HYPERDIVERSITY IN MOLLUSCS AND PALAEOBIOTIC ANALYSES: WHAT ARE ‘SPECIES’ AND ARE THEY USEFUL?

Over the past few decades biodiversity expeditions have demonstrated living marine tropical molluscs to be much more taxonomically diverse than ever previously suspected. Predominantly this new diversity is located at the tree tips, often as so-called ‘semi-cryptic’ species and these are scattered widely across the molluscan tree. A similar relationship of taxonomic and morphological diversity very likely applied during the Neogene and maybe the entire Cenozoic. Integrative studies of the hyperdiverse neotropical snail Polystira (Oligocene-Recent) show that it may be possible to delimit extinct species conceptually equivalent to living DNA-delimited ones. Continuing work suggests Polystira to comprise 120 living species (85% newly delimited) and >180 extinct species (99% newly delimited) within the faunas studied to date. Though Polystira has remarkable ‘hidden‘ diversity, it may not be truly exceptional. If this is so, then it may be that most traditional fossil ‘species’, at least those within species-rich clades, represent supraspecific groupings. I will discuss whether ‘true-species’ level precision is obtainable or necessary for tropical palaeodiversity and biogeographic studies, and if not, what might take its place. How could we discover and share these natural and analysable units? One way would be to build a community-wide on-line database using a tool such as Scratchpads to tie taxonomic expertise, morphological data and ontologies, with molecular trees, literature, museum types and other vouchers. A programme built along these lines would help train a generation of students to develop a truly integrative systematics based on character and taxon discovery rather than merely name usage. Use of such tools as data aggregators would enable us to build a Cenozoic pantropical molluscan dataset for uncovering detailed systematic, palaeobiogeographic and macroecological patterns at up to global scale.