| Abstract Detail
Recent Topics Posters Buggs, Richard J. A. [1], Pannell, John [2]. Species replacement due to hybridization and pre-adaptation. Plant polyploid complexes provide useful model systems for distinguishing between adaptive and nonadaptive causes of parapatric distributions in closely related lineages. Polyploidy often gives rise to morphological and physiological changes, which may be adaptive to different environments, but separate distributions may also be maintained by reproductive interference caused by postzygotic reproductive isolation. We tested both of these hypotheses in parapatric diploid and descendent polyploid races of the wind-pollinated herb Mercurialis annua, found in parapatry over an environmental gradient in northeast Spain. On the basis of a series of reciprocal transplant experiments in the field, and experiments under controlled conditions, we found that the diploid and polyploid populations are ecologically differentiated. However, they do not show local adaptation: the diploids have higher fitness than the polyploids across both diploid- and polyploid-occupied regions. We also showed that crosses between the diploid and polyploid produce sterile hybrid offspring, and that in artificial populations hybridization is highly asymmetrical in favor of the diploids. This is largely due to a difference in sexual system: the diploids are dioecious and the hexaploids monoecious. Using survey evidence we show that the diploids are currently displacing polyploids by advancing south on two separate fronts in Spain. Our results suggest that this is due to both to pollen swamping and ecophysiological superiority of the diploids.
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Related Links:
Richard Buggs webpage
John Pannell's homepage
1 - University of Oxford, Department of Plant Sciences, South Parks Road, Oxford, OX1 3RB, United Kingdom
2 - University of Oxford, Department of Plant Sciences, South Parks Road, Oxford, Oxfordshire, OX1 3RB, United Kingdom
Keywords:
polyploidy
hybrid zone
Mercurialis annua
reciprocal transplant
tension zone
range expansion
local adaptation.
Presentation Type: Recent Topics Poster
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P79051
Abstract ID:2731 |
