A Failed Anole Predation Attempt

In the wake of the distressing news that even monkeys eat anoles with abandon, it’s a relief to see that there are at least some creatures that try to eat anoles, but fail. A 1979 report in The Wilson Bulletin by van Riper et al.  describing the the habits of the Red-Whiskered Bulbul in Hawaii, says this about these birds’ attempts at saurophagy:

On August 3rd 1977, a bulbul was observed chasing a large (ca. 20 cm in length) chamelion (Anolis sp.) in a circular pattern down an octopus tree; it was unsuccessful in capturing the reptile.

Such a vivid image, one that’s noteworthy for two reasons. First, while data on successful predation events are rare, descriptions of failed predation attempts are even rarer.  As bulbuls are mostly frugivorous, it isn’t too surprising that this lizard got away.

Second, like the battle between anoles and day geckos that we’re all eagerly anticipating, this interaction between two invasives, a New World lizard and an Old World bird, epitomizes the Anthropocene.

Red Whiskered Bulbul in southern India. Photo by adrashajoisa on Wikimedia.

Red Whiskered Bulbul in southern India. Photo by adrashajoisa on Wikimedia.

Carib Mountain High: Size, Elevation, and Convergent Evolution

In a recent paper in The American Naturalist, Martha Muñoz, Johanna Wegener, and Adam Algar noted an interesting pattern in two clades of Caribbean anoles evolving independently on Cuba and Hispaniola: high elevation species tended to have smaller body sizes than lower elevation species*.

Body Size - Elevation Relationships in Hispaniolan (cybotes clade) and Cuban (sagrei clade) anoles. The x-axis is elevation (on the log scale). The colors represent individual species within each clade.

Figure 1: Body size-elevation relationships in Hispaniolan (cybotes clade) and Cuban (sagrei clade) anoles. The x-axis is elevation in meters (on the log scale). The y-axis is SVL, or snout-vent length, a measure of size. The colors represent individual species within each clade; grey represents A. cybotes and A. sagrei on Hispaniola and Cuba, respectively.

Having found that the two groups converged independently on a similar evolutionary pattern, the authors wanted to know: was the underlying evolutionary progression also the same?

To answer this question, the authors took advantage of the fact that the two clades harbored multiple species. By measuring body size-elevation patterns within each species, and then asking how those patterns combined with interspecific patterns to create the overall body size-elevation cline (SEC) observed across all species, Muñoz & Co. could discern subtle differences between clades in the evolutionary trajectory towards convergence. For example, one clade might build its overall size-elevation cline by having the same SEC relationship present in each species, with species also sorting themselves by elevation and size (Model H1). Whereas another clade might build its size-elevation cline just through interspecific differences in size and elevation, without an SEC relationship within species (Model H2).

Figure 2: Two models, of eight that the authors proposed, which might explain how body size-elevation clines evolve. Within-species clines are represented by different colored/dashed lines. Across-species clines are best visualized by drawing an imaginary line through average size and elevation of each species . In H1, each species has the same size-elevation relationship (i.e., the negative slope) and is found at different elevations. This creates a size-elevation relationship that depends on both intra- and interspecific patterns. In H2, each species has no size-elevation relationship (i.e., the flat slope) but is found at different elevations. Here, the size-elevation relationship is driven purely by interspecific differences in elevation and size.

The authors developed eight models for how elevation and size might be related within species and across species. They tested which of those eight models best explained variation in the relationship between size and elevation within species and clades, while accounting for spatial autocorrelation among collection localities and differences in elevational range among species . They then compared best models across clades to see whether convergence was reached by similar or different evolutionary pathways.

What did they find?

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Figure 3: Intra-specific size-elevation clines (SECs) for Hispaniola (left panel) and Cuba (right panel). Solid lines represent significant SECs; dashed lines represent non-significant SECs.

On Hispaniola, each species tended not to show any significant intraspecific SEC relationships: note the flat slopes of the dashed lines in the left panel of Figure 3. Instead, much of the overall SEC comes from interspecific differences in size and elevation, consistent with Model H2 (Figure 2).

On Cuba, in contrast, the authors found some significant within-species SEC relationships–the solid lines in the right panel of Figure 3–but found that interspecific differences in size and elevation explained very little of the clade’s overall SEC (Figure 4)**.

The model most consistent with the Cuban data.

The model most consistent with the Cuban data.

Thus the authors answered their question: “Although the precise mechanisms underlying inverse size[-elevation] clines remains  unknown, it is clear that they were constructed in different ways on Cuba and Hispaniola.” In other words, the two clades show a pattern of convergence to small size, but they took different routes of intra- and interspecific evolution to get there. It reminds me of Yogi Berra’s response when asked directions to his house: “When you get to the fork in the road, take it!”

 

CITATION: M.M. Munoz, J.E. Wegener, and A.C. Algar. 2014. Untangling Intra- and Interspecific Effects on Body Size Clines Reveals Divergent Processes Structuring Convergent Patterns in Anolis lizards. The American Naturalist 184: 636-646.

 

* This pattern was measured from 16 Anolis species: nine in the sagrei clade (Cuba) and seven in the cybotes clade (Hispaniola). The finding of small body size at high elevations is the inverse expectation of Bergmann’s rule. Bergmann’s rule, as originally conceived, states that endothermic species living in colder climates should be larger (or have a larger surface area to volume ratio), all else equal, to conserve heat. As lizards are ectothermic, one would expect an inverse Bergmann. Perhaps we could call the inverse cline Nnamgerb’s rule? It does have a certain charm to it, no?

** I wonder if the authors might chime in in the comments section. What does it mean that a size-elevation cline wasn’t found on Cuba when using the mean size and elevation of each population (Fig 5 below), but it was found when species identity was ignored (Fig 1 above)? Is this an example of Simpson’s paradox?

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Puerto Rican Giant Green Anole Mating

 

Anolis cuvieri. Photo by Alejandro Sanchez.

Anolis cuvieri. Photo by Alejandro Sanchez.

Photo by Alejandro Sanchez.

Photo by Alejandro Sanchez.

Father Alejandro Sanchez has done it again! Previously, he posted some wonderful photos of Anolis cuvieri moving around, now he’s caught them in flagrante delicto. Here’s the backstory: “The pics were taken around 10:30 AM. The lizards were about 10 meters above ground. I cannot take credit for the initial sighting. The group of students of UPR-Humacao saw the male jump to the tree where the female was and almost immediately copulation started. In all it lasted about 15 minutes. The separation was very abrupt (possibly caused by the group of people under the tree, taking pictures). At that point the male jumped to another branch and ran down low enough for me to be able to shake it down and capture it. At that time, the male still had his hemipenis everted.”

Monkeys Eat Anoles

Capuchin monkey eating a basilisk. Photo by Andrew G.

Capuchin monkeys may look cute, but in reality they’re cold-blooded killers. A recent paper in Herpetology Notes reports on a golden-bellied capuchin (different species than the one pictured above and below) that ate a Polychrus marmoratus, an Anolis ortonii, and an Enyalius catenatus.

Monkey predation on anoles has been documented previously. This paper cites a case of a capuchin eating an A. cupreus, and primatologist Betsy Mitchell recorded one eating an anole–perhaps A. frenatus–in her thesis (which I don’t have in front of me). We also reported on another capuchin species eating a Polychrus in a previous post. A quick google found an undocumented report of rhesus macaques eating A. carolinensis in Florida. Anyone know of any other reports?

And, finally, for your delectation, a video of a capuchin eating an iguana:

Turn the Clock Back Anole Style: 50% Off Ecomorph Watches Today

watches

The Ecomorph Line of of watches is half off today at Zazzle.com. Check ’em out, and use the code SUNDAYDEAL59.

Knight Anoles Spreading through Florida

An iguanito. Photo from the Coastal Star.

A nice article in the Coastal Star just reported on the spread of knight anoles through Florida. The article contains numerous nuggets, such as quotes from the Florida Fish and Wildlife Commission stating that they’re worried about bigger things (e.g., pythons, tegus), that they’re locally called “iguanitos,” and that iguanas are rebounding from freeze-caused mortality in the recent past and are mainly a problem for pooping by people’s pools.

Anolis huilae en Cacería (Anolis huilae Hunting)

Macho de Anolis huilae acechando su presa.

Macho de Anolis huilae acechando una presa.

Observaciones realizadas en mi finca (Ibagué – Colombia) de un macho de Anolis huilae acechando su presa y una hembra predando su presa. He tenido la oportunidad de observar individuos de ésta especie cazando orugas, larvas y moscas y, la manera como ellos invierten algún tiempo para acechar a sus presas para capturarlas . Aún se desconoce la dieta exacta de esta especie de lagarto endémico de la cordillera Central de Colombia.

Predación por parte de Anolis huilae

Predación por parte de una hembra de Anolis huilae

Editor’s note: Google translates the passage above as follows. It’s amazing how good this programs are getting!:

Observations made on my farm (Ibague - Colombia) of a male Anolis huilae stalking his prey and a female predating its prey. I have had the opportunity to observe individuals of this species hunting caterpillars, larvae and flies and how they spend some time to stalk their prey to catch them. The exact diet of this species of lizard endemic to Central Cordillera of Colombia is still unknown.

Battle of the Lilliputian Brown Anoles

Championship round, lightweight division. Photo from Daffodil’s Photo Blog.

We periodically post pictures, videos and stories of male anoles duking it out with each other [e.g., 1,2], but over on Daffodil’s Photo Blog is evidence that such squabbling starts at a young age. Check out how the little fellas, with barely a dewlap to speak of, nonetheless behave just the same as their elders.

Creationists on Lizard Evolution Study: “What’s the Big Deal?”

discovery institute

Last week, Yoel Stuart and colleagues (including me) published a paper demonstrating that green anoles had rapidly (ca. 20 years) evolved an increase in toepad size as a result of upward shifts in habitat use caused the presence of brown anoles.

The Discovery Institute, an organization devoted to the advocacy of creationist views, posted a blog yesterday saying, basically, “this is not news?” After summarizing the study, here’s what they have to say:

“….these scientists found that when a new species of lizards invaded another’s territory (in fact the new species was placed there intentionally by the researchers, meaning they weren’t quite studying “natural” selection), the old one sought higher ground. That seems like a smart thing to do. To go along with the new territory, they subsequently evolved “larger toepads (see here for a picture).

After reading this, what I really wanted to see was the precise sizes of the toepad and compare the changes. But alas that information is not in the paper. I tried downloading the supplemental materials but it’s not there either. So let’s assume that the toepad size changed a lot. What have we shown?

Not much. We’ve seen that the size of lizard feet can change in response to invaders’ driving a species to perch at higher levels in the trees. No new traits arose. Only the size of a pre-existing trait changed. Again, that’s interesting but such changes in the size of lizard feet do very little to explain the origin of lizards in the first place, even if these changes happen in just a few generations.

If we take seriously the statement from the authors that the modest results from this study can help test “evolutionary hypotheses about phenomena … on time scales too long for direct observation,” then that implies that over long periods you might be able to change the size of an organism or some of its body parts. Since when is that news?”

The Blue-Dewlapped Anole of Grand Cayman

 

conspersus displayingNot many anoles have blue dewlaps, so we were delighted to see Ann Stafford’s tweet of this lovely  conspersus from Grand Cayman strutting its stuff.

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