PARENT SESSION
Oral Session #65: Evolutionary Ecology/ Population Genetics. Presiding: G. Gerrish.
Thursday, August 9, 2001. 8:00 AM to 12:00 PM. Hall of Ideas J.
Generating biodiversity: The phylogeography of a North American insect radiation.
McPeek, Mark1, Turgeon, Julie1, Thum, Ryan1, Stoks, Robby1, 1
ABSTRACT- Recent phylogenetic analyses have shown that two lineages of North American Enallagma damselflies (Odonata: Coenagrionidae) radiated very recently to give 18 extant species, and ecological studies have demonstrated that multiple habitat shifts occurred as part of this radiation. We are now using phylogenetic analyses using a 940 bp mtDNA fragment to reconstruct how speciation proceeded during this radiation. The phylogenetic relationships and geographic distributions of 54 haplotypes identify E. hageni as the ancestor of one radiating lineage. These data also show that E. hageni is comprised of disjunct Continental and Atlantic races that are indicative of restrictions to separate refuges during the last glacial period. Nine new species arose by at least three different speciation mechanisms from the Continental hageni race as it expanded its range following glacial retreat, but no new species arose from the Atlantic race. Three coastal plain endemics show very low genetic diversity and were each derived by a few populations differentiating from the Continental hageni in a local area. Three other widely distributed species show substantial polyphyletic origins within the Continental hageni. Parallel speciation events driven by habitat shifts appear to have created two of these species, and sharply contrasts with the apparent lack of ecological differentiation in the third. These results taken with previous studies suggest that both ecological and non-ecological speciation mechanisms can simultaneously drive radiation events.
KEY WORDS: biodiversity, radiation, speciation, phylogeography