The Western Amazonian Richness Gradient for Squamate Reptiles: Are There Really Fewer Snakes and Lizards in Southwestern Amazonian Lowlands?

Abstract

The lowland rainforests of the Amazon basin harbor some of the most species-rich reptile communities on Earth. However, there is considerable heterogeneity among climatically-similar sites across the Amazon basin, and faunal surveys for southwestern Amazonia in particular have revealed lower species diversity relative to sites in the northwestern and central Amazon. Here, we report a herpetofaunal inventory for Los Amigos Biological Station (LABS), a lowland site located in the Madre de Dios watershed of southern Peru. By combining active search and passive trapping methods with prior records for the site, we provide a comprehensive species list for squamate reptiles from LABS. We also estimate an “expected” list for LABS by tabulating additional taxa known from the regional species pool that we consider to have a high probability of detection with further sampling. The LABS total of 60 snake and 26 lizard taxa is perhaps the highest for any single site in the southern Amazon. Our estimate of the regional species pool for LABS suggests that the southwestern Amazonian lowlands harbor at least 25% fewer species of snakes relative to the western equatorial Amazon, a diversity reduction that is consistent with patterns observed in several other taxonomic groups. We discuss potential causes of this western Amazonian richness gradient and comment on the relationship between spatial diversity patterns in squamates and other taxa in the Amazon basin.

Uncovering hidden species diversity of alopoglossid lizards in Amazonia, with the description of three new species ofAlopoglossus(Squamata: Gymnophthalmoidae)

“…Amazonia is characterized by some of the highest species richness of reptiles Squamata on Earth (Gumbs et al, 2020;Rabosky et al, 2019;Roll et al, 2017), and its diversity is heterogeneously distributed across this region (Ribeiro-Júnior & Amaral, 2016b). In Brazilian Amazonia, high lizard richness were recorded along the lower courses of Trombetas, Negro and Japurá rivers, the middle courses of Tapajós and Madeira rivers, and the upper courses of Juruá, Madeira and Amazon rivers (Ribeiro-Júnior & Amaral, 2016b).…”

“…Species delimitation analyses applied to the mtDNA variation were conducted considering the best sampled locus in our dataset (ND4, 52/61 individuals, 638 bp). We applied a distance-based method Approximate Barcode Gap Discovery (ABGD; Puillandre et al, 2012), using an online server (https://bioin fo.mnhn.fr/abi/ publi c/abgd/abgdw eb.html), and a tree-based method Generalized Mixed Yule Coalescent with multiple threshold (GMYC ;Fujisawa & Barraclough, 2013). For the ABGD delimitation, we used the Jukes-Cantor (JC) genetic distance correction, a prior of intraspecific divergence (P) between 0.001 and 0.1, a proxy for minimum relative gap width (X) of 0.5, and 30 steps (n = 30).…”

“…For the ABGD delimitation, we used the Jukes-Cantor (JC) genetic distance correction, a prior of intraspecific divergence (P) between 0.001 and 0.1, a proxy for minimum relative gap width (X) of 0.5, and 30 steps (n = 30). Based on an intraspecific divergence of 1% (arbitrary threshold recognized in vertebrate delimitation) and the end of a plateau for group number (Puillandre et al, 2012), we kept the 17th partition (p = 0.0127) to delimit the species. For the GMYC delimitation, we firstly reconstructed a timecalibrated ultrametric tree using the software BEAST 2.6 (Bouckaert et al, 2014), using the same nucleotide substitution models detailed for the complete phylogenetic inferences, an uncorrelated relaxed clock lognormal and a Yule speciation process prior.…”

Desert lizard diversity worldwide: effects of environment, time, and evolutionary rate

“…This diversity holds not only in comparison to other arid systems, but even in comparison to lowland tropical rainforests (Roll et al, 2017). At the local scale, more than 70 species of lizards (non-snakes) can occur in regional sympatry in arid Australia, a number that far exceeds those for the world's second-most species-rich lizard communities (e.g., Amazon rainforest, with 25-35 species; Duellman, 2005;Rabosky et al, 2019). Numerous hypotheses have been proposed to explain these dramatic differences in the number of species, including vegetative structure, habitat specificity and heterogeneity, termite abundance, and other ecological, biogeographic and historical factors (Pianka, 1972(Pianka, , 1989Morton & James, 1988).…”

Ensamble De La Herpetofauna en La Región Endémica De Belém, Estado De Pará, Este Del Amazonas, Brasil

“…The Amazon Forest harbors one of the greatest diversities of animals on Earth (Silva and Garda, 2011;Rabosky, von May, Grundler and Rabosky, 2019), including over 700 species of amphibians and reptiles, with high levels of endemism within these groups (Prudente, 2017;Hoogmoed, 2019;Ávila-Pires, 2020). This number is increasing mainly due to the discovery and description of new species for this biome (Oliveira et al, 2018;Ferrão, Moravec, Hanken and Lima et al, 2020;Mângia, Koroiva and Santana, 2020).…”