Anolis phyllorhinus. [Photo from iNaturalist by Christopher Borges](https://www.inaturalist.org/observations/145912245)
In a earlier publish, I reviewed the range of Anolis lizards north of the Andes in South America. On this publish I proceed on that theme with a assessment of the range of anoles within the Amazon and south of the Amazon all through South America. A lot of this assessment should embody the caveat that this understanding is ever-changing as new taxa are described.
I begin with an inventory of native anoles south of the Andes in South America, which is a surprisingly quick listing contemplating the big space included and that this listing additionally consists of the Amazon basin.
Widespread all through each Amazon and Atlantic rainforests
A. punctatus, A. fuscoauratus, A. ortonii
Widespread, however restricted to the Amazon
A. trachyderma, A. transversalis, A. chrysolepis, A. tandai, A. bombiceps
Happens in Amazon and/or llanos northwest of Amazon
A. scypheus, A. inderenae, A. vanzolinii, A. huilae, A. ruizii
Restricted distribution in northern llanos/Amazon and north of Andes
A. planiceps, A. auratus
Vary restricted in western and southwestern Amazon
A. phyllorhinus, A. cuscoensis, A. dissimilis, A. lososi, A. boettgeri, A. soinii, A. fitchi, A. podocarpus, A. orcesi
Widespread in sub-Amazonian (southeastern) dry forests of South America
A. meridionalis, A. brasiliensis
Restricted distribution in sub-Amazonian (southeastern) Atlantic rainforests of South America
A. nasofrontalis, A. pseudotigrinus. A. neglectus
There are roughly 102 anole species that happen in all of South America. Nonetheless, 67 or so of those happen north and west of the Andes (the so-called trans-Andean area) leaving maybe 35-40 species south of the Andes (cis-Andean). The numbers don’t fairly add up as a result of a small handful of species (e.g., A. planiceps, A. auratus) happen in each areas relying on how these areas are outlined geographically. So, regardless of the nice variety of anoles within the Caribbean and Central America, and even the respectable variety of anoles north of the Andes, the cis-Andean area is comparatively variety poor. Causes for this lack of cis-Andean anole variety consists of the shortage of significant geographic limitations which will make speciation much less frequent in anoles. Alternatively, these animals are much less generally used as research topics so delicate molecular variety might not but have been recognized in these lineages. Both means, regardless of occurring all through the Amazon basin, the llanos of Colombia and Venezuela to the northwest of the Amazon, the dry transitional forests and grasslands of Brazil to the southeast of the Amazon, in addition to within the coastal rainforests of Brazil alongside the Atlantic coast, solely a number of dozens of species of anoles occurn south of the Andes mountains, a lot of that are vary restricted in a couple of small areas up in opposition to the mountains themselves.
A lot of the anoles on this space of South America are discovered within the Amazon area, which is sensible given the huge extent of the rainforest ecosystem within the northern half of the continent. Regardless of this, there are presently solely 28 or so species of anoles in your entire Amazon noticed on iNaturalist.org, all however three of that are thought of native (non-introduced) species. Over half of those species (16 or so) are endemic to the Amazon area (broadly outlined) and located nowhere else [note, in this context, I use iNaturalist’s definition of “Amazon region” which includes the dry edges [llanos in the northwest, cerrado in the southeast] and never simply the rainforest ecosystem correct, together with extending all the way in which to the Orinoco within the north). So, clearly the Amazon is the middle of variety for cis-Andean anoles even because the variety of species (25 or so native species) is just not particularly spectacular provided that there are presently over 300 species of lizards described from the Amazon. Maybe it’s this lizard variety itself that accounts for the shortage of species richness in anoles in that most of the niches occupied by anoles elsewhere (e.g., crown giants) are seemingly occupied by competing species (e.g. Tropiduridae, Polychrotidae). Or if not opponents, maybe the nice variety of predators is what accounts for the shortage of anole variety (iNaturalist presently consists of observations of over 300 species of snakes within the Amazon alone). Both means, anoles are clearly not the dominant taxon south of the Andes that they seem like elsewhere. Nonetheless, they do nonetheless happen almost all over the place in South America.
The pure distribution of anoles in South America reaches south to concerning the latitude of São Paulo (23.6°S), or simply outdoors the Tropic of Capricorn. This corresponds roughly to the latitude of Miami simply outdoors the Tropic of Most cancers within the northern hemisphere. Nonetheless, the native Anolis carolinensis within the north has a pure vary at increased latitudes, suggesting the southern extent of the anole radiation is just not as nice as it’s within the north. As with that northern vary margin for the clade, the range of anoles dwindles drastically alongside the Atlantic coast close to the vary edges with solely maybe one native species occurring south of Rio de Janeiro (22.9°S) (Anolis porcatus is launched in São Paulo, however launched species can be mentioned in a future publish). Even inland, there’s solely maybe one species of anole that ranges as far south as Paraguay or far northern Argentina. So, despite the fact that widespread, the sample of variety is such that anoles seem much less widespread in southern hemisphere than within the northern hemisphere.
Maybe, one of many extra attention-grabbing patterns to emerge when contemplating anole variety in South America is the sluggish, however regular description of recent species, a lot of that are vary restricted to small areas within the southern and western elements of the Amazon. The best variety of species within the Amazon could be described as vary restricted with maybe 9 species occurring in small native enclaves or areas. These embody a few of the extra enigmatic species similar to Anolis phyllorhinus with the lengthy fleshy proboscis within the males. Thus, as with the trans-Andean anoles, the geographic complexity of the Andes has seemingly created circumstances for some model of allopatric species to happen, whether or not or not it’s true allopatry or some sort of peripatry on a variety’s periphery. I absolutely count on that further species can be described from the Andean foothills or the western and southwestern Amazon.
Lastly, it’s attention-grabbing to think about the close to full substitute of species on both aspect of the Andes with little or no crossover; clearly the Andes are a reasonably efficient barrier to gene movement for anoles. Just a few species seem to happen on each aspect of the Andes within the space south and east of Bogotá, Colombia. Nonetheless, this crossover seems to be restricted by way of variety and extent of species. As a substitute, the most important trade of species seems to have occurred across the northern terminus of the Andes in Venezuela the place two species specifically span the cis- and trans-Andean areas: Anolis planiceps and A. auratus. Anolis planiceps happens alongside the Caribbean coast of Venezuela in addition to south into Colombia, Guyana, and Roraima, Brazil. Nonetheless, Anolis auratus as presently outlined happens way more broadly starting from Costa Rica and Panama, all through cis- and trans-Andean areas of Colombia and Venezuela, alongside the Atlantic coast to at the least Amapá, Brazil, and south into the states of Roraima and Pará, Brazil. In Brazil specifically A. auratus appears to be restricted to areas of geologic uplift which have created the grassland habitat with which this species is related. The highlands to the north and south of the Amazon river had been created when the Guiana Protect and Brazilian Protect, respectively, had been pressured upward by geologic uplifting. Therefore, the Amazon river roughly runs within the low areas in-between the uplift of those two giant blocks on the South American continent. Simply south of the Amazon River, an remoted inhabitants of Anolis auratus happens in a spot referred to as Alter do Chão (translation from Portuguese is actually ‘altar of floor’) the place a small piece of the raised uplift creates savanna-like grassland/forest habitat surrounded by lowland Amazon rainforest to the south and east and bordered by the Amazon and Tapajós Rivers to the north and west, respectively. The presence of those lizards in as a small and remoted enclave 1000 km from their nearest neighbors generates extra questions than solutions. How lengthy have they been there? How did they get there? How distinct are they? How steady is that this inhabitants? These are all good and unresolved questions remaining to be addressed biologically.
I saved the above commentary for final to make the purpose that on the floor the Amazon might seem like an unlimited tract of uniform habitat with little limitations to gene movement resulting in organic uniformity, however the actuality is that this view is overly simplistic within the context of how species are literally distributed on the panorama. Somewhat, it’s seemingly the shortage of obtainable information that forestall us from really understanding the biogeography of lizards within the Amazon and different areas of South America. This makes the continuous addition of recent species and biogeographic patterns helpful and thrilling given the advances in molecular biology that proceed to additional our understanding. Therefore, even within the comparatively anole-poor areas of South America, anoles proceed as a mannequin system for understanding patterns of organic variety.
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