title: Attack of the clones: reproductive interference between sexuals and asexuals in theCrepisagamic complex.
abstract: Negative reproductive interactions are likely to be strongest between close relatives and may be important in limiting local coexistence. In plants, interspecific pollen flow is common between co-occurring close relatives and may serve as the key mechanism of reproductive interference. Agamic complexes, systems in which some populations reproduce through asexual seeds (apomixis), while others reproduce sexually, provide an opportunity to examine effects of reproductive interference in limiting coexistence. Apomictic populations experience little or no reproductive interference, because apomictic ovules cannot receive pollen from nearby sexuals. Oppositely, apomicts produce some viable pollen and can exert reproductive interference on sexuals by siring hybrids. In theCrepisagamic complex, sexuals co-occur less often with other members of the complex, but apomicts appear to freely co-occur with one another. We identified a mixed population and conducted a crossing experiment between sexual diploidC. atribarbaand apomictic polyploidC. barbigerausing pollen from sexual diploids and apomictic polyploids. Seed set was high for all treatments, and as predicted, diploid-diploid crosses produced all diploid offspring. Diploid-polyploid crosses, however, produced mainly polyploidy offspring, suggesting that non-diploid hybrids can be formed when the two taxa meet. Furthermore, a small proportion of seeds produced in open-pollinated flowers was also polyploid, indicating that polyploid hybrids are produced under natural conditions. Our results provide evidence for asymmetric reproductive interference, with pollen from polyploid apomicts contributing to reduce the recruitment of sexual diploids in subsequent generations. Existing models suggest that these mixed sexual-asexual populations are likely to be transient, eventually leading to eradication of sexual individuals from the population.
authors: Department of Botany and Biodiversity Research Centre The University of British Columbia 6270 University Boulevard Vancouver British Columbia Canada V6T 1Z4.
authors: Evan
authors: E
authors: Hersh
authors: Department of Botany and Biodiversity Research Centre The University of British Columbia 6270 University Boulevard Vancouver British Columbia CanadaV6T 1Z4; Present address: Department of Biology McGill University 1205 Dr. Penfield Avenue Montreal Québec Canada H3A 1B1.
authors: Jaime
authors: J
authors: Grimm
authors: Department of Botany and Biodiversity Research Centre The University of British Columbia 6270 University Boulevard Vancouver British Columbia Canada V6T 1Z4.
authors: Jeannette
authors: J
authors: Whitton
keywords: Apomixis; eco‐evolutionary dynamics; interploidy crosses; interspecific pollen transfer; reproductive interference