Meeting Abstract
P1.38 Friday, Jan. 4 Phylogeny, biogeography and systematics of hydrothermal vent and methane seep Amphisamytha (Ampharetidae, Annelida) STILLER, J.*; ROUSSET, V.; PLEIJEL, F.; CHEVALDONNé, P.; VRIJENHOEK, R.; ROUSE, G.; SIO, UCSD; SIO, UCSD; Univ. of Gothenburg; Station Marine d’Endoume Marseille; MBARI; SIO, UCSD jstiller@ucsd.edu
Amphisamytha has five currently recognized species. Of these, A. galapagensis has been reported from various hydrothermal vents and hydrocarbon seeps across the Pacific Ocean. Here, Amphisamytha from a range of Pacific habitats, as well as Amathys lutzi from Atlantic vents, have been studied using morphology and DNA sequences. The phylogenetic analyses revealed a clade associated with chemosynthetic habitats comprising most of the known species, and three lineages that are regarded as new species. One new species is from vents of the northeast Pacific, another spans much of the East Pacific Rise, and is sympatric with A. galapagensis for part of its range. The third is in sympatry with A. vanuatuensis at western Pacific hydrothermal vents. The morphologically distinct A. lutzi was nested within Amphisamytha and is regarded as a junior synonym. The range of the ‘cosmopolitan’ A. galapagensis is restricted to the southern East Pacific Rise and the Galápagos Rift. A. fauchaldi, previously only known from the Gulf of California, is recorded from cold seeps off Costa Rica and Oregon. To assess the evolutionary ages of the lineages, previously published nucleotide substitution rates were employed. According to a molecular clock calibrated for shallow-water invertebrates, the Atlantic-Pacific species pair split less than three million years ago – a time where the Panamanian sill was already too high for deep-water dispersal – implying that this clock is ‘too fast’ for Amphisamytha. A slower clock specific for deep-sea annelids dates the most recent common ancestor for the deep-water clade at 40 million years, and the separation of the Pacific and Atlantic species to about 15 million years.
