Ecological impacts and evolutionary consequences of the European green crab invasion

Edwin Grosholz, Ph.D.
University of California, Davis

Wednesday, October 13, 1999
3:00 p.m.—Pacific Forum

grosholz2.jpg (4434 bytes)Invasive species rank among the most serious threats to the health of coastal ecosystems. We have used long-term data and experiments in both field and laboratory to quantify the ecological consequences of the invasive European green crab on more than 20 species of invertebrates and 13 species of shorebirds in Bodega Harbor, CA. Within three years of the invasion, our results show that green crab predation has resulted in a 90-95% reduction of several native invertebrates, including clams and shore crabs. These prey populations have remained at very low abundances for five years since the introduction of the green crab. Also, significant indirect effects of green crab predation have also occurred during the same period, including large increases in non-prey species such as polychaetes and tube-building crustaceans. However, changes in invertebrate prey populations have not yet resulted in changes in shorebird populations wintering in the Bodega Harbor system. We have also begun to quantify the evolutionary consequences of the green crab invasion by comparison of North American with a parallel invasion in Australia. We show that crabs in invading populations are significantly larger in comparison with the native European range. Recent molecular genetic comparisons of native and introduced populations show substantial reduction in genetic diversity suggesting the possibility that the apparent "ecological release" may have genetic basis. We are now developing methods to test this idea.

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Last updated: December 19, 2000