Meeting Abstract
P2.3 Wednesday, Jan. 5 A phylogenetic perspective on the molluscan lineages in chemosynthetically-based ecosystems in the deep sea JUDGE, J.L.*; LINDBERG, D.R.; Univ. of CA, Berkeley; Univ. of CA, Berkeley jennajudge@berkeley.edu
The discovery of hydrothermal vents in 1977 changed the impression of the deep sea as a physically stable, dark environment with relatively low biodiversity and biomass. The vent environment is unique in that it is one of the only habitats in which the ecosystem is not based on energy fixed by photosynthesis, but by chemosynthesis performed by bacteria in a dynamic environment. Other marine habitats have been recognized as chemosynthetically-based including hydrocarbon seeps, sunken whale carcasses, and sunken wood. Organisms living in these communities are specialized for these conditions and may obtain their energy through symbiosis with the chemosynthetic bacteria. Each of the four extreme environments has been sampled at varying degrees, and although the communities’ method of energy distribution is similar, each comprises an assemblage of distinct and diverse taxa. Many of the scenarios addressing the antiquity and possible evolutionary paths of these faunas use taxonomic rather than phylogenetic units and assume directionality in habitat utilization. Using a current molluscan phylogeny, I examine the distribution of molluscan taxa occurring at chemosynthetically-based ecosystems. The resulting patterns suggest that the histories of lineages vary in both age and process by which they came to occupy the habitats that they exist in today. For instance, the most basal bivalve lineages occur at seeps, but not vents whereas both habitats share the same general assemblage of gastropod lineages. In addition, some lineages occur only on whale carcasses, and very few are shared between whale carcasses, vents and seeps. Only one clade (the mytilids) occurs at all four habitats. Further research is needed to test scenarios for the evolution of these lineages and their historical biogeography.
