Category: All Posts Page 76 of 148

Reptiles are often thought of as solitary and not social animals. However, all of us who study anoles know that Anolis are anything but solitary animals. Spend a few minutes observing an anole and you might see it dewlapping, doing push-ups, tail wagging, and fighting with other males or even other anoles species.  James Stroud, a Ph.D. candidate from the Feeley lab @ Florida International University, presented on Saturday about the exploratory results of a new research method he and Robert Heathcote have started to construct social networks of A. sagrei and A. cristatellus in Miami, Florida. A. sagrei and A. cristatellus are similar in morphology and ecology and they wanted to learn how patterns of social interactions between these two species allow them to coexist outside of their native range.

Individual social behavior manifests itself collectively at the population level and interactions between populations (within and between species) might act as a basis for evolutionary processes. James and Robert tagged both male and female anoles in their study to track and recapture the animals in the future for a long term study. They measured the distance between every two anoles observed and inferred the strength of interaction as stronger if the anoles were closer to each other. Both species show a great web of interactions both within and between species. Some individuals are also much more “bold,” interacting with many males and females of either species, while others show fewer social interactions. These preliminary data are exciting since so little is known about Anolis social behavior. James also mentioned that they will be including additional data such as the types of interactions that will add great complexity and insight to this story.

Kristin Winchell, my fellow lab mate at the Revell lab, presented her work on the habitat use of two urban dwellers in Puerto Rico. Past studies have shown that Anolis cristatellus and Anolis stratulus vary in abundances and use different portions of the natural habitat. As early as 1964, Rand showed that A. stratulus was less abundant and perched higher on trees in forest habitat. However, we know very little about whether these patterns are maintained in urban areas where species have access to novel manmade structures. To address this, Kristin evaluated the habitat use of these two species across seven urban replicates and contrasted it to the available habitat. She found that urban A. stratulus uses more isolated perches with greater vegetative canopy and perches at higher portions of the habitat. Anolis cristatellus uses perches that are less isolated, shaded mostly by manmade canopy (i.e. buildings and houses) and at lower heights. When examining these patterns in a multidimensional space, she showed that A. cristatellus has expanded its urban niche through the use of manmade structures, while A. stratulus uses a subset of the natural portion of the habitat that A. cristatellus also uses.

Her research shows that these two urban dwellers interact with the novel portions of the habitat differently. Anolis cristellus has expanded its niche towards manmade structures which has implications for adaptation to enhance stability and locomotion when using these structures as shown in some of her previous work (Winchell, et al, 2016).  Anolis stratulus uses the less available remnants of the natural habitat which may have implication for conservation if they become sparser as urbanization expands.

Alexandra Herrera presented on using genetic population structure to understand how geographical processes have shaped genetic isolation of three widespread Anolis species on the Puerto Rican Bank. Geographical processes are an important event in shaping current populations and can lead to interesting patterns of diversification. However, these processes may not necessarily affect species similarly. In this study, Alexandra used a combination of nuclear genes and one mitochondrial gene to examine the population structure of these three anoles.

Evidence strongly suggests that populations of Anolis pulchellus were separated into two major clades through the formation of mountains. These two clades are made up of one cluster from south Puerto Rico and a cluster that includes both Northeast Puerto Rico and the Virgin Islands.

The diversification of the other two species corresponds with tectonic and sea level changes. For Anolis stratulus, divergence between populations in PR, Culebra, Vieques and the Virgins Islands occurred at the end of the Pliocene after the formation of the Virgin Passage.  These populations formed five clusters east PR, south PR, Virgin Islands, Vieques-Culebra and Peter-Norman islands.

For Anolis cristatellus the divergence between east PR and south PR with the Virgin Islands was estimated around the late Miocene-Pliocene transition when the Mona and Virgin Island passages formed. These populations formed 4 clusters east PR, south PR,  Virgin Islands and Carrot Rock-Peter-Culebra-Piñeiro.

This research shows that each species had a different diversification pattern and that they all occurred around the middle of late Pleistocene. Furthermore, geographical processes may affect species differently, leading to various patterns of population structures.

For many years, biologists believed that evolution was a process that played out over vast stretches of geological time and would not be observable during field studies. More recent research, however, has begun to show that evolution can occur very quickly and that experiments in the field can address evolution in action. Tom Schoener, eminent professor at the University of California, Davis, shed light on our evolving view of how evolution occurs in his talk, “Eco-evolutionary Aspects of the Lizard Anolis sagrei in an Island Metapopulation” at JMIH 2016.

By introducing a novel predator, the curly-tailed lizard (Leiocephalus carinatus), which devours anoles, to a series of small islands in the Bahamas, Schoener and colleagues were able to observe evolutionary responses in A. sagrei in fewer than 10 years. By preying on A. sagrei, curly-tailed lizards induced behavioral changes in perch height, and created selection for relatively longer limbs that increase anoles’ ability to escape this predator. Curly-tailed lizards also caused a variety of ecological effects, including reducing anole populations and changing arthropod abundance, which may affect the future evolution of anoles on these islands. Ongoing monitoring shows that these anole populations seem to be rebounding and that different types of selection may be acting on hindlimb length.

A curly-tailed lizard (Leiocephalus carinatus) displays its namesake in Florida. Photo by Ianaré Sévi.

Perhaps not surprisingly, many of the experimental islands were occasionally devastated by hurricanes which are becoming more frequent and more powerful in the Caribbean. While these extreme weather events interrupted some of Schoener’s planned research, they also provided a unique opportunity to study how hurricanes may cause natural selection. Schoener found that anoles which survived hurricanes had longer hindlimbs, and these lizards were better able to hold onto trees and other perches at high wind speeds, likely increasing survival of hurricanes by preventing lizards being blown out to sea! Taken together this body of research suggests that novel environmental changes, such as invasive species or increasingly extreme weather, exert selection on organisms and that we can observe these organisms evolving rapidly on ecological timescales.

Previous research in the Warner lab has shown that temperature during egg development influences fitness and performance in Anolis sagrei. In particular, a warmer incubation temperature increases sprint speed. The breeding season of A. sagrei spans from March through October, with lower temperatures early in the season and higher temperatures late in the season. Phil Pearson, a masters student in the Warner Lab, conducted an experiment to test whether embryos are developmentally adapted to their incubation temperature. He collected eggs from two temporally-separated cohorts and incubated them under two different temperatures, simulating seasonal temperature differences. He found that late season hatchlings had higher egg survival when incubated under late season temperature. Regardless of incubation temperature, late season embryos had higher sprint speed, larger body size and longer tails. This might compensate for the late start, since they are competing with early cohort individuals in the population.

Late season hatchlings have higher sprint speed regardless of incubation temperature

Overall, this suggests that timing of oviposition has greater effect on morphology and performance than incubation temperature. Future analysis will show whether timing of oviposition affects survival. Phil released the hatchlings on small islands to measure fitness using a mark-recapture approach and will hopefully present his findings at future meetings.

Figure 1. Anolis cupreus.

Spending two weeks searching for amphibians and reptiles along Nicaragua’s southern border proved very successful for a band of nature enthusiasts. Accompanied by my primatologist wife Barbara, fellow herpetologist, Joe Furman and his daughter Sadie, and our expert guide Lenin, we visited several nature reserves hoping to observe as many species of herps as possible. Our journey began in Ticuantepe, at the Montebelli Reserve, where we spent our first night searching the forest for any creatures that were out and about. The rainy season had not yet begun and the lack of rain resulted in a paucity of herpetological sightings. We did manage to find a few frogs (Smilisca baudinii and Scinax staufferi), a small fossorial snake (Enulius flavitorques), as well as a sleeping Copper Anole, Anolis cupreus (Fig. 1). Our stay here was brief and the following day we were on our way to the Ecological Center of Los Guatuzos, near the town of Papaturro.

Figure 2. Anolis limifrons.

The forests here were much more expansive and bordered the Papaturro River. and as a result the abundance of amphibians and reptiles was significantly greater. The river, which ran immediately in front of our accommodations, contained large numbers of Spectacled Caimans (Caiman crocodilus), ranging from yearling size to two meter long adults. At night their glowing orange eyes could clearly be seen scattered throughout the waterway like dim headlights on a busy thoroughfare. On our first night’s outing we observed more than a dozen species of amphibians and reptiles including the iconic Red-eyed Treefrog (Agalychnis callidryas), Fleischmann’s Glass Frog (Hyalinobatrachium fleischmanni) , the giant Smoky Jungle Frog (Leptodactylus pentadactylus), Clouded Snail-eating Snake (Sibon nebulatus), and two species of anoles: Slender (Anolis limifrons  Fig 2.), and the Neotropical Green Anole (Anolis biporcatus  Fig 3.).

Figure 3. Anolis biporcatus.

Figure 4. ???.

The following night we came upon an almost white-colored male anole (Fig. 4) sleeping on a leaf some two meters above the ground that we couldn’t readily identify. We realize that many anole species have different body color and patterns at night than they do during the day, so we decided to check the dewlap to see if that might help us render a positive identification. The dewlap was mostly light in coloration with several dark green spots scattered throughout (Fig. 5). Despite this characteristic coloration, the species remained unknown to us.

Figure 5. Dewlap of unidentified white anole in Fig. 4.

Figure 6. Second unidentified white anole.

Figure. 7 dewlap of second unidentified anole.

Shortly after finding this anole, another unidentified white anole was observed (Fig. 6) however, this one had a bright orange-colored dewlap (Fig. 7).

Our final destination took us up the Rio Bartola to the Reserva Naturale Indio Maiz. Like our previous sites this one had large, expansive forests with no other visitors anywhere in the vicinity. Fortunately, the rains had now begun and we were treated to a greater diversity of wildlife including more than two dozen species of amphibians and reptiles. Perhaps due to the onset of the rains or maybe because this reserve is naturally abundant in snake fauna, we ended up seeing more than a dozen serpents in just a few days time. Most notable among them was the seldom seen White-headed Snake, or Panda Bear Snake (Enuliophis sclateri  Fig 8), a small fossorial species known from only four other individuals from Nicaragua.

Figure 8 Enuliophis sclateri, White-headed Snake

Figure 9. Anolis capito

Six species of anoles were found here including the mossy-looking Anolis capito (Fig. 9), the Slender Anole (Anolis limifrons), the Lion Anole (Anolis lionotus  Fig. 10), of which several were observed during the day on rocks in a shallow stream as well as at night on thin branches overhanging the waterways, a species we were unfamiliar with but which our guide identified as Anolis  quaggulus (Fig 11).

Read More