Distribution and genetic differentiation of Macrobrachium jelskii (Miers, 1877) (Natantia: Palaemonidae) in Brazil reveal evidence of non-natural introduction and cryptic allopatric speciation

Abstract

Macrobrachium jelskii (Miers, 1877) occurs in all major Brazilian drainage basins. Considering its wide distribution and the supposed isolation of certain populations, we evaluated phylogenetic relationships among populations from several river basins. Analyses of molecular data using the mitochondrial COI and 16S genes suggest the division of the species into two clades, "Amazonian" and "coastal." The genetic divergence between these two groups is greater than the genetic divergence within the respective groups. Based on the time of divergence and the probable natural distribution of the species, we suggest two evolutionary scenarios to explain the origin of the coastal clade. The first scenario considers the capacity of M. jelskii to tolerate saline environments. The second is based on Pliocene climate changes that would have caused river confluence from sea level regression. The two clades occur sympatrically but this is a recent condition. The wide geographic distribution and low genetic divergence of the Amazonian clade allows us to propose that the current distribution of M. jelskii is partly due to human activity. Pending future analysis, the absence of a consistent morphological synapomorphy precludes the description of a new cryptic taxonomic entity for M. jelskii.