Meeting Abstract
Marine deposits of sunken wood provide occur at moderate depths (generally less than 2000 m) and provide the fundament for chemoautotrophic deep-sea communities with an extensive wood-endemic invertebrate fauna. Wood-dwelling lineages have been proposed as a “transitional” fauna that gave rise to invertebrates in vent and seep systems; a deep time phylogenetic framework could thus help explain the colonization of many deep sea “extreme” environments. For example a major clade of polyplacophoran molluscs (chitons) incorporating the majority of deep sea species, Lepidopleurida, originated in the early Carboniferous (ca. 350 Mya). New fossil evidence indicates a major bottleneck in Polyplacophora at the late Devonian mass extinction event (ca 375–360 Mya) followed by the emergence and diversification of the modern fauna in the Carboniferous. Yet the chiton fauna on sunken wood does not comprise a clade or radiation; wood-endemic species encompass multiple colonization events with several independent evolutionary origins of co-occuring wood species. These separate lineages correspond to differences in micohabitat and feeding strategies—a point that is remarkable only in light of the overall conservatism of chitons, which are often called ‘living fossils’. Early fossil forms include fossils with strong similarities to modern wood-endemic taxa. Evidence from chitons and other marine invertebrates indicates that the availability of abundant woody debris entering marine systems in the early Carboniferous may have played a key role in biodiversity recovery after the late Devonian mass extinction. This phylogenetic context changes the interpretation of interactions among wood and other ever more geothermally extreme deep sea oases.
