Category: New Research Page 13 of 66

Dewlap and genetic differences between co-occurring Anolis distichus and A. brevirostris

Dewlap and genetic differences between Anolis distichus and A. brevirostris at sites where they co-occur on Hispaniola.

Here at Anole Annals, we’re all familiar with the replicated evolution of different anole ecomorph types in the Greater Antilles. However, divergence into these different ecomorph classes is not enough to explain how the group became so speciose on these islands. Additional factors must therefore have promoted speciation throughout the history of the group.

One potential factor is the flashy anole dewlap. Dewlap diversification across anoles has led to the remarkable array of dewlap color, pattern and size we see today. If dewlap differences did indeed drive speciation in anoles, or are involved with the maintenance of species boundaries, we might expect that as differences in dewlap color and pattern increases between species, genetic differentiation will also increase through fewer hybridization events.

In our study that just came out in the Journal of Herpetology, Rich Glor, Anthony Geneva, Sabina Noll and I set out to test this using two widespread species from the Anolis distichus species complex, A. distichus and A. brevirostris. These two species co-occur in many locations on Hispaniola and, while they often differ in dewlap color where they do co-occur (yellow with an orange patch vs. all pale yellow), in other areas, they co-occur with similarly pale dewlaps. Using mitochondrial DNA, microsatellite and AFLP data, we investigated patterns of genetic differentiation at four sites: two where the species differ in dewlap color, one where the species share the same dewlap color, and another where pale dewlapped A. brevirostris co-occurs with two A. distichus subspecies (one with a similarly pale dewlap and the other with an orange dewlap).

In general, we found that A. distichus and A. brevirostris looked like “good species,” with strong genetic differentiation and little evidence of hybridization, even at a site where they share the same dewlap color. This suggests that dewlap color differences are not associated with genetic differentiation in a manner one might expect if dewlaps were involved in the speciation process or in maintaining species boundaries. However, at the site where A. brevirostris co-occurs with two A. distichus subspecies with both similar and dissimilar dewlap colors, we found some evidence of hybridization and the species were not as highly genetically differentiated. This discrepancy suggests that site-specific factors could be influencing the dewlap’s role in speciation or maintaining species boundaries. For example, as Leo Fleishman’s and Manuel Leal’s work has shown (e.g. 1, 2, 3), the dewlap’s effectiveness as a signal is dependent on the light environment. Further understanding about the environmental differences among our study sites, how species utilize the available light microhabitats within each site, and how the dewlap looks to anoles at each site could provide more insight into our findings.

On the other hand, perhaps we need to be looking beyond the dewlap and focusing instead on whole signaling displays. Anole behavioral displays can also be strikingly different among species (e.g. 1) and may instead be the key to understanding species diversification in Greater Antillean anoles.

Happening Now: The Latin American Congress of Herpetology

By Anthony J Geneva

On July 27, 2017

In New Research

The 11th Latin American Congress of Herpetology is underway right now at the Museo de Zoología QCAZ at Pontificia Universidad Católica del Ecuador. Although I could not attend, I have been following the meeting vicariously as attendees have been using the Twitter hashtag #latinherps to document the meeting. From those tweets alone, it appears the meeting has featured a series of fantastic talks, including many on anoles. If you are not a Twitter user you can still follow along by clicking more below to see all tweets from the Congress. Finally to Congress attendees, if any of you are interested, it would be great to have you contribute Anole Annals posts (or even comments below) on talks from the meeting.

JMIH 2017: Nobody Gets Tired of Looking for Anoles!

By mjohnson216

On July 20, 2017

In New Research

Amy Yackely Adams presents at JMIH 2017.

Amy Yackel Adams presents at JMIH 2017.

All anole field biologists have been there, right? It’s the middle of the night, and you’re walking around the forest searching for sleeping lizards in the trees. You’re probably wearing a headlamp, so the bugs are flying around your face, and your eyes start to strain as you get sleepy and you’re entering hour three or four of the search. This searcher fatigue could lead to the kinds of unintentional bias that can interfere with our research. But there’s good news when it comes to anoles, as Amy Yackel Adams, a statistician with the USGS in Fort Collins, Colorado, reported on the last day of JMIH.

Dr. Yackel Adams works with a Rapid Response Team whose goal is to prevent the spread of the worst invasive species. When a report came in of a sighting of a brown tree snake on the island of Saipan (in the Northern Mariana Islands, western Pacific Ocean), the team of experienced herpers deployed to Saipan and began intensive nightly surveys to assess the possibility of a brown tree snake population there. Luckily, they didn’t find any of these snakes in the surveys, but they did log 20,000+ sightings of other vertebrates! These included emerald tree skinks, several species of geckos, a variety of small mammals, and the green anole (Anolis carolinensis). Dr. Yackel Adams saw an opportunity to use this rich dataset to statistically test for two types of bias that could occur in such surveys – searcher fatigue (both across the 4-hour nightly searches, and across the up-to-31 day deployment), and searcher bias in taxon detection.

The team of 29 searchers covered a total of 387 km of transects during the 31 days, and found a total of 5,800 sleeping green anoles during this time. (Wow!!) In terms of short-term searcher fatigue, there was a slight decrease in tree skink and mammal sightings as the night progresses, and gecko sightings were generally stable over the night, but far MORE green anoles were sighted in the later hours of the night. And over the long term, skinks and anoles were MORE likely to be detected the more nights a searcher worked, and there was no evidence of long-term searcher fatigue. So, that’s why my take-home message was “nobody gets tired of looking for anoles!”

There was, however, significant taxonomic bias among the searchers – for example, the skink-to-anole sighting ratios ranged from 0.86 to 9.5. Dr. Yackel Adams concluded that this type of bias could be a real problem for certain kinds of studies, and we should be aware that differences among sightings by our survey team members could be potentially problematic in statistical analyses.

If West Indian Weevils Colonized the Mainland 19 Million Years Ago, Were Norops Anoles Along for the Ride?

By Christine Rose-Smyth

On July 19, 2017

In All Posts, New Research, Research Methods

Exophthalmus scalaris. Credit: symbiota4.acis.ufl.edu/scan

In their 2008 review “Are islands the end of the colonisation road?” Bellemain and Ricklefs (2008) concluded that oceanic islands could be important sources of colonisation of mainland continental areas and cited anoles of the Norops clade as a notable success. There are more than 5 times as many Norops clade species in Central and northern South America as in the West Indies; the 23 extant Caribbean species in the clade are distributed in Cuba and Jamaica with one species in Grand Cayman (Nicholson et al, 2005). Data in Nicholson et al (2005) gave support to the reverse colonisation hypothesis, but did not offer specific dating for the colonisation.

New analyses of 65 species in the Exophthalmus weevil genus complex (Zhang et al 2017) have turned up results that are of significance in understanding the biogeographic history of Caribbean anole dispersal and diversification. Like anoles of the Norops clade, the weevils show reverse colonization (island-to-continent), with diversification on the mainland and diversification within the islands. The data also give some support for overwater dispersal as the factor best explaining ancient between-island distribution.

Zhang et al’s best fit biogeographic model gives an estimate of 19Ma for a jump dispersal of Exophthalmus, most likely from Hispaniola, which went on to diversify into more than 40 species in Central America. So – did the anoles and the weevils make their journeys to the mainland around the same time and under similar conditions? Can this weevil study and the techniques it uses to arrive at its conclusions inform anole evolution and dispersal?

References

Bellemain, E and RE Ricklefs (2008) Are islands the end of the colonisation road? Trends Ecol Evol. 2008 Aug; 23(8):461-8. doi: 0.1016/j.tree.2008.05.001. Epub 2008 Jun 26. (Correction to citation numbering: Trends Ecol Evol. 2008 Oct; 23(10):536-7).

Nicholson, KE, RE Glor, JJ Kolbe, A Larson, S Blair Hedges, JB Losos (2005) Mainland colonization by island lizards. Journal of Biogeography 32 (6), 929-938.

Zhang, G, U Basharat, N Matzke, NM Franz (2017) Model selection in statistical historical biogeography of Neotropical insects—The Exophthalmus genus complex (Curculionidae: Entiminae). Molecular Phylogenetics and Evolution, 109, 226-239. DOI: 10.1016/j.ympev.2016.12.039.

JMIH 2017: Brown Anoles Thrive under Artificial Night Light

By mjohnson216

On July 17, 2017

In New Research

Chris Thawley presents at JMIH 2017.

For most of the history of life on earth, the only sources of light at night were the moon and stars. Yet with the invention and rapid spread of electric light, species around the world now face a novel evolutionary pressure: artificial light at night, or ALAN. Artificial light likely has an especially strong effect on animals in city habitats, such as the urban-adapted brown anole lizard, Anolis sagrei. Chris Thawley and Jason Kolbe at the University of Rhode Island set out to determine whether brown anoles were negatively impacted by ALAN.

In addition to their abundance in urban environments, brown anoles are a particularly good species for this study. Previous studies of brown anoles have shown that photoperiod influences the onset of reproduction at the beginning of the breeding season, and that several behavioral traits change under artificial light. In addition, work by Moore and Menaker has shown that pineal production of melatonin in this species is significantly altered by photoperiod. So, would ALAN influence brown anole growth and reproduction?

Chris and Jason collected lizards from south Florida and set up a lab experiment where some lizards experienced a normal photoperiod, and others were exposed to ALAN that mimicked landscape lighting. Their results were quite unexpected! ALAN actually increased female growth, resulted in eggs laid earlier in the season, and increased the reproductive output of small females – but did not affect the number or mass of eggs or hatchlings. And, ALAN females did not exhibit more stress (measured via circulating corticosterone) than control females.

So are brown anoles just superlizards? Do they have no trade-offs that result from ALAN? Chris suggested that it’s possible that such trade-offs may appear in studies over a longer time period, or in traits not measured here. Or, perhaps ad libitum food and the absence of predators in the lab remove the costs of ALAN. Or, maybe these really are indefatigable lizards!

JMIH 2017: Removal of Curly-tailed Lizards Increases Survival of Urban Brown Anoles

By Chris Thawley

On July 16, 2017

In New Research

Interspecific Interactions Between Two Species of Invasive Lizards in an Urban Environment; Camila Rodriguez-Barbosa and Steve Johnson

An extensive body of work has addressed the eco-evolutionary impacts of the Northern Curly-tailed Lizard (Leiocephalus carinatus) on Brown Anoles (Anolis sagrei) (much of it receiving coverage right here, here, and here on Anole Annals!). These species co-occur not only on many Caribbean islands where much of this research has taken place, but also within the urban matrix of southern Florida, where both species are introduced.

Camila Rodriguez-Barbosa and Steve Johnson investigated the impacts of curlies on brown anoles in shopping centers in southern Florida where both species were plentiful. Camila first collected baseline data on anole and curly populations at eight sites before embarking on a quest to eliminate curlies from four of her sites. Over the next four months, she removed over 300 (!) curlies from these sites, many of which had brown anole remains in their stomachs.

She found that this removal had serious consequences for brown anoles. Compared to anoles from shopping centers where curlies were unchanged, A. sagrei at removal sites experienced higher survival and consequently greater abundances. These anoles also shifted to lower perches once curlies were removed, mirroring results from previous work which show that the introduction of curlies leads to brown anoles occupying higher perches to escape this dangerous predator. Camila’s work suggests that brown anole/curly-tailed lizard interactions may be similar even in very different habitats and provides a fascinating look at lizard life (and death) in the urban sprawl of southern Florida.

JMIH 2017: Brown Anole Reproductive Output Varies Seasonally

By Chris Thawley

On July 16, 2017

In New Research

Tim Mitchell, Josh Hall, and Daniel Warner: Seasonal Shifts in Anolis sagrei Reproduction Invoke Challenges for Scientific Reproducibility

Sometimes a scientist just needs hundreds of hatchling anoles for an experiment. Tim Mitchell found himself in this position recently, and, like a good lizard ecologist, he started breeding colonies of anoles in the lab to produce eggs to incubate until hatching. As he created three different breeding colonies from brown anoles (Anolis sagrei) in central Florida, one each in February, June, and September, Tim found that he had also created an ideal situation in which to examine how the reproductive condition and output of brown anoles varies across the breeding season.

Tim, along with his coauthors Josh Hall and Dan Warner, found that females produced eggs with significantly greater mass later in the breeding season. These eggs took longer to produce than those earlier in the year (a greater interclutch interval), and the eggs resulted in hatchlings that had higher mass in relation to the weight of their eggs. These reproductive differences remained even after accounting for the fact that female anoles were also larger and heavier later in the year.

These findings suggest that female A. sagrei may shift their reproductive effort from producing a higher quantity of eggs (i.e., more, smaller eggs resulting in smaller hatchlings) in the beginning of the breeding season, to producing higher quality eggs (i.e., fewer, larger eggs resulting in larger offspring) later in the breeding season. Tim’s findings also stress the importance of investigating and accounting for seasonal differences when examining reproductive output in lizards.

JMIH 2017: Costa Rican Anole Ecology

By mjohnson216

On July 14, 2017

In New Research

Greetings from Austin, Texas, and the Joint Meeting of Ichthylogists and Herpetologists! Chris Thawley and I have appointed ourselves to be your AA reporting team from JMIH, and we’re aiming to post updates from each of the 8 anole talks and posters at this meeting.

Brian Folt

On the first day of the conference, there were two exciting talks on the ecology of Costa Rican anoles. The first was by Brian Folt, a graduate student in Craig Guyer’s lab at Auburn, who developed a model of predator-prey co-occurrence where one of the prey were anoles (Anolis (Norops) humilis) and the predators were…spiders?! Yes, wandering spiders, or ctenids, can prey upon the small anoles on the forest floor. (The other putative prey were poison dart frogs, who have a relatively similar life history to anoles.) Brian performed an extensive field study in 14 plots at La Selva Biological Station, conducting visual encounter surveys for anoles, frogs, and spiders, and recording arthropods in leaf litter samples. He used two-species occupancy models to determine how prey were affected by the presence of the predator and by resource abundance in the leaf litter. The result? Anole occupancy was lower where spiders were absent, and the detection probability of anoles was higher when spiders were present and detected. This suggests that anoles are responding behaviorally, such that they may increase their vigilance when predators are around.

Michelle Thompson

I then ran across the conference center to catch the next anole talk – a terrific presentation by Michelle Thompson, a graduate student in Maureen Donnelly’s lab at Florida International University. Michelle studied whether thermal quality differed across the stages of forest succession, and how that affected Anolis (Norops) humilis and A. (N.) limifrons distributions. She worked across transects of pasture, secondary forest, and old growth forest in both upland and riparian sites. Michelle measured the thermal quality of each habitat, the thermal preferences of the lizards, and the location and abundance of the lizards. She found that thermal quality was lowest in the pasture sites, as temperatures were frequently higher than the lizards prefer. Yet, in these pasture sites, riparian habitat with remnant trees provided a thermal refuge for the lizards. This kind of work can help us understand why and how species may respond differently to human-caused alterations in habitat structure and temperature in our changing world.

Stay tuned for updates from JMIH, and follow the #JMIH17 hashtag on twitter for more herp-related news!

Evolution 2017: Anoles and Ameivas Have Similar Gut Microbiomes

By Kristin Winchell

On July 5, 2017

In New Research

Late Breaking: one last Evolution 2017 post! Last weekend during the Evolution meeting, I had a chance to chat with Iris Holmes (Ph.D. student, University of Michigan) about the poster she presented. Initially not on our watch list because of the lack of “anole” in the description, my eye caught the dewlapping lizard perched at the top of her poster from across the room.

Iris presented her work on gut microbiomes of two groups of lizards: anoles and ameivas. She wanted to know if different taxa have different gut microbiomes and to what extent diet influences bacterial composition of gut microbiomes. Her collaborator (Ivan Monagan) collected scat samples from 22 Anolis dollfusianus and 9 Ameiva from an agricultural area in the Soconosco region of Chiapas, Mexico. Together, they then sequenced both the gut bacteria and the digesting prey with two 16S primers. Iris chose to target the prey as well because she wanted to know if they were eating different things and how different stages of digestion influence gut bacteria communities.

Iris found that there were no clear differences between the gut microbiomes of anoles and ameivas. Both species had gut microbiomes dominated by three main phyla: Proteobacteria, Firmicutes, and Bacteroidetes. Little is currently known about how these bacteria relate to digestion and health in reptiles, but Iris commented that we can make some guesses based on studies in other taxa. Proteobacteria are a disease indicator in mammals, but appear to be normal in reptiles and birds. Firmicutes and Bacteroidetes are both important for digestion of carbohydrates and fats (respectively) in mammals. Iris found that there was a loose correlation between the amount of prey consumed and the abundance of Bacteroidetes, suggesting these bacteria also play a role in digestion in lizards. She also found that there was an apparent tradeoff between the Proteobacteria and the two other groups – sequence abundance of proteobacteria was negatively correlated with abundance of Bacteroidetes and Firmicutes. Overall, this is an interesting first step in understanding the gut microbiomes of reptiles and how they differ (or don’t) between groups.

Metabolism Rate Data on Anoles?

By mjohnson216

On July 4, 2017

In New Research

I’m hoping that some of you out there have been collecting Basal Metabolic Rate or Resting Metabolic Rate data on Caribbean anoles!

I’m working with a group of scientists on a large-scale comparative database on circulating hormones in free-living vertebrates – we call our collaboration HormoneBase – and we’re hoping to look at relationships between hormone levels and metabolism. (We’ll be presenting some of this work at the Society of Integrative and Comparative Biology meeting in January 2018 – check out our symposium announcement here!) We have a good list of anole species in the database, thanks to the work of Jerry Husak and Matt Lovern (2014), but it seems that very little metabolism rate data are available for these species. Do you know of such data, or do you have them – published or unpublished? If so, please contact me (mjohnso9@trinity.edu)!

Reference:

Husak JF and MB Lovern. 2014. Variation in steroid hormone levels among Caribbean Anolis lizards: endocrine system convergence? Hormones and Behavior 65:408-415.