Abstract

ALONSO, M.P  and  FERNANDEZ IRIARTE, P.J. Genetic structure and demographic history of striped weakfish Cynoscion guatucupa (sciaenidae) from the southwestern atlantic. BAG, J. basic appl. genet. [online]. 2015, vol.26, n.2, pp.7-15. ISSN 1852-6233.

In South America, the Pleistocene was characterized by important environmental changes related to glacial cycles, which had significant effects on the evolutionary history of several marine species. To evaluate the pattern of demographic history and the genetic structure of striped weakfish Cynoscion guatucupa, a 401 bp fragment of the mitochondrial Cytochrome b gene was sequenced from 92 individuals from three coastal areas in Argentina and one in Brazil in the southwestern Atlantic. Haplotype diversity was high, whereas nucleotide diversity was low among all sampling sites. The star-like pattern was not phylogeographically structured, in agreement with the AMOVA analysis. The Fu’s test was negative and highly significant whereas the mismatch analysis yielded an unimodal distribution indicating population expansion. The mutation rate of Cytochrome b, calibrated with pairs of species of Cynoscion found on both sides of the Isthmus of Panama was estimated at 0.006 substitutions per million years. The Bayesian skyline plot was used to date changes in population size through time and revealed a coalescence time of 155,000 years. Cynoscion guatucupa exhibited a mutation accumulation pattern associated with a rapid population growth after a period of low effective population size, probably linked to climatic changes in the late Pleistocene.

Keywords : Genetic structure; Cytochrome b; Marine fish; Pleistocene; Mutation rate.