Hope you all are doing great. I just finished my finals and two applications to PhD programs (so far) so fingers crossed for me???
I wanna talk about another (mostly) brown-coloured anole today since I feel like there’s not enough appreciation for them.
Anolis distichus, the Bark Anole, is a trunk anole with about 16 subspecies, that ranges in colour from brown to grey to green. Their dewlaps also vary in colour and pattern with their population. Males and females look the same, but in this species only males have a dewlap.
Found in Haiti, Dominican Republic, central Bahamas and, of course, Florida, these anoles can be found in range of habitats. Bark anoles are kind of on the small side at about 127mm in length.
My favourite thing about the Bark Anole is the patterning that gives it its name. The striping mimics the roughness and shapes found in tree bark, making it kind of invisible sometimes. Quite an example of perfect camouflage.
There’s been a lot of research on the anole, particularly looking into its subspecies and if any of them are their own species. Currently, this doesn’t seem to be the case quite yet.
Maybe. There’s a lot of conversation about just how muchvariation there is or isn’t with this species.
Daisy Horr, an undergraduate researcher at Trinity University, discusses how bark anole behavior varies across several different social contexts.
Animals often use diverse behavioral repertoires to adjust to new, unexpected, or changing conditions very quickly. While it may seem like individuals could always use the best behavior for any given situation, we know that instead behaviors are often related within an individual. In other words, an individual’s behaviors are not always independent and may represent an underlying “behavioral syndrome” or correlated set of behavioral responses to related environmental conditions. These behavioral syndromes are also sometimes called “personalities” (though application of this word to animals can be a bit controversial!). So, for instance, an individual that has a “bold” behavioral syndrome might take little time to explore a new habitat or consume a novel food item more quickly, but also be more likely to stay active in the presence of a predator rather than hiding (the safer option!).
While anoles have been the focus of much behavioral research, we still lack an understanding of the diverse behavioral phenotypes, including behavioral syndromes, which are displayed by a variety of anole species. The bark anole, Anolis distichus, is native to Hispaniola but also found in southern Florida where it has been introduced. While small, bark anoles can be quite feisty, and are known for their dramatic display behavior in the presence of male and female conspecifics.
Male bark anoles demonstrate pushup displays prior to engaging in combat.
Taking advantage of the bark anole’s willingness to put on a show, Daisy Horr, an undergraduate student and McNair Scholar in Michele Johnson’s lab at Trinity University, led a group of fellow researchers in assessing whether these anoles show behavioral syndromes. To do this, Daisy and her collaborators measured the degree to which male bark anole behaviors were repeatable across three different contexts: trials with another male present, trials with a female present, and solo trials in which no other anoles were present. They measured variables quantifying movement as well as display behaviors such as pushups and dewlap extensions during these trials. The team also wanted to see whether the measured behavioral traits were linked to morphological and physiological variables.
Daisy and colleagues found no support for the idea that behavior was linked to morphology, including size of the body, head, and dewlap, and mass of the whole body, the liver, and fat pads (structures holding fat as energy reserves), or the hematocrit of the lizards, a metric quantifying how many red cells are present in the blood. Bark anoles did show some level of behavioral consistency, however. Movement behaviors were quite repeatable even between trials with and without conspecifics. Display behaviors, however, including pushups and displays, were repeatable within, but not across contexts. This work suggests that bark anoles have consistent behavioral syndromes in some contexts. Looking forward, research into behavioral syndromes in anoles could offer insights into how behavior may vary with habitat use, ability to invade novel environments, or selection on behavior itself!
The Bark Anole (Anolis distichusignigularis) from the Río Recodo. Photo from Richard Glor’s Flickr.
The Bark Anole (Anolis distichus) is a highly polymorphic lizard widely distributed in Hispaniola. Anolis distichus is divided into 16 subspecies with dewlap colors ranging from deep wine red to pale yellow (Glor and Laport 2012). In the early days scientists, such as Albert Schwartz, argued that A. distichus is divisible into multiple subspecies according to an analysis of variation in body color and dewlap pigmentation. But, are they really subspecies?
During the 2018 Joint Meeting of Ichthyologists and Herpetologists (JMIH),Richard Glor shared his lab’s advances on the curious case of Bark Anoles. Anolis distichus populations have ecological, phenotypic and genetic differences. Previous studies show a correlation between dewlap phenotype and environmental variation; in drier habitats, lizards have smaller, brighter, yellow dewlaps, while those in wetter habitats have larger, less bright, orange dewlaps (Ng et al. 2012).
Previously, the Glor Lab found strong support for the hypothesis that A. distichus is comprised of numerous genomically distinct populations (MacGuigan et al. 2016). Genetic divergence was associated with a biogeographic barrier, but not with dewlap color. Also, they found evidence for hybridization in contact zones with limited gene flow and intrinsic reproductive isolation between subspecies (MacGuigan et al. 2016; Ng et al. 2016). Overall, these studies suggest that geographic isolation, as well as ecological specialization, contribute to speciation.
The Glor Lab continues putting together the pieces of the puzzle. Most recently, they sequenced and assembled whole genome sequence data for A. distichus to identify the genomic basis for species differences and speciation.
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.
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.
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.
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.
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!
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!
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
