Phylogeographic structure and demographic history of the limpet Siphonaria lessoni in the southern coasts of South America

NUÑEZ JD; FERNANDEZ IRIARTE P; EH OCAMPO; IUDICA C; CLEDÓN M

Mar del Plata

Congreso; Costal and estuarine research federation; 2012

The historical processes that could have mainly influenced the genetic structure of species are associated to environmental changes of Pleistocene glacial cycles. These climatic changes (temperature, marine currents and loss of coastal habitats) may have affected the abundance and geographic distribution of marine species of temperate coastal habitats. In the present work, 552 pb of the COI of 92 individuals were sequenced to analyze the genetic structure of limpets Siphonaria lessoni. The individuals were collected at the intertidal coast of the Southern Atlantic (Mar del Plata, San Antonio, Puerto Madryn and Ushuaia) and Pacific (Valdivia and Valparaíso). Using S. lateralis as the outgroup, the haplotypes of S. lessoni were assigned to the Pacific (n=33) and Atlantic (n=59) basins. The AMOVA between clades explained the highest proportion of genetic divergence (FST=0.78, P< 0.05). The Pacific clade (Nh=28, S=33, h=0.989, pi=0.008) yielded more haplotypes (Nh) and polymorphic sites (S) as well as higher haplotypic (h) and nucleotide diversity (pi) than the Atlantic clade (Nh=16, S=19, h=0.540, pi=0.002) did. Both Tajima’s D and Fu’s Fs were significant and negative, thereby suggesting that both clades are in population expansion. In concordance, the haplotype network for each clade showed a star-like phylogeographic pattern. The Bayesian Skyline analysis, using 1% of substitution rate, revealed an older coalescence in the Pacific clade (0.295 my) than in the Atlantic clade (0.04 my). This work reports the first evidence of Pacific-Atlantic geographic isolation for a coastal species, which is probably related to changes in sea level and temperature due to the extended glaciation periods that occurred in the region throughout the Pleistocene.