Meeting Abstract

37.5  Tuesday, Jan. 5  The “Expansion-Contraction” Model of Pleistocene Biogeography: Rocky Shores Suffer a Sea Change? MARKO, P.B.*; HOFFMAN, J.M.; EMME, S.A.; MCGOVERN, T.M; KEEVER, C.; COX, L.N.; Clemson University; Clemson University; Clemson University; Limestone College; Simon Fraser University; Clemson University pmarko@clemson.edu

Among the many factors affecting the abundance and distribution of species, climate change has received the most attention. Historical data from eastern North America and western Europe provide an empirical basis for an “Expansion-Contraction” (EC) model of Pleistocene biogeography. Under the EC model, most northern hemisphere species survived in low-latitude glacial refugia, only re-populating higher latitudes through range expansions after the last glacial maximum (LGM). In addition to forming an important paradigm of modern biogeography, the EC model also provides a useful framework for understanding community-wide responses to climate change. To address the question of whether marine communities responded similarly to those on land, we conducted a survey of mitochondrial and nuclear DNA diversity from 14 rocky-shore northeastern Pacific species. Although mtDNA analyses from some species were consistent with large population expansions occurring near the LGM (the pattern expected if species recently recolonized the region), most species had histories consistent with long-term stability in population size, and thus regional persistence. Multilocus analyses for five species were consistent with mtDNA. Our results indicate that the LGM did not extirpate the majority of species in this community; instead, regional persistence during the LGM appears a common history. The demographic stability of only a subset of this community in the face of glacial-interglacial changes is consistent with the known ecological and physiological features of individual species and has important implications for understanding the impacts of climate change on patterns of rocky shore diversity.