High levels of population genetic differentiation in the American crocodile (Crocodylus acutus)

Abstract

The American crocodile ( Crocodylus acutus ) is a widely distributed species across coastal and brackish areas of the Neotropical region of the Americas and the Greater Antilles. Available information on patterns of genetic differentiation in C. acutus shows a complex structuring influenced by interspecific interactions (mainly hybridization) and anthropogenic actions (mostly historical hunting, recent poaching and unintentional translocation of individuals). Moreover, recent work suggests C. acutus as a complex of cryptic species with preliminary proposals for taxonomic reassignment. Until recently, most population genetics research has primarily focused on present hybrid zones with other new world crocodilians . In this study, we used data on mitochondrial DNA control region and 11 nuclear polymorphic microsatellite loci to assess the degree of population structure of C. acutus in South America, North America, Central America and the Greater Antilles. We used traditional genetic differentiation indices, Bayesian clustering and multivariate methods to create a more comprehensive picture of the genetic relationships within the species across its range. Analyses of mtDNA and microsatellite loci show evidence of strong population genetic structure in the American crocodile, with unique populations in each sampling locality. Our results support previous findings showing large degrees of genetic differentiation between the continental and the Greater Antillean C. acutus. We report three new haplotypes unique to Venezuela, which are considerably less distant from the Central and North American haplotypes than to the Greater Antillean ones. Our findings reveal genetic population differentiation between Cuban and Jamaican C. acutus and offer the first evidence of strong genetic differentiation among the populations of Greater Antillean C. acutus. The information generated here is crucial for local and regional planning and conservation of the species, and contributes to the ongoing discussion on potential taxonomic revision for C. acutus .

Pleistocene sea level changes and crocodile population histories on the Isthmus of Panama: A comment on Avila‐Cervantes et al. (2020)

“…2004; Piperno 2007) and almost certainly played important roles in past distributions given what we know about the modes of life and life histories of C. acutus (Mazzotti 1999; Rossi et al. 2020). Incorporating paleoclimate data into demographic models should therefore be enriching.…”

“…We present these hypotheses not as definitive explanations but as equally valid potential drivers that must be considered in conjunction with sea level. Climate and precipitation on the Isthmus changed dramatically over the late Pleistocene and Holocene (Lachniet et al 2004;Piperno 2007) and almost certainly played important roles in past distributions given what we know about the modes of life and life histories of C. acutus (Mazzotti 1999;Rossi et al 2020). Incorporating paleoclimate data into demographic models should therefore be enriching.…”