ARONOWSKY, A.*; ANDERSON, L.C.; Louisiana State University; Louisiana State University: Corbulid bivalve phylogeny and the facilitation of ecosystem invasion

The bivalve family Corbulidae includes about 35 nominal genera of which 15 are extant. Although corbulids are often overlooked in malacologic and paleontologic collections, in part because of their diminutive size, the family is of particular interest biologically and paleontologically because it contains two extant invasive species (Potamocorbula amurensis and Varicorbula gibba), and at least 20 fossil species that came to dominate the freshwater systems they colonized. Thus corbulid history is marked by both ancient natural and modern anthropogenically-mediated invasions, making it an ideal clade in which to examine the traits thought to facilitate invasion. However, a clear understanding of corbulid evolutionary history is hindered by a number of taxonomic and systematic issues. We explore the phylogeny of the Corbulidae using separate and combined analyses of corbulid soft anatomy and shell morphology. This study, which builds upon previous research, uses shell characters that describe external ornament, hinge features, pallial line and sinus, and adductor muscle scars. The analysis includes four genera (Notocorbula, Potamocorbula, Anticorbula, and Lentidium) previously uncoded for shell morphology, as well as new outgroups: Mya and Lyonsia. Soft anatomical characters describe all aspects of corbulid anatomy, but focus on more variable features such as the siphons, mantle, gills, muscles, and digestive system. This study presents the first full anatomical descriptions for several corbulid species including P. amurensis. The corbulid phylogeny will be used to test hypotheses related to the number of times corbulids have successfully invaded ecosystems and which ecologic and life history characters correlate with these invasions.