Phylogeography of weakfish Cynoscion guatucupa (Perciformes: Sciaenidae) from the southwestern Atlantic

Abstract

The genetic structure of populations/species was established during the Quaternary glaciations. Over the last 250 ka (Pleistocene), the South American marine biogeographic history recorded three main glaciations: the most extensive one between 140 and 180 ka, a minor one between 60 and 70 ka, and the last glaciation approximately between 15 and 35 ka. With the aim of assessing the pattern of molecular diversity and historical demography of weakfish (Cynoscion guatucupa), a 365 bp sequence of the mitochondrial control region was amplified at four coastal sites located in the southwestern Atlantic. Haplotype diversity was high, whereas nucleotide diversity was low and similar at each sample site. AMOVA failed to detect population structure. This lack of differentiation was subsequently observed in the distribution of samples sites in the haplotype network. Fu’s Fs was negative and highly significant while the mismatch analysis yielded a unimodal distribution, indicating a global population expansion. The Bayesian skyline plot revealed a coalescence time of weakfish population at approximately 210 ka, and a very rapid expansion from 180-190 ka, probably caused by a habitat expansion, as these two events coincide in time.

Keywords

• bayesian skyline plots
• glacial cycles
• mitochondrial dna
• control region
• population genetics
• marine fish
• atlantic coast
• pleistocene