Meeting Abstract

S3.8  Tuesday, Jan. 4  Range expansion and speciation in the dynamics of the marine latitudinal diversity gradient JABLONSKI, D.*; BERKE, S.K.; KRUG, A.Z.; TOMASOVYCH, A.; ROY, K.; VALENTINE, J.W.; Univ. of Chicago; Univ. of Chicago; Univ. of Chicago; Univ. of Chicago; Univ of California, San Diego; Univ of California, Berkeley djablons@uchicago.edu

The most dramatic shallow-water biodiversity pattern, the latitudinal diversity gradient, is shaped by the tendency for clades (operationally here, genera) to originate in the tropics, then expand to higher latitudes while retaining their tropical presence. The key process of range expansion is apparently linked to speciation. Genera spanning the tropics-to-poles gradient tend to contain more species within each 5-degree latitudinal bin or climate zone than do genera restricted to that bin or climate zone, suggesting that factors promoting regional diversification also promote clade range expansion. Older and more widespread genera are consistently more species-rich and encompass broader overall temperature ranges than do young genera. Surprisingly, however, individual species within widespread genera do not encompass broader temperature ranges than species from young or narrow-ranging genera. Thus, genera do not expand their latitudinal ranges via range-expansion of species that have enlarged their temperature tolerances. Instead, genera appear to speciate up the latitudinal gradient, via species that shift their preferred mean temperatures, a process evidently most accessible to clades having higher diversification rates within latitudinal bins and climate zones as well. These hypotheses can be tested in greater detail using species-level molecular phylogenies, now in progress.