Molluscan Evolution in the Pannonian Lake (Late Miocene, Hungary)

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9706230 Geary The late Miocene Pannonian lake harbored one of the most diverse endemic lacustrine mollusc faunas ever known, including approximately one thousand described species, dozens of endemic genera, several endemic subfamilies, and two endemic families. In spite of the textbook nature of this case (e.g. Stanley 1979- Ager 1963, 1993, Sepkoski 1993), the evolution of the Pannonian lake malacofauna is known only from a few studies of individual lineages (e.g. Geary 1990a- Muller and Magyar 1992a), but has not been approached in a comprehensive way. In addition to its impressive malacofauna, the Pannonian lake presents an ideal system for paleontological research because its paleoenvironment and stratigraphy are extremely well studied. Many aspects of lake paleoenvironment and history, including the origin of the lake, its sedimentation and water depth, lake level fluctuations, paleogeography, and paleoclimate have been the focus of recent work. A newly revised chronostratigraphy has just been completed, which incorporates detailed biostratigraphic, seismic stratigraphic, and magnetostratigraphic data. The PI's Hungarian collaborators, Drs. Imre Magyar and Pal Muller, have been important contributors to this body of knowledge. The work we propose here includes several smaller projects that will further enhance our paleoenvironmental understanding. Thus, all the pieces are in place for a detailed examination of the relationship between environmental and evolutionary change in this classic system, We propose to examine the evolutionary radiation of the major clades of Pannonian lake molluscs in this detailed paleoenvironmental context. We intend to: 1) conduct a comprehensive review and taxonomic revision of four of the most diverse molluscan families, 2) use morphometrics to characterize geographic variation and morphological change over time in selected lineages from the Pannonian lake, and 3) interpret the taxonomic and morphological results in an environmental context. Specifically, we will test the idea of coordinated, stasis among various molluscan lineages, and we will examine how environmental stability or change influenced the diversity and morphological evolution of Pannonian lake molluscs. Geologically gradual tempos appear to have been documented in several Pannonian basin mollusc lineages (Geary 1990a; Muller and Magyar 1992a; Staley 1992- Staley et al. 1992). A more comprehensive view of Pannonian lake molluscan evolution, including detailed documentation of change in additional lineages, will contribute to our understanding of the mechanisms behind various evolutionary tempos.