Cryptic speciation in Southern Ocean Aequiyoldia eightsii (Jay, 1839): Mio-Pliocene trans-Drake Passage separation and diversification

摘要: Abstract The species of the genus Aequiyoldia Soot-Ryen, 1951, previously known as Yoldia, are common, soft-substratum, sareptid bivalves. In Southern Ocean, eightsii (Jay, 1839) was originally described from Antarctic Peninsula and has also been reported in southern South America. A. woodwardi (Hanley, 1960) for Falkland/Malvinas Islands Tierra del Fuego, but this taxon recently synonymised within broadly distributed eightsii. received little attention across its distribution although taxonomy systematics remain uncertain, all have grouped under a single unit: Nevertheless, preliminary mtDNA comparisons demonstrated marked genetic divergence (>7%) between populations America Peninsula. order to further understand diversity biogeography Aequiyoldia, we analyzed different provinces Ocean including (SA), (FI), (AP), Kerguelen (KI). Individuals were characterized according typical diagnostic morphological measurements phylogenetic relationships reconstructed based on (cytochrome c oxidase subunit I). Patterns nucDNA intergenic transcribed spacers (ITS1, ITS2) estimated. statistical analysis external characteristics revealed two morphotypes: (1) individuals with morphology recorded nominal FI species, woodwardi, (2) SA, AP, KI, However, reconstructions suggest presence at least five lineages including: one lineage Island, Peninsula, America, last restricted Islands. Such results evidence that Polar Front represents an historical biogeographic barrier group after separation these lineages, they followed independent evolutionary pathways Ocean. Estimates time KI separated other close middle Miocene. Following this, AP SA occurred end Miocene around 7.5 Ma. Finally, diversified during Pliocene (∼4.5 Ma) (∼3.0 Ma). exhibited differences, 4% American individuals, suggesting woordwardi could be revalidated. Similarly, molecular rest support validity kerguelensis (Thiele, 1931).