Author: James T. Stroud Page 3 of 6

I am most interested in understanding how different species of lizards live together. Specifically, I research the ecological mechanisms that facilitate coexistence and the subsequent evolutionary consequences. I am a post-doc in the Losos Lab at Washington University in St. Louis. Website: www.jamesTstroud.com

Jamaican giant anole (Anolis garmani) – one of the many non-native anoles you may see in Miami, FL.

In 2018 it will be nearly ten years since the last Anolis symposium was held at the Museum of Comparative Zoology at Harvard University. Given the rapid advances and exciting new discoveries in Anolis biology, it’s time to organize the 7th Anolis symposium! So, with this official announcement, please mark the weekend of March 17-18th 2018 in your calendars to come and visit the wonderfully tropical lizard-world of Miami, FL!

The aim of the symposium is to bring together Anolis biologists from diverse backgrounds to share their excitement and discoveries for these marvelous lizards. In this symposium, we hope to foster cross-disciplinary collaborations of people working with anoles and to broaden our general understanding of their biology and natural history. Miami was chosen not only for its spectacular anole diversity, but because of its ready access to anolologists living outside of mainland United States.

Miami, FL, is an ideal place in the USA to host this meeting! Over the past 100 years, eight species of Caribbean anoles have joined one native species in becoming established in south Florida. This meeting will be held on the weekend of March 17-18th 2018, which broadly overlaps with at least one weekend of the Spring Break holiday for most US schools, and does not conflict with other major meetings as far as we’re aware. We hope that this will facilitate good attendance! The symposium will be held at the Fairchild Tropical Botanic Gardens, which is home to a diverse community of exotic lizards, including six (!) species of anoles (read more about them here and on Anole Annals here!).

This post serves as a ‘save the date‘ – stay tuned the Symposium page for more information on conference registration, abstract submission for oral and poster presentations, and article submission for the Anolis Newsletter VII.

Puerto Rican crested anoles (A. cristatellus) in Fairchild Tropical Botanic Gardens

Evolution 2017: It Doesn’t Pay to Be Risky When Predators Are About

By James T. Stroud

On June 27, 2017

In New Research

Oriol Lapiedra opened up the penultimate day of Evolution by discussing his results of a recent field experiment in the Bahamas. In this project, Lapiedra and colleagues evaluated how inter-individual variation in behavior – specifically risk-taking – influenced survival. To do this, the research team took advantage of a well-understood model system in evolutionary ecology: brown anoles (Anolis sagrei) on islands with and without anole-predators (curly-tailed lizards; Leiocephalus carinatus) in the Bahamas. Male and female brown anoles were collected and subjected to a behavioural trial which measured the amount of time it took for a lizard to leave a refuge after being exposed to a predator. These observations were used to quantify each individual’s propensity to take risks. For example, those individuals that left their refuge shortly after seeing a predator were interpreted as being more ‘risky’ than more conservative individuals. Following these trials, each lizard was x-rayed to assess morphology and individually tagged, before being released onto one of 4 predator-free islands or 4 predator-present islands, all of which were currently void of anoles.

Lapiedra et al. started with a priori hypotheses that overall survival would be lower on those islands with predators, and those that did survive would be individuals considered less risky. After waiting 4 months, the research team returned to the Bahamas to collect all lizards from each island and see which individuals had survived. The authors report that, as expected, overall survival was lower on islands with predators, and that there was a significant relationship between behaviour and survival such that high risk-taking individuals had much lower survival when predators were present. This suggests that under those biotic conditions, natural selection operates against those riskier phenotypes. On closer inspection, this relationship was largely driven by a strong relationship in females, with no significant relationship existing between risk-taking behavior and survival of males.

Lapiedra et al. then contrasted these results by independently assessing how morphology was related to survival. The authors found that both risk-taking behavior and morphology influenced survival, however – and, important to this study – the relative effect of an individual’s risk-taking behaviour was much more influential on survival.

Lizards On The Loose: Middle School Students Help Track Invasive Anoles in Miami, FL

By James T. Stroud

On June 19, 2017

In All Posts

As you have heard before on Anole Annals, the Lizards On The Loose project involves middle school students conducting anole surveys in their back yards, school grounds, and local parks throughout South Florida. You can read more about the background and early results of this project in an earlier AA post which summarizes my talk at the Ecological Society of America’s (ESA) 2016 annual meeting.

Well, now we have updated results! Chris Thawley, a postdoc in Jason Kolbe’s lab and new member of the Lizards On The Loose team, has produced this video which explains what we have learned from the new data collected by students during their 2016-17 surveys. One species that we are particularly interested in is the Puerto Rican crested anole (Anolis cristatellus), whose distribution in Miami has been closely monitored since their introduction in the 1970s (see Kolbe et al. 2016 for a review of this species’ range dynamics in Miami). To our amazement, middle school students identified populations of crested anoles that were brand new to us! Watch below for more information:

Box Turtle Scavenges Green Anole!

By James T. Stroud

On May 26, 2017

In All Posts

My good friend Trace Hardin, a professional entomologist but also avid herper and snake breeder, just sent me these photos below. Here’s what he had to say about the encounter on Instagram:

hardinherpetologica: Interesting observation while walking through the woods. Found this #BoxTurtle eating a dead #GreenAnole. I’m assuming it was a scavenged find but the entire body was gone by the time I came upon the scene. #Neature

Has anyone else observed box turtles (or any other chelonian [I guess now testudine?]) interacting with anoles?

Predation of a Gecko by Anolis pulchellus in the British Virgin Islands

By James T. Stroud

On March 28, 2017

In Natural History Observations, Notes from the Field

In the most recent issue of Herp Review, Anole Annals stalwarts Kevin de Queiroz and Jonathan Losos documented their account of observing an adult female grass-bush anole (Anolis pulchellus) consume a dwarf gecko (Sphaerodactylus macrolepis) on Guana Island, British Virgin Islands. The authors share their detailed report below:

Many primarily insectivorous lizards will eat other vertebrates on occasion, a behavior that has been reported in many species of Anolis. One unifying generality is that such carnivory is size structured, with the predator usually being substantially larger than the prey (Gerber 1999. In Losos and Leal [eds.], Anolis Newsletter V, pp. 28–39. Washington University, Saint Louis, Missouri). Not surprisingly, reports of anole carnivory pertain primarily to middle-sized and larger anoles. Here we report carnivory by a small anole of the species A. pulchellus. To our knowledge, this is the first instance of carnivory reported for this species and one of few for any similar-sized anole (the record noted by Henderson and Powell 2009. Natural History of West Indian Reptiles and Amphibians. University Press of Florida, Gainesville, Florida. 495 pp. is based on the observations reported here).

Fig. 1. Female Anolis pulchellus in the process of ingesting a
Sphaerodactylus macrolepis.

We observed a female A. pulchellus (SVL ca. 38 mm) capture and consume a Sphaerodactylus macrolepis (SVL ca.18 mm) in the leaf litter at approximately 1430 h on 25 September 2006, on Guana Island, British Virgin Islands, near the head of the Liao Wei Ping Trail at roughly 18.47916°N, 64.57444°W (WGS 84). The anole jumped from a low perch (ca. 20 cm above the ground) to the ground and bit the gecko, which escaped and fled 15–20 cm to the opening of an ant nest. The anole attacked the gecko again, seized it in its mouth and carried it approximately 10 cm up a vine, a distance of 15–20 cm from the site of attack. Initially, the anole held the gecko upside down (i.e., dorsal surface facing down), biting it between the fore and hind limbs on the left side. Eventually the anole worked its grasp posterior to the base of the tail, still on the left side. At this point, parts of both the base of the tail and the left hind limb were in the anole’s mouth (Fig. 1). The anole then manipulated the gecko so that it was no longer upside down, but rotated about its long axis by roughly 90 degrees (the ventral surface of the gecko was then oriented forward relative to the anole) at which point it was biting the gecko at the base of the tail and possibly by the left hind limb; the anole eventually manipulated the gecko so that it held it tail-first in its mouth, dorsal side up, at which point the anole proceeded to ingest the gecko tail first (during this time, the tail itself broke off and was carried away by ants, which had been biting the gecko in several places since shortly after it was
captured by the anole). Total time from capture to complete ingestion was approximately five minutes.

Predation on Sphaerodactylus geckos has been reported in anoles of only a few species, none of which are as small as Anolis pulchellus (Henderson and Powell 2009. Natural History of West Indian Reptiles and Amphibians. University Press of Florida, Gainesville, Florida. 495 pp.). However, given the size discrepancy between the lizards in these two clades and their extensive coexistence across the Caribbean, we suspect that such interactions may occur with some frequency. Moreover, the high population densities of some Sphaerodactylus geckos (e.g., Rodda et al. 2001. J. Trop. Ecol. 17:331–338) and the diurnal activity of several species (Allen and Powell 2014. Herpetol. Conserv. Biol. 9:590–600) suggest that they may be important prey items for anoles.

References
– Allen, K.E. and Powell, R., 2014. Thermal biology and microhabitat use in Puerto Rican eyespot geckos (Sphaerodactylus macrolepis macrolepis). Herpetological Conservation and Biology, 9(3), pp.590-600.
– Gerber 1999. In Losos and Leal [eds.], Anolis Newsletter V, pp. 28–39. Washington University, Saint Louis, Missouri
– Henderson and Powell 2009. Natural History of West Indian Reptiles and Amphibians. University Press of Florida, Gainesville, Florida. 495 pp.
– Rodda, G.H., Perry, G.A.D., Rondeau, R.J. and Lazell, J., 2001. The densest terrestrial vertebrate. Journal of Tropical Ecology, 17(02), pp.331-338.

Early Breeding Season Injuries through Aggressive Interactions in Miami, FL

By James T. Stroud

On March 12, 2017

In All Posts

It’s currently dewlapping mayhem down here at the moment, with all species except the late-rising Cuban knight anoles (A. equestris) out and showing off!

An adult male Puerto Rican crested anole (A. cristatellus) performing dewlap extension displays in Miami FL

Visual displays such as dewlap extensions are often used to mediate physical interactions by acting as an indication of the relative size, strength, and fitness of each individual. This is beneficial for both parties; dominant individuals do not have to waste energy that a physical interaction would require, and weaker individuals avert the risk of physical injury (of course, both reasons are reciprocal to both individuals also).

However, when two individuals cannot determine dominance through visual communication, for example if two individuals are equally matched in size, then an aggressive and physical confrontation may occur (read a previous account of one such interaction between two equally-sized males here). The results of these interactions are apparent in many injurious forms, for example through extensive bite marks to the body (as previously discussed here and here), or perhaps even to the extent of tail loss (as discussed here).

Yesterday (9 March 2017) I observed this male Puerto Rican crested anole (A. cristatellus) below that looks like another male had taken a good bite at him!

Of course, there are many avenues through which such an injury may appear. However, the presence of a still-erect nuchal crest paired with how fresh the wound looks (and the time of year!) gives me the impression that this was probably the result of an intraspecific male-male interaction.

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

By James T. Stroud

On September 1, 2016

In Natural History Observations, New Research, Notes from the Field

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.

ESA 2016: Top-Down Effects of Brown Anoles on Islands Following Hurricanes

By James T. Stroud

On August 28, 2016

In All Posts

Following up with summaries of anole talks at ESA 2016, Dave Spiller presented a broad summary of his and his colleague’s (Tom Schoener and Jonah Piovia-Scott) research investigating the effects of hurricanes on long term food web dynamics of small Bahamian islands, which has just recently been published in Ecology (see Spiller et al. 2016).

Spiller opened by explaining some of the patterns of food web dynamics that have been learned from this research. Most notably, that the elimination of brown anoles – which act as top predators in these simple ecosystems – leads to increased levels of herbivory as arthropods experience a relaxation of predation pressure (Spiller and Schoener 1990).Specifically, the presence of a common moth (Achyra rantalis) on islands without brown anoles can lead to extreme levels of herbivory upon a common island plant, Sesuvium portulacastrum (below).

Spiller and his colleagues began to notice that following hurricanes, one of the most extreme natural disturbance events in this region, islands with lizards experienced a much more rapid recovery of Sesuvium .

In an attempt to understand how ecosystems may be stable despite experiencing extreme disturbance regimes, Spiller and colleagues measured the percent ground cover of Sesuvium and abundance of Achyra moths on 11 islands with lizards present and 21 islands without lizards annually for 10 years.

Overall abundance of Achyra was 4.6 times higher on no-lizard islands than on lizard islands. The percent cover of Sesuvium exhibited lower temporal variability on lizard islands when the study site was undisturbed by hurricanes, and higher recovery rate on lizard islands following hurricanes.

Spiller concluded by suggesting that these stabilizing phenomena are linked to a trophic cascade in which predators (brown anoles) control herbivores (Achyra moths), and therefore enhance plant recovery following hurricanes.

ESA 2016: Niche Partitioning and Rapid Adaptation of Urban Anoles

By James T. Stroud

On August 17, 2016

In New Research

Maintaining an already-impressive 2016 conference tour de force which included presentations at both JMIH and Evolution, Kristin Winchell presented a broad summary of her urban anole research in an invite-only Urban Ecology session at ESA 2016.

This presentation provided a synthesis of two large research projects both independently reviewed on Anole Annals (1,2), and so I will provide only a brief summary here. Kristin began by presenting an over-arching question in modern ecology: how is urbanisation going to affect biodiversity? While many may intuitively think of the process negatively, there is a large (and growing) body of research suggesting that many species are able to behaviourally respond to these novel environments and persist. So what about anoles? Kristin focuses her research on two Puerto Rican species: the crested anole (Anolis cristatellus) and the barred anole (A. stratulus).

To do this, Kristin and her team employed multiple methods to explore if a) these two species have differences in their ecology in urban vs. natural areas, b) if differences in ecology are observed, does this lead to differences in morphology, and c) if differences in morphology are observed, is this related to performance? Firstly, niche partitioning between these two species in natural vs. urban areas was investigated (more details here).

This niche partitioning research is new and will be the main body of a manuscript currently in prep so I will keep discussions brief. One species, A. cristatellus, was observed to significantly shift its microhabitat use, which resulted in adaptive shifts in morphology. This research was documented in Winchell et al.’s recent Evolution paper and reviewed previously on AA (1,2,3). Specifically, urban lizards have longer limbs and stickier toepads (higher number of subdigital lamellae) in response to perching on broader, slippier substrates.

This research has now developed on to the next stage of performance-related investigations. Kristin is asking the question of whether these observed morphological shifts lead to better performance (and therefore, presumably, higher fitness). Kristin presented some preliminary results, but keep your eye out for more developments!

JMIH 2016: Variation and Distribution of Anolis roosevelti

By James T. Stroud

On July 11, 2016

In All Posts

One of the few known Anolis roosevelti specimens.

Anole stalwart Greg Mayer gave a wonderful talk discussing the distribution and morphology of the large and maybe-extinct Anolis roosevelti. A. roosevelti, commonly known as the Culebra Island giant anole, was first described in 1931 by Chapman Grant, a US Army Major and practising herpetologist, from a single adult male specimen collected on Culebra. Although Reinhardt and Lutken, in 1863, had already provided an accurate description of A. roosevelti, but under an alternative name of A. velifer.

Reinhardt and Lutken’s specimens were collected from Vieques, Tortola, and St. John, although Greg having the opportunity to study them meant tracking them down to natural history collections in both Copenhagen and Stockholm. In total, this entire species is known from eight specimens, only six of which are still in existence (Greg had the opportunity to study all six, meaning he’s now seen more roosevelti than any other anolologist?). Greg explains that roosevelti based on the limited information provided by Dimas Villanueva, who collected the holotype, and his own investigations, roosevelti can be classified as a “crown-giant” ecomorph. This means that the eastern islands of the Puerto Rico bank had a series of four ecomorphs, with roosevelti being what Ernest Williams termed a climatic vicariant of cuvieri, occuring in (and presumably being adapted to) the more xerophytic forests of the eastern bank islands.

The known distribution of Anolis roosevelti.

Greg went on to describe the morphological features which distinguish A. roosevelti from a A. cuivieri, an ecologically and morphologically similar species from neighbouring Puerto Rico. Roosevelti is a larger, brownish gray rather than green as is seen in cuvieri (although check out these gray cuvieri preveiously mentioned on AA). Roosevelti generally has larger head scales, and a more elongate and deeply grooved head – these differences are confirmed in the ANCOVA analyses below.

So, what chances are there of seeing roosevelti in the wild? Low, probably. No specimens have been collected since 1932, and several researchers, including Greg, have recently scoured both Vieques, St. John and Tortola but with no success. By far the most extensive searches have been conducted by Ava Gaa, who exhaustively searched Culebra (totalling 1500 hours of looking!) as well as short visits to Vieques and St. John all with no success. Tantalising reports of potential candidates turned out to be juvenile green iguanas. Greg concludes by recommending that the long-protected and relatively poorly explored eastern half of Vieques may hold the secret to if any populations remain.