Papers in the Biological Sciences


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Published in Evolution & Development (July-August 2007) v. 9, issue 4: 338-346. Copyright 2007, Blackwell. Used by permission.


The pea aphid, Acyrthosiphon pisum, exhibits several environmentally cued polyphenisms, in which discrete, alternative phenotypes are produced. At low-density, parthenogenetic females produce unwinged female progeny, but at high-density females produce progeny that develop with wings. These alternative phenotypes represent a solution to the competing demands of dispersal and reproduction. Males also develop as either winged or unwinged, but these alternatives are determined by a genetic polymorphism. Winged and unwinged males are morphologically less distinct from each other than winged and unwinged females, possibly because males experience fewer trade-offs between dispersal and reproduction. To assess whether shared physiological differences mirror the shared morphological differences that characterize the wing polyphenism and polymorphism, we used a cDNA microarray representing an estimated 10% of the coding genome (1,734 genes) to examine differential transcript accumulation between winged and unwinged females and males. We identified several transcripts that differentially accumulate between winged and unwinged morphs in both sexes, the majority of which are involved in energy production. Unexpectedly, the extent of differential transcript accumulation between winged and unwinged morphs was greater for adult males than for adult females. Together, these results suggest not only that similar physiological differences underlie the polyphenism and polymorphism, but that male morphs, like females, are subject to trade-offs between reproduction and dispersal that are reflected in levels of transcript accumulation and possibly genome-wide patterns of gene regulation. These data also provide a baseline for future studies of the molecular and physiological basis of life-history trade-offs.

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