Deep phylogeographic divergence among populations of limpet Siphonaria lessoni on the east and west coasts of South America

JD NUÑEZ; JP FERNÁNDEZ IRIARTE; EH OCAMPO; C IUDICA; M CLEDÓN

MARINE BIOLOGY

SPRINGER

Lugar: Berlin; Año: 2015 vol. 162 p. 595 - 605

0025-3162

The historical processes that have influencedthe genetic structure of many species are often associatedwith environmental changes of the Pleistocene glacialcycles. These climate changes involve temperature oscil-lation, marine currents and loss of coastal habitats, whichcould have affected the abundance and geographic distri-bution of marine species in temperate coastal habitats. Inthis work, a 552-bp mtDNA fragment of COI locus of 92individuals was sequenced to analyze the genetic structureof the limpet Siphonaria lessoni. Individuals were col-lected on the intertidal coast of the Southern Atlantic (Mardel Plata, San Antonio Oeste, Puerto Madryn and Ushuaiain Argentina) and the Southern Pacific (Valdivia and Val-paraíso in Chile). S. lessoni displayed two distinct line-ages that were nearly reciprocally monophyletic betweenthe Atlantic and Pacific coasts. AMOVA tests revealed theexistence of strong population genetic structure. The Pacificcoasts yielded more haplotypes and polymorphic sites aswell as higher haplotype and nucleotide diversity than theAtlantic clade did. Both Tajima?s D and Fu?s F s were sig-nificant and negative, suggesting that limpet populationsare in population expansion or have recently expanded.Accordingly, the haplotype network for each clade showeda star-like phylogeographic pattern. From IMa analysis,the divergence time between Pacific and Atlantic popula-tions was 100,000?1,000,000 ybp with gene flow occurringfrom Pacific to Atlantic populations. The Bayesian Skylineanalysis revealed an older coalescence in the Pacific clade(30,000?300,000 ybp) as compared to that in the Atlan-tic clade (4,000?40,000 ybp). This work reports evidenceof Pacific?Atlantic geographic isolation with asymmetricmigration, which is probably related to changes in sea leveland temperature due to the extended glaciation periods thatoccurred in the region throughout the Pleistocene.