Evol Ecol Res 3: 311-330 (2001) Full PDF if your library subscribes.
Differentiation in reproductive strategy between sexual and asexual populations of Antennaria parlinii (Asteraceae)
Lisa M. O’Connell‡ and Christopher G. Eckert
Department of Biology, Queen’s University, Kingston, Ontario K7L 3N6, Canada
Author to whom all correspondence should be addressed:
e-mail: eckertc@biology.queensu.caABSTRACT
Plants exhibit wide variation in reproductive traits, and these traits often covary to form distinct strategies. Uniparental reproduction via self-fertilization is often associated with high reproductive effort and enhanced seed dispersal, the combination of which is viewed as an adaptive strategy in ephemeral or disturbed habitats. We investigated the hypothesis that uniparental reproduction via asexual apomixis is associated with a similar suite of traits and more frequent occurrence in disturbed habitats among populations of Antennaria parlinii, a dioecious species that exhibits wide variation in sexuality at the population level. By comparing 18 sexual and 21 asexual populations in Ohio, USA, we found that, as predicted, sexual populations were more likely to occur in wooded habitats than asexual populations, which were found more frequently in disturbed roadside ditches and fallow fields. As expected, plants in asexual populations produced, on average, twice as many seeds per inflorescence as plants in sexual populations. Asexual plants also exhibited much higher reproductive effort than sexual plants when compared in a common greenhouse environment, indicating a genetic basis for the difference in reproductive output observed in natural populations. Seeds of A. parlinii are equipped with plume-like pappus that enhances wind dispersal. Settling velocity in still air was lowest for diaspores with long, highly barbed pappus bristles and small seeds. Compared to sexual populations, asexual populations produced diapsores with longer, more highly barbed pappus and smaller seeds. Taken together, our results suggest that divergent selective pressures in different habitats have produced two distinct reproductive strategies in A. parlinii.
Keywords: anemochory, apomixis, asexuality, habitat disturbance, plant reproduction, pussytoes, reproductive effort, seed dispersal, sex.
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