Tag Archives: anolis distichus

Signals and Speciation: Do Dewlap Color Differences Predict Genetic Differences?

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, 23), 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.

Ecology of the San Salvador Bark Anole (Anolis distichus ocior)

 An adult male San Salvador Bark Anole (Anolis distichus ocior) displaying. Photograph by Guillermo G. Zuniga.

An adult male San Salvador Bark Anole (Anolis distichus ocior) displaying.
Photograph by Guillermo G. Zuniga.

Dayton Antley and colleagues from Avila University, the home of AA stalwart Bob Powell, recently published a detailed study of the ecology of the San Salvador bark anole (Anolis distichus ocior) in IRCF Reptiles & Amphibians (an open-access herpetological journal, with this article available here). Anolis d. ocior is one of 17 recognized subspecies of the diverse distichus group, and is found on only San Salvador and Rum Cay (Henderson and Powell 2009).

Antley et al. assessed microhabitat use, activity patterns, and approach distances of A. d. ocior in an approximately 0.3ha study area on the grounds of the Gerace Research Centre, dominated by Tropical Almonds (Terminalia catappa), Papaya (Carica papaya), and Ficus trees.

A Google Map view of the Gerace Research Centre. The study site (24°07'05.2"N 74°27'50.9"W) is outlined in white.

A Google Map view of the Gerace Research Centre. The study site
(24°07’05.2″N 74°27’50.9″W) is outlined in white.

In assessing patterns of microhabitat use throughout the day, Antley et al. conducted surveys every two hours for two days from 0700h (about 40 min after sunrise) to 1900h (about 40 min before sunset). Size class, perch height and diameter, body orientation relative to the ground, and thermal microsite (sun/shade/mixed) were recorded for every observed lizard. In the following two days, approach distances were assessed. This was achieved by a surveyor, wearing neutrally-coloured clothing, approaching an undisturbed anole at a steady pace and recording the distance at which the lizard reacted. Over two additional days, 10-minute focal animal observations were conducted of individual adult lizards (including both males and females) at a distance of 5m. The number of movements (changes in location or orientation), head turns, and head bobs were recorded for all lizards, with dewlap displays and pushups being additional recorded for males.

Lizards were active throughout the day, with activity peaking in the early morning and before midday. This was compared to ambient air temperatures recorded 1m from the ground in a shaded and sheltered location. This result surprised the authors, as a second activity peak in late afternoon/early evening was expected, as has observed in other similar studies of bark anoles (e.g. Hillbrand et al. 2011).

Mean number of lizards active (bars) and mean ambient temperatures (dots) per time period. Temperature data were collected on two consecutive days.

Mean number of lizards active (bars) and mean ambient temperatures
(dots) per time period. Temperature data were collected on
two consecutive days.

Adult males experienced highest levels of arboreality during the middle of the day, while subadult males and adult females (grouped together as they can be hard to distinguish from distance) were highly variable (see figure below). Most lizards of all classes were found in the shade, which the authors attributed as evidence for thermal conformity, and facing downward towards the ground, a common trait in many anoles that is most commonly perceived to increase an individual’s ability to monitor potential predators, competitors, or mates. 43% of lizards, however, were observed facing upwards. The author’s note that this behavior is often interpreted as an individual prepared for escape; however as all lizards were observed from distance and undisturbed, they (admirably) explain that this result is difficult to interpret.

A: Mean perch heights (cm) of adult males (L) and subadult males and females (S); B: mean perch heights of adult males at different times of day; C: mean perch heights of subadult males and females at different times of day.

A: Mean perch heights (cm) of adult males (L) and subadult males and females (S); B: mean perch heights of adult males at different times of day;
C: mean perch heights of subadult males and females at different times of day.

Adult male lizards were bolder than smaller subadult males and females, and retreated at a much closer distance when approached by a surveyor (0.99m +/- 0.07m vs. 1.54m +/- 0.18m). Focal observations revealed no significant differences between adult males vs. subadult males/females in shared behaviors, although there was a high variation in the amount of displaying behavior between adult males. The average time spent conducting dewlap displays was 3%, although one male was recorded investing 47% of his time in a combination of dewlap extensions and pushup displays.

Using all survey data combined, Antley et al. estimate that A. d. ocior in this study plot had a population density of 593 individuals/ha, with lizards observed on all but four of the smallest trees surveyed. Antley et al. note that their density estimate is extremely conservative, and much lower than previously published estimates (e.g. 1.070-5,460 individuals/ha, Schoener and Schoener 1978). The authors suggest that the small size of the study plot may have contributed to the relatively low density.

In all, this is a charming (although admittedly short) study of the natural history of the San Salvador bark anole (A. d. ocior) – a great example of an undergraduate research project that follows through to publication!

References
– Antley, D.L. et al. 2016. Microhabitat, Activity, and Approach Distances of the San Salvador Bark Anole (Anolis distichus ocior). IRCF Reptiles & Amphibians 23(2): 75-81
– Henderson, R.W. and R. Powell. 2009. Natural History of West Indian Reptiles and Amphibians. University of Florida Press, Gainesville, Florida.
– Hillbrand, P.A., A.T. Sloan, and W.K. Hayes. 2011. The terrestrial reptiles of San Salvador Island, Bahamas. Reptiles & Amphibians 18: 154–166.
– Schoener, T.W. and A. Schoener. 1978. Estimating and interpreting body-size growth in some Anolis lizards. Copeia 1978: 390–405.

Bark Anole Battle Scars in Miami, FL

As it starts to heat up here in Miami, anole interactions are at the highest while males try to stake their claim for the most attractive territories in town. Earlier during an afternoon stroll around South Miami I came across this bark anole (Anolis distichus) that looks like it’s had a pretty rough time recently!

IMG_2873

I assume this injury to his nape is probably from another lizard, likely another male A. distichus, incurred during a territorial dispute, and not a predation attempt. Either way, it looks like it didn’t dent his confidence too much!

IMG_2878

Fill In The Blank: Obscure Anole Life History Traits

In collaboration with the Conservation Biology course taught by Dr. Karen Beard here at Utah State University, where I am a Ph.D. student, I have been involved in gathering life history data on ~400 species of reptiles that have been introduced outside of their native ranges for an analysis of how life history traits (e.g., diet, fecundity, longevity) interact with other factors to influence the likelihood of successful establishment. Appendix A of Fred Kraus’ 2009 book Alien Reptiles and Amphibians is the source of the species list we are using, and included in this analysis are 26 species of Anolis. This is where you come in.

First, we coded all anoles as (i) sexually-dichromatic, (ii) diurnal, (iii) non-venomous, (iv) oviparous, (v) omnivores that lack (vi) temperature-dependent sex determination and (vii) parthenogenesis. Is anyone aware of any exceptions to these seven generalizations?

Second, we searched for data on clutch size, clutch frequency, incubation time, and longevity. The Anole Classics section of this site and the Biodiversity Heritage Library were particularly useful. After conducting what I feel to be a pretty thorough literature scavenger hunt, I am forced to conclude that some of these data simply do not exist at the species level for all of the species we’re interested in, or are not explicitly stated in a way that is obvious to a non-anole-expert. Of course, there is a lot of literature, including many books that I don’t have access to, and there are also lots of credible observations that don’t get published. I’m hoping that some of the readership here can help fill in at least some of the blanks in the table below. As one member of the team, I did not collect all of the data that are filled in myself, nor have I personally vetted every value, so if you spot an error please do point it out.

Two important points:

  1. Many environmental factors obviously influence the life history parameters of our beloved and wonderfully plastic reptiles, so we appreciate that many of these values would be better represented by ranges and are dependent on latitude, altitude, climate, and many other factors. Where a range is published, we are using its median value.
  2. I should also emphasize that, because of the large size of this study and the diversity of taxa included (ranging in size from giants like Burmese Pythons, Nile Crocodiles, and Aldabra Tortoises to, well, anoles and blindsnakes), it is more important for the data to reflect the relative values of these life history parameters across all anoles (and all reptiles) than it is to specifically and precisely represent all known variation within a given species of anole.

Without further ado (for your enjoyment, and because I know from my own blog that nobody reads posts lacking pictures, I’ve embedded an image of each species):

Species Median clutch size Median clutches per year Incubation time (days) Maximum longevity (months)
A aeneus
A. aeneus
2
A baleatus
A. baleatus
A bimaculatus
A.bimaculatus            
2 43 84
A carolinensis
A. carolinensis
1.15 6  41.5 65
A chlorocyanus
A.chlorocyanus
1 18
A conspersus
A. conspersus
1
A cristatellus
A. cristatellus
2.5 18 83
A cybotes
A. cybotes
1 18 45
A distichus
A. distichus
1 16 45.5
A equestris
A. equestris
1 1 48 149
A extremus
A. extremus
A ferreus
A. ferreus
1 18
A garmani
A. garmani
1.5 18 67
A grahami
A. grahami
1
A leachii
A. leachii
A lineatus
A. lineatus
A lucius
A. lucius
1 3.5 60
A marmoratus
A. marmoratus
2  50
A maynardi
A. maynardi
A porcatus
A. porcatus
1 18 63.5
A pulchellus
A. pulchellus
1
A richardii
A. richardii
1
A sagrei
A. sagrei
2 20  32 22
A stratulus
A. stratulus
A trinitatis
A. trinitatis
2  50
A wattsi
A. wattsi
1

Thanks in advance. I think this is a great blog and I hope to post something more interesting on here soon.

Dewlap Color, Gene Flow, Habitat Specialization, and Speciation: A Tale of Two Contact Zones

Dewlap variation in Anolis distichus in Hispaniola. The photos at the bottom show the change in dewlap color along the two transects in the recent study by Ng and Glor.

Despite all of the research on anole evolution conducted in the last 40 years, one important question still eludes us: how does speciation in anoles occur? This, of course, is of fundamental importance, because the great species richness of these lizards implies that speciation has run rampant in this group. So, we’d like to know why.

We don’t know much about speciation in anoles, but we do know a little. First, it is thought that the dewlap plays an important role. Sympatric anole species almost never have identical dewlaps, and experimental and observational evidence suggests that anoles use their dewlaps for species-recognition. Hence, understanding anole speciation may, to a significant extent, reduce to understanding the factors that cause populations to evolve differences in their dewlaps.

A different perspective on anole speciation relates to the classic question of whether allopatry is necessary or whether, as suggested by many recent studies, natural selection driving differentiation—whether in allopatry or not—is a more important stimulus to genetic differentiation. Recent work in the Lesser Antilles by Thorpe and colleagues has argued that environmental differences are the primary drivers of genetic differentiation within anoles, a result also suggested by Leal and Fleishman’s studies on A. cristatellus in Puerto Rico.

In this light, perhaps the most enigmatic anole is Anolis distichus of Hispaniola. Continue reading Dewlap Color, Gene Flow, Habitat Specialization, and Speciation: A Tale of Two Contact Zones

Stills from Anole Fight Along the Rio Bani!

These stills are of an anole fight we saw yesterday along the Rio Bani. This fight happened on a rock between two male Anolis distichus ravitergum. On the left, the two males are facing off. In the middle, one male is charging and biting the other. On the right, the two are tumbling down the boulder. Shea Lambert recorded the video and plans to post a version with slow-motion and music sometime soon; it should be epic.

Anole Research Cleans Up on Awards at JMIH

A figure illustrating dewlap color variation in the distichus species group from Anthony Geneva's award winning poster.

Two posters on anole evolution presented at JMIH last weekend were honored with SSAR poster awards.  Anthony Geneva, a PhD student at the University of Rochester took home the prize in the Evolution, Genetics, & Systematics category for his poster on “A Multi-locus Molecular Phylogeny of Distichoid Anoles.”  Mingna Zhuang, an undergraduate researcher at UC Berkeley, won in the Ecology, Natural History, Distribution, & Behavior category for her poster on “Comparative Gliding Performance of Anolis carolinensis and Anolis sagrei.”  Although not on anoles, it also bears noting that Daniel Scantlebury’s study of adaptive radiation in Sphaerodactylus – which has been inspired partly by work on Anolis – won the SSAR’s Henri Seibert Award for best student talk on Evolution/Systematics.  Congrats to Anthony, Mingna, and Dan!

Anoles of the Florida Keys

Not an anole, but plays one on TV. Photo from Dust Tracks on the Web (http://dusttracks.com/)

Janson Jones is at it again. Having just driven about as cross-continent as you can get, from Alaska to the Florida Keys, he is now waxing eloquent on the lizards of that delightful island string. Today’s post is about introduced green iguanas, which apparently are everywhere and spreading, but yesterday he posted twice, on brown anoles (A. sagrei) and bark anoles (A. distichus) , with some keen observations on interactions between the two. Most notably, he’s noticed on multiple occasions that the larger browns chase off the the daintier barks.

postscript: Just as I hit the “post” button, Jones put up another of his own, with further observations on bark anoles and outlining what would make an excellent Ph.D. dissertation project. Plus, this intriguing observation:

“…the iPad of anoles in the Florida Keys. They’re right on the edge, living in the third space, transitory ground between the browns on the ground and the greens in the trees. They’re not iPhones, but they’re not desktops either. Right in the middle — and perhaps drawing business from both sides?”

Bark anole, A. distichus, from Dust Tracks on the Web

Great Tales of Florida Anoles

From Dust Tracks on the Web

In a recent post, AA mentioned Janson Jones’ (Dust Tracks on the Web) report on catching a magnificent knight anole. Turns out that Jones is not only a kindred spirit, but a keen observer and an excellent photographer. Over the course of the last few days, he has posted a series of stories of observations of Florida anoles that are worth checking out.

Just a few comments. In “Clash of the Anole Titans” (photo above), he tells of a territorial battle between two male green anoles. Ultimately, the fight concludes when one male loses his grip and falls to the ground. Those who study the functional capabilities of anoles are always surprised at the great sticking ability of the anole toepad, much greater than is needed to support the lizard’s body weight (anoles can hang from a single toe!). Perhaps this ability has evolved, not for every day living, but for exceptional circumstances, such as prolonged, hand-to-hand combat or hanging on to a mini-van. Continue reading Great Tales of Florida Anoles