Campbell, Lesley G. , Snow, Allison .
The life of a social radish: competition and its fitness consequences for advanced-generation, crop-wild hybrids.
Gene flow from crops to related species may lead to mixed populations of crop-wild hybrids and wild plants. The evolutionary impact of hybrids may depend on their ability to compete with neighboring wild relatives. We compared the effect of competition on the fitness of F3 and F8 hybrids (Raphanus raphanistrum x R. sativus) relative to their wild parent. First, we created 3 wild and 3 F1 hybrid radish populations in Pellston, Michigan, USA, and allowed them to evolve under semi-natural agricultural conditions for two generations. We also measured the fitness of back-crossed hybrid plants that had evolved under similar conditions for eight generations and compared them to a plants from another wild population. Pure and mixed pots of wild and F3 or F8 hybrids were established outdoors under four density treatments. Fitness components were measured as individual seed production, pollen and ovule fertility, flower production, and biomass. All measures of fitness were sensitive to density and neighbor identity. Mean F3 hybrid seed production was significantly lower than wild seed production at all densities, while F3 hybrid flower production and F3 hybrid biomass were significantly higher than those of wild plants under competitive conditions. F8 hybrid seed production was not significantly different from wild seed production at any density and these F8 hybrids had significantly higher flower production than the wild plants. F3 hybrid fitness may be limited by pollen and ovule fertility: ~50% of the F3 hybrids had reduced pollen fertility while less than 5% of the F8 hybrids had reduced pollen fertility, presumably due to a heterozygous reciprocal translocation. Over time, we expect that natural selection would favor plants with high pollen and ovule fertility. This study suggests that the fitness of advanced-generation hybrid radishes can exceed that of R. raphanistrum, but only under specific conditions.
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1 - The Ohio State University, Department of Evolution, Ecology and Organismal Biology, 318 W12th Ave, Columbus, Ohio, 43210, USA
2 - Ohio State University, Department of Ecology, Evolution, & Organismal Biology, 300 Aronoff Laboratory, 318 W. 12Th Avenue, Columbus, Ohio, 43210-1293, USA
Presentation Type: Poster
Location: Salon C, D & E - Gov Ballroom/Hilton
Date: Tuesday, August 16th, 2005
Time: 12:30 PM