HART, M.W.*; SUNDAY, J.; KEEVER, C.C.; Simon Fraser Univ.; Simon Fraser Univ.; Simon Fraser Univ.: Dispersal and climate history in sea star population genetic structure
The NE Pacific bat star Patiria miniata is widespread and abundant in southern and central California, the outer coasts of British Columbia, and southeast Alaska, but is rare or absent north of Cape Mendocino (CA) to Cape Flattery (WA). This range disjunction includes the maximum southern extent of the last Pleistocene glaciers (LGM). One plausible explanation for this present-day distribution is post-Pleistocene expansion (via planktotrophic larval dispersal) from southern and northern glacial refuges without gene flow between their descendants. An alternative explanation is northern extirpation followed by post-Pleistocene range expansion from California northward, plus some ecological process that excludes this species from shallow marine habitats of Oregon and Washington. Our recent genetic studies appear to refute both of these simple explanations. For example, mtDNA measures of population differentiation between Bodega Bay, CA (south of the LGM) and Tofino, BC (on Vancouver Island, well north of the LGM) are very small (&PhiST=-0.007, P=0.52). In contrast, differentiation between BC populations on Haida Gwaii (Queen Charlotte Islands) and Vancouver Island (<500 km apart) is very large (&PhiST=0.226, P<<0.01). The former pattern is probably due to post-Pleistocene gene flow from south to north that re-established some northern populations extirpated by ice. The latter pattern is probably due to lengthy isolation of some populations in northern ice-free refuges. The absence of more recent gene flow on this smaller scale might be due to divergence of the (northward) Alaska and (southward) California current systems offshore of Queen Charlotte Sound. Notably, the south-to-north gene flow that connects California and Vancouver Island populations is in the direction opposite to the California current that appears to isolate northern populations from each other.
