based upon a personal name in which the correct original spelling ends with -ii, or vice versa, is deemed to be an incorrect subsequent spelling, even if the change in spelling is deliberate.” Which part of this rule or related rules in The Code permits changes from ‘ii’ to ‘i’ under some conditions?

3. Nicholson et al. (2012) change both the generic and specific epithets of Anolis parvicirculata when they refer to this species throughout their manuscript as Norpos parvicirculatus (see pages 91 and 96). Although I have included this change in my table for completeness, it is the one change that I think we must attribute to a typo, even though the misspelling of Norops as Norpos appears at least twice. The change from parvicirculatus seems likely due to the fact that this species originally, and incorrectly, had a feminine rather than a masculine specific epithet.

4. This post was revised to include original spellings confirmed by Peter Uetz, thus no more NAs in the table. Thanks Peter!

Anoles Take Over SICB 2014

By Martha Muñoz

On November 23, 2013

In New Research

With all my preparations for Thanksgiving underway, I had almost forgotten that the highlight of the holiday season is upon us. I am referring, of course, to the annual meeting for the Society for Integrative and Comparative Biology (SICB). Unlike most scientific conferences, which tend to host their meetings during the summer, SICB bucks the trend and meets during the first week of January. To me what is most exciting about SICB is the diversity of work that is presented there. SICB draws biomechanists, ecologists, physiologists, and geneticists, among many others, under the same roof. Thus, for those of us who are interested in anoles, SICB is a one-stop shop for learning about what’s new and exciting in Anolis lizards. In recent years, anoles have had a very strong presence at SICB. At the 2012 meeting in Charleston, South Carolina, there were 26 anole-related talks and posters. Last year’s meeting in San Francisco saw a bit of a lull, as there were only 18 talks and posters focusing on anoles. The program for the 2014 meeting has just been released, and a few quick searches using the terms “Anolis” and “anole” turn up 22 talks and posters. I hope this means that the Anolis presence at SICB is back on the rise. I will be posting about as many talks and posters as I can visit, so stay tuned. The talks and posters are given in alphabetical order by author below.

Anolis talks and posters at SICB 2014.

Founder Effect Speciation Lives! New Experimental Results Revive Mayr’s Theory

By Jonathan Losos

On November 15, 2013

In New Research

Today’s post is only tangentially related to anoles, but it’s about a new paper that seems to have received relatively little attention, so I thought it worth writing about. The idea of founder effect speciation goes back to the writings of Ernst Mayr and historically has been very important in the development of ideas about how new species originate. However, in recent years FE speciation has fallen on hard times. Theorists have claimed it to be highly unlikely, lab experiments have failed to find much support for it. More than a few evolutionary biologists have declared the idea dead and buried.

As an aside, why talk about FE speciation in these pages? The answer is simple—at least a few anoles (e.g., the green anole, A. carolinensis, and the festive anole, A. sagrei) have routinely colonized islands in the Caribbean, and very likely many of these colonizations involve the arrival of a single, impregnated, female. If the FE speciation occurs, these Caribbean anoles might be a good place to look for it. Moreover, a recent experimental study on A. sagrei (of which I was an author) reported that founder effects could have persistent effects on morphology, at least over the several-year span of the study.

And that leads us to the study in question, by Daniel Matute of the University of Chicago (and soon to be faculty at the University of North Carolina). In a truly gargantuan experiment on laboratory fruitflies just published in the Journal of Evolutionary Biology, Matute showed that reproductive isolation can, in fact, evolve as a result of extreme and persistent founder effects. The extent of this study is truly mind-boggling. A founder effect was induced by taking a single male and female fruit fly and putting them in a vial. Then, from their eggs, a single male and female were randomly chosen to form the second generation. This was continued for 30 generations. Sounds like a lot of work, right? Well, catch this: Matute started this experiment with not a single vial containing two flies, but with 1000 vials in which he replicated the experiment–I’ve never heard of such a massive experiment (though some Drosophila-savvy friends say I need to read the literature more). Now, admittedly many of the populations went extinct very quickly because of the intense inbreeding—80% were gone by generation 5 and only 12% lasted the full 30 generations. But, still that’s a lot of Drosophila TLC.

Degree of reproductive isolation (as measured from mate choice trials). The red histogram is the distribution of reproductive isolation between founder effect populations and the parental population; blue is between individuals from parental populations. Approximately 100 out of 123 surviving founder effect populations had reproductive isolation values greater than zero.

Of the 123 surviving lines, 100 of the lines showed some degree or reproductive isolation (i.e., flies preferred to mate with members of their own population rather than with members of the parental population), and in 3 of the lines, in which 80% of the matings were with their own kind, this degree of evolution of reproductive isolation was found to be statistically significant. Note, too, that even though the degree of reproductive isolation (RI) was only statistically significant in those three lines, the mean degree of reproductive isolation of all FE lines from the parental (red line in figure to right) was greater than the degree of isolation in almost all parental x parental crosses. Or, looked at another way, a substantial number of FE lines evolved greater RI than seen in any of the parental crosses.

A number of perspectives can be taken on these findings. A conservative interpretation is that, at least very occasionally (0.3% out of 1000 initial founder events; 2.4% of 123 surviving populations), founder effects followed by very small population sizes for 30 generations can lead to the evolution of significant amounts of reproductive isolation. Given that the primary architects of FE speciation theory (Mayr, Templeton, others) have always said that FE speciation is a rare event, this result will be seen by many as supporting their position. Ardent proponents of founder effect speciation will go a step further and argue that the experiment provides at least suggestive evidence that founder effects can not infrequently lead to the evolution of enhanced reproductive isolation, given the relatively large number of populations with high degree of RI (see figure above). On the other hand, detractors will no doubt argue that the extremely stringent conditions imposed in the experiment, especially the maintenance of a population size of two for 30 generations, is both unrealistic of conditions likely to occur in nature and doesn’t closely model the theoretical ideas put forward by Mayr, Templeton, and others.

Although no doubt various camps will view these results in different ways, if nothing else, this is the first glimmer of support for FE speciation in a long time; it will be interesting to see whether the paper succeeds in putting founder effects back on the speciation playing field.