Molluscs (snails, octopuses, clams and their relatives) have a great disparity of body plans and, among the animals, only arthropods surpass them in species number. This diversity has made Mollusca one of the best-studied groups of animals, yet their evolutionary relationships remain poorly resolved. Open questions have important implications for the origin of Mollusca and for morphological evolution within the group and attempts to understand the early evolution of molluscs become even more complex when considering the large diversity of Cambrian fossils.
To better resolve the relationships among molluscs, a group led by researchers at Brown University used RNA-Seq to generate transcriptome data for 15 species that, in combination with existing data, represent for the first time all major molluscan groups. This well-resolved tree will constitute a framework for further studies of mollusc evolution, development and anatomy.
The study is noteworthy also because it is the first to place Monoplacophora, the mysterious group of deep-ocean animals that superficially resemble limpets. Scientists had thought the group was extinct until a specimen was caught in 1952 off the coast of Mexico. Turns out, the monoplacophorans are a sister clade to cephalopods, which encompasses octopuses, squid, and nautiluses. Who would have guessed?
Read more about this at: The Brown Daily Herald – Mollusc family tree pruned by Michael Weinstein
- Smith SA, Wilson NG, Goetz FE, Feehery C, Andrade SC, Rouse GW, Giribet G, Dunn CW. (2011) Resolving the evolutionary relationships of molluscs with phylogenomic tools. Nature [Epub ahead of print]. [abstract]