Bivalves in Time and Space:
Testing the accuracy of methods to reconstruct ancestral morphology, dates, geography, and diversification patterns
This project seeks to develop bivalves as a preeminent model for macroevolutionary studies. We will construct evolutionary family trees (phylogenies) for two commercially important bivalves — the cockles/giant clams (family Cardiidae) and the poorly defined “pitarine” group of hard-shelled clams (family Veneridae) — using a combination of morphology and DNA sequence data from multiple genes. Each of these two phylogenies will include approximately 200 living and 100-200 extinct species. Using simulations and the exceptional bivalve fossil record, the project will test how well standard methods work that use data only from living species to estimate the ages, physical traits, and geographic distributions of ancestors throughout history. We will also use the phylogenetic results to determine in detail how bivalves have diversified over space and time, including why they are much more diverse in the tropics than in temperate regions.
Nearly every aspect of modern comparative biology rests on the assumption that, given a phylogeny of living species, we can estimate the attributes of their ancestors. But reconstructions based on living species have broad uncertainties because the methods have not been tested against a precise history due to the incomplete fossil record of nearly all organisms that have been studied. One of the few groups in which we can test estimates against their recorded history are the bivalves, which are abundant today, rich in diversity, and have an excellent fossil record. By testing all the major methods of reconstructing ancestral traits, ages, and distributions — in addition to bivalve phylogenetics — the results should have far-reaching importance to fields as diverse as genomics, immunology, and ecology.
Participants at the Third Annual BiTS Meeting in Chicago, October 17-18, 2011 (left to right): Jan Johan ter Poorten, Rüdiger Bieler, Nathanael Herrera, Nick Matzke, David Jablonski, Scott Steppan, Paula Mikkelsen, and André Sartori.