Meeting Abstract

35.1  Monday, Jan. 5  Explaining patterns of diversity within ray-finned fish SANTINI, F*; CARNEVALE, G; HARMON, LJ; ALFARO, ME; Univ. of California, Los Angeles; Univ. of Pisa; Univ. of Idaho; Univ. of California, Los Angeles santini@eeb.ucla.edu

Using a large molecular timescale we present the first systematic study of the patters of diversity of ray-finned fish, and explore the potential paleobiological, biogeographical and ecological causes of such patterns. Our study indicates that the crown teleosts, which originated ~200 MY ago, experienced a significant shift in diversification rates compared to non-teleost actinopterygians. This shift coincides with, and might have been linked to, the occurrence of the fish specific genome duplication. Further shifts in diversification rates occurred subsequently in the ancestors of the two largest teleost clades: the ostariophysans, a group almost exclusively confined to freshwater that originated ~ 150 MY ago; and the percomorphs, a predominantly marine group that originated ~120 MY ago and subsequently diversified mostly in tropical ecosystems during the past 50 MY. Within these two clades we can further identify a number of species-rich and species-poor lineages. The existence of some of these species-poor lineages may be explained by the ecological niches they occupy (e.g., benthic deep sea environments), while in other cases (e.g., boarfish or john dories) it might be due to high extinction rates, as shown by the fossil record. Similarly, the high diversity of some other lineages might be linked to the appearance of new types of environments (e.g., coral reefs, where diverse clades such as gobies, blennies and wrasses radiated) or geographical areas where these lineages could diversify (e.g., the Amazonian basin, where a significant percentage of the diversity of ostariophysan fishes is located). We will also investigate the role that major extinction events, such as the KT, may have played in shaping the present diversity of teleost fishes.