Anolis heterodermus. Photo from iNaturalist by Andres Florez.

Although anoles are much more well studied and understood in the Caribbean and United States, there is a decent amount of diversity of these lizards throughout South America as well. In consultation with Jonathan Losos, I have agreed to write a series of posts outlining the South American diversity (parts 1 and 2), invasives (part 3), and conservation (part 4) of these animals. This post (diversity part 1) will describe the species that occur in the regions of South America north and west of the Andes along the Caribbean and Pacific Coasts, respectively, while diversity part 2 will focus on the Amazon and everything south and east of the Amazon.

In case you don’t know me, I had experience as a graduate student studying lizard functional morphology of toes and tails in North, Central, and South America. More recently, I have become way too involved in identifying lizards on iNaturalist.org, with a focus on lizards of the New World. To satisfy my own particular obsessiveness, I have tried to identify every lizard observed in the Amazon (all 300+ species of them!) and have expanded those lizard-identifying efforts into other areas as well. It was these efforts that gave me the idea that perhaps the AnoleAnnals might be interested in what I’ve noticed from this relatively understudied part of the world. As such, I will draw liberally from data available on iNaturalist to illustrate my points.

Anole diversity along Caribbean and Pacific Coasts

As of this writing, there are currently nearly 12,000 observations on iNaturalist of 102 species Anolis in South America (“research grade” observations filtered by “wild” and “has photos”). Compare this to the 238,000 observations of 270 species from North America (on iNat this region includes all of Central America, Mexico, the United States, and the Caribbean). Only eight of the species of South American anoles are introduced non-native species (more on this in part 3). This suggests that there are nearly 100 species of Anolis endemic to South America. Clearly, the anoles from South America are not as diverse and not as well observed as those from other areas.

Anoles along the Pacific Coast range from southern Ecuador (and perhaps northern Peru, but not well documented) north to the junction with Central America and continue along the Caribbean Coast east to the mouth of the Orinoco River in Venezuela (note: according to iNaturalist, Guyana, Suriname, and French Guiana are part of the Amazon region even though they may not be part of the Amazon watershed). This region is separated from the Amazon by the Andes Mountains and Orinoco River and very few species cross these particular barriers. Hence, many of the anoles of northern South America still have some degree of endemism and it is this endemism (and the resulting beta diversity) that I highlight below. Keep in mind that new species are being described on a regular basis, so the list below is almost certainly incomplete, but still illustrates my general point.

The species of Anolis that occur in north and west of the Andes include (organized by their geographic distribution):

Western (non-Amazonian) Ecuador (n=9)

A. bionotatus, A. bitectus, A. fasciatus, A. festae, A. lyra, A. neomonteae, A. parilis, A. peraccae, A. proboscis

Western (non-Amazonian) Colombia (n=18)

A. anchicayae, A. antioquiae, A. antonii, A. calimae, A. danieli, A. eulaemus, A. gorgonae, A. heterodermus, A. maculigula, A. macrolepis, A. mariarum, A. medemi, A. quimbaya, A. solitarius, A. sulcifrons, A. tolimensis, A. urraoi, A. ventrimaculatus

Western Ecuador/Colombia (n=13)

A. aequatorialis, A. anchicayae, A. chloris, A. dracula, A. fraseri, A. gemmosus, A. gracilipes, A. granuliceps, A. limon, A. lynchi, A. maculiventris, A. parvauritus, A. princeps

Northern Colombia/Venezuela (n=3)

A. jacare, A. onca, A. tetarii

Northern Venezuela (n=4)

A. anatoloros, A. annectans, A. squamulatus, A. tigrinus

Aruba, Bonaire, and/or Curaçao (A-B-C islands) (n=2)

A. bonairensis, A. lineatus

Found in western Colombia as well as crossing the Darién Gap into Central America (n=8)

A. biporcatus, A. gaigei, A. latifrons, A. poecilopus, A. purpurescens, A. triumphalis, A. tropidogaster, A. vittigerus

Along Caribbean Coast as well as crossing into the Amazon (n=2)

A. auratus, A. planiceps

Non-native anoles (n=8)

A. aeneus, A. cristatellus, A. marmoratus, A. porcatus, A. richardii, A. sagrei, A. trinitatis, A. wattsii

Several things become apparent when considering the above diversity.

—First, there are roughly 67 species of anoles that occur north of the Amazon. Given that there are only about 102 anole species that occur in all of South America, perhaps 2/3 occur in the area adjacent to the speciose Caribbean. That leaves only 1/3 of the South American anole species occurring south and east of the Andes Mountains.

—Second, of the 67 anole species found north of the Amazon, 47 species (70%) are endemic to this region of mainland South America, two species (3%) are endemic to the A-B-C islands, eight species (12%) cross from mainland South America into Central America, and two species (3%) are found extensively in the Amazon as well. So, not as diverse as North America, but with outstanding regional endemism. This regional endemism translates into an impressive beta diversity with geographic replacement probably the rule rather than the exception. In other words, when travelling from one valley to the next, species replacement (beta diversity) occurs at a relatively high rate so that nearly an entirely different set of species may be present in adjacent areas, depending on the nature of the barrier between them. Making this even more of a challenge, in some instances the barrier appears to be the low-lying valley instead of a mountain ridge. For example, in Colombia, Anolis heterodermus Duméril 1851 was recently split into eight distinct species (Morena-Arias et al. 2023). Both the various mountain ranges (Cordillera) as well as the Magdalena River valley appear to act as barriers isolating the various lineages into distinct species. Hence, in terms of trying to identify the Anolis in some of these areas, accurate geographic location is a must.

—Third, there are only eight species (12%) of non-native anoles in all of South America (including the A-B-C islands and Trinidad and Tobago). All eight occur in northern South America and only one or two (A. porcatus and perhaps A. sagrei) occur elsewhere in South America. Contrast this with the 16 or so species of introduced anoles in North America, which have made extensive inroads in places like the southeastern United States, southern Mexico, and certain of the Caribbean Islands. These eight introduced species will be the focus on part 3 of this series.

One of the interesting things about the high degree of endemism of the anoles of northern South America is how quickly it probably occurred. Andean orogeny began perhaps 20 million years ago (mya) and lasted until about 8 mya. Hence, the diversity differences between the occidental (western) and oriental (eastern) regions of countries such as Ecuador, Colombia, and Venezuela are notable for their near completeness. For comparison, the Laramide orogeny that created the Rocky Mountains occurred between 80-55 mya; the Alleghanian orogeny that created the Appalachian Mountains occurred between 325-260 mya. Hence, the temporal arrival of the Andes created spatial barriers to gene flow and geographic complexity that is reflected in the high beta diversity of Anolis both within and between regions of South America.

In conclusion, northern South America is the diversity hotspot for anoles. The anole species north of the Amazon are dominated by native, highly endemic species that often have geographic ranges limited to a single country, a single valley, or even one slope of a single mountain ridge. Moreover, there are relatively few introduced anoles in South America with most of those introduced to the A-B-C islands and Trinidad and Tobago. Given that almost no species of anoles cross the Orinoco River or Andes Mountains and very few species occur extensively in the Carribean or Central America, the anoles of northern South America represent a fairly separate and distinct fauna when compared to other geographic regions within the distribution of Anolis.

 

Literature cited:

Moreno-Arias, R. A., Méndez-Galeano, M. A., Beltrán, I., & Vargas-Ramírez, M. 2023. Revealing anole diversity in the highlands of the Northern Andes: New and resurrected species of the Anolis heterodermus species group. Vertebrate Zoology, 73, 161-188

Pete Zani
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