Population genetic structure of the Antarctic ascidian Aplidium falklandicum from Scotia Arc and South Shetland Islands

MILAGROS DEMARCHI; MARINA CHIAPPERO; MARCOS TATIÁN; RICARDO SAHADE

POLAR BIOLOGY

SPRINGER

Año: 2010 p. 1567 - 1576

0722-4060

In sessile marine organisms, gene Xow betweenpopulations depends mainly on free-living reproductivestages (such as larvae and gametes), and usually thestrength of genetic structure is related to the time spent inthe plankton and physical factors as oceanographic condi-tions. In Antarctica, abyssal depths that surround the conti-nent and the Polar Front are considered strong barriers forbenthic marine fauna, keeping the continent isolated fromother shelves. The only available shallow water habitatsbetween South America and the Antarctic continent arethose around the Scotia Arc Islands; there are no shallowwater habitats between the other southern continents andAntarctica. In this work, ISSRs-PCR markers were usedto study the genetic structure of populations of Aplidium alklandicum, a compound ascidian with short-lived lecito-trophic larvae. A highly signiWcant genetic diVerentiation(ST =0.405; P <0.05) and a pattern of isolation by dis-tance were found. A genetic landscape approach identiWeda discontinuity in genetic diversity, coincident with thesouthernmost registered position of the Polar Front. ForA.falklandicum, a species with presumably low capacity oflong distance dispersal, the abyssal depths together with thelarge geographic distances create a barrier for gene flow.