Author: Yoel Stuart

I am interested in whether, how, and why ecology shapes evolution (and evolution shapes ecology) through time, with an emphasis on microevolutionary pattern and process, adaptation, and field experiments. I completed my Ph.D. on Anolis lizards in the Department of Organismic and Evolutionary Biology at Harvard University. I am currently a post-doctoral researcher at the University of Texas, Austin studying threespine stickleback. They're not anoles, but they're cool too.

The Anoles of Mérida

By Yoel Stuart

On December 13, 2010

In Anole Art, Literature, and Humor

“It must be the oldest part of Mérida…. In the afternoon when the sun lights the stucco buildings across the street, it’s possible to count a dozen different colors of paint, all fading together on the highest part of the wall…. Cats stalk lizards among the clay pots around the fountain, doves settle into the flowering vines and coo their prayers, thankful for the existence of lizards.” – The Lacuna, a novel by B. Kingsolver (2009; Harper Perennial; pp.393)

Mérida is the capital city of the Mexican state of Yúcatan. Of the lizards alluded to in the passage above, some were undoubtedly anoles. Anoles are well known for their radiation in the Caribbean but are less appreciated for their radiations in mainland Central and South America, which rival their Caribbean counterpart in species diversity and morphological disparity.

(I say radiations because there were actually two radiations on the mainland. The first mainland radiation includes the basal clade of Anolis and is paraphyletic because the Caribbean radiation arose from within it. The second radiation, monophyletic, is actually a back-colonization of the mainland from the Caribbean.)

Which mainland anoles could be in Mérida? There are five anoles whose species distribution places them near or in Mérida: Anolis sagrei, A. lemurinus, A. tropidonotus, A. rogdriguezii, and A. sericeus. We’ll explore the natural history of these species to determine for which one(s) Mérida’s doves are thankful.

(1) Anolis sagrei, the brown anole, is not actually a mainland anole. This Cuban species is well known for its invasive abilities. For example, it has invaded the southeast U.S., Jamaica, Central America, Hawaii, and even Taiwan. Cats are known to feast on Anolis sagrei in other parts of its range, and there is a record of A. sagrei in Mérida; however, because The Lacuna is set in the early 1950s, we will assume that A. sagrei had not yet arrived in Mérida to fall prey to cats.

Anolis sagrei - photo by Neil Losin (http://www.daysedgeproductions.com/neil.blog/)

(2) Anolis lemurinus is a grey-colored anole, found in the understory of lowland forests. Individuals of this species are partial to shaded habitats and perch on the buttresses of trees while they watch and wait for their invertebrate prey. Often, they are heard scampering along the forest floor before they are seen. Perhaps this is why this species is called lemurinus, which means “belonging to the ghosts of the dead” in Latin. Anolis lemurinus is probably not food for Mérida’s cats for two reasons: (1) Mérida lies just beyond the edge of the species range for A. lemurinus, and (2) A. lemurinus is a forest, not city, dweller.

Anolis lemurinus - photo by Michael Benard http://calphotos.berkeley.edu/cgi/img_query?enlarge=0000+0000+0107+1742

(3) Anolis tropidonotus lives in primary and secondary forests. It too is a forest dwelling anole, preferring shady habitats. Individuals in this species are predominantly terrestrial and will burrow into the leaf litter to escape capture. Like A. lemurinus, A. tropidonotus is primarily a forest species and its range nears but does not include Mérida. Thus, it is an unlikely candidate.

Anolis tropidonotus - photo by Josiah Townsend http://www.flickr.com/photos/24831531@N07/2353154759/

(4) Anolis rodriguezii is a small anole that can be found most often in dry forests but in other forest types too. It usually perches several meters high but is known to descend out of the canopy to the ground. It also scrambles along the walls of ancient Mayan ruins. There is record of this species from Mérida, so it is probably common in the forests around Mérida, may venture into human establishments, and could be falling prey to cats in Mérida

(5) Anolis sericeus is a small anole too. This species prefers open savanna habitats, forest edges, and areas disturbed by human activity. Individuals in this species perch on shrubs, bushes, and grass tufts. Males of this lizard have a striking dewlap that is yellow with a blue or purple spot in the center. Given this species’s penchant for human-impacted environments and its near-ground perching habits, A. sericeus seems the mostly likely anole candidate to be cat food in Mérida.

A. sericeus - http://www.fororeptiles.org/galerias/images/88/large/1_anolis_sericeus.JPG

A haiku from the doves in homage to A. sericeus:

Coo-rageous anole,
Anolis sericeus.
Distracts pesky cats.

Many thanks to Julian C. Lee. I collected most of the information about the anoles of Mérida from his two books: The amphibians and reptiles of the Yucatan Peninsula (1996 – Comstock Publishing) and A field guide to the amphibians and reptiles of the Maya world (2000 – Cornell University Press).

Where’s Anoldo?

By Yoel Stuart

On December 7, 2010

In New Research

Imagine you’re walking down a busy city street, talking with your friend about the latest post you read on Anole Annals. You’re getting to the most exciting part of the discussion when a bus rumbles by and drowns out your sentences. Your friend can’t hear you and loses out on amazing anole knowledge.

Animals that live in complicated environments with noisy backgrounds face similar communication challenges. The signal can be auditory – imagine a frog trying to find a mate in a multispecies chorus in a Costa Rican swamp that just received its first rain of the year. The signal can be olfactory – imagine an ant trying to follow an hour-old trail laid down by one of its sisters. The noise can be visual too – imagine a transparent jellyfish trying to find a mate in the poor light environment of the ocean.

Or, Waldo trying to find Wenda.

Tough, right?

To ensure that communication is successful, animals should evolve signals that are highly conspicuous in the environment in which those signals are used.

Anoles are well known for their charismatic displays. They do push-ups, bob their heads, and extend a colorful flap of skin beneath their chin called a dewlap. Anoles display during territorial conflicts, courtship behavior, and predator avoidance. Anoles tend to live in very noisy environments. For example, how is a male anole displaying in the low-light forest understory to be seen against a background of shaking leaves?

One way for an anole to be seen is to create a dewlap whose color has great contrast in the light environment in which it is usually found. Another way is to use a display with jerky movements and rapid dewlap extensions that stands out even against low light and shaking leaves (Ord and Stamps 2008). A third way to be seen, discussed in a new paper by Ord et al. (2010), is to time displays to run during periods in which background noise is relatively low (i.e. the wind dies down and the leaves stop shaking). Imagine pausing your city-street conversation of anoles until after the bus had passed.

Ord et al. test whether anoles match their displays to calm backgrounds by comparing the display timing of Jamaican anoles, which use a rapid, jerky display, to Puerto Rican anoles, which use a slow, drawn out display. They hypothesize that the Puerto Rican species, with their slower head bobs and dewlap extensions, will time their displays to match a quiet background. In contrast, Jamaican species, whose display is thought to be suitable in noisy visual conditions, should show less background matching (Ord and Stamps 2008).

To answer this question, Ord et al. analyzed videos of lizard displays, comparing background noise during lizard displays to similar stretches of time when lizards were not displaying. They compared four species on Jamaica to four species on Puerto Rico. The species were similar in habitat use and dewlap color between islands, and there were no appreciable differences in the physical environment between islands.

Consistent with their hypothesis, Ord et al. found that Puerto Rican species actively avoided displaying during periods of high environmental noise; they waited until until the visual background calmed down. In contrast, Jamaican lizards did not time their displays as carefully. Thus, it appears that these two lineages of Anolis lizards have evolved different strategies to solve the problem of how to communicate in noisy visual environments.

Puerto Rican anoles avoid displaying during periods of high noise.

The Dorsal Crest

By Yoel Stuart

On November 22, 2010

In Notes from the Field

Photo by Casey Gilman, U. Mass. Amherst

In addition to performing dewlap extensions, head bobs, and pushups, many anoles raise a dorsal crest during territorial disputes. Here, two Anolis sagrei males square off. The static dorsal crest serves to modify the appearance of active pushups and dewlap extensions, perhaps making the male appear larger and more imposing. It is unclear how the crest is controlled. Jenssen notes the lag period before the crest is raised and the persistence of the crest after a territorial bout is concluded; thus, the crest may be a response to adrenaline and under the control of the sympathetic nervous system. Note the tongue extension by the top lizard.

Anolis Predation

By Yoel Stuart

On November 15, 2010

In Notes from the Field

Anoles fall prey to a variety of animals. Here, a male brown anole, A. sagrei, is being subdued and swallowed by a black racer (Coluber constrictor). Casey Gilman and I heard the two animals struggling while working on spoils islands in Mosquito Lagoon.

Photo by C. Gilman, U. Mass. Amherst

All of these islands have Florida-native green anoles (Anolis carolinensis) on them. Most islands also have the brown anole, an invasive species. In his Anolis Newsletter VI contribution, Nathan Turnbough found a non-random association between brown anole presence and racer presence on Mosquito Lagoon islands. He concluded that high densities of brown anoles support more racers.

Green anoles tend to become more arboreal in the presence of brown anoles. It is generally thought that direct interactions between the species, like resource competition or intraguild predation, cause this habitat shift. However, by increasing the density of predators, brown anoles may also indirectly affect green anole habitat use. The habitat shift may result from green anoles getting out of the way of ground-foraging racers – an escape to enemy free space.