PARENT SESSION
Symposium 20: Evolution on ecological time scales
Organized by: A Hendry, D Réale, and G Fussmann
Thursday, August 11, 1:30 PM - 5:00 PM, Meeting Room 517 B, Level 5, Palais des congrès de Montréal

Geographical variation in ecological specialization: Pea aphids 125 years after introduction to North America.

Via, Sara^*,1, ¹ University of Maryland, College Park, MD, USA

ABSTRACT- Populations of pea aphids on alfalfa and red clover are known to be highly ecologically specialized in host plant use-- on average, they perform very poorly on the alternate host in reciprocal transplants. This specialization appears to be a step toward speciation, given that habitat choice leads to partial reproductive isolation in specialized populations. Ecological host specialization has been seen in pea aphids not only in the eastern and midwest sections of the US, but also in France and Sweden, suggesting that the pea aphids introduced to North America from Europe in the mid-1800s were specialists. However, recent experiments reveal that pea aphids from red clover in Washington state and Vancouver, BC can use both hosts nearly equally, even though pea aphids from alfalfa in the same regions are as specialized as those collected in New York or Iowa. The possible causes of this geographical variation in specialization, and its consequences on the potential speciation of this pair of host races will be discussed in the context of evolution within invasive and introduced taxa.

Key words: insect ecology, speciation, invasive species, host races