Hardiman, Nicole , Culley, Theresa M. .
The role of hybridization in reproduction and establishment of invasive Pyrus calleryana (Callery pear).
Pyrus calleryana is an emerging invasive tree now found across much of the United States. Originally introduced as an ornamental, the species has rapidly spread in the last decade across disturbed or open natural areas. Invasive populations have previously been found to be the progeny of genetically distinct cultivars of the Callery pear, with high genetic admixture in invasive individuals. This intraspecific hybridization serves to increase genetic diversity and/or create novel genetic combinations within invasive individuals, potentially resulting in hybrid vigor. Hybrid vigor can be manifested in either F1 or later generation hybrids, and possibly within only a subset of different hybrid combinations. This study examines variation in maternal reproduction and progeny establishment ability differing hybrid types. The first goal was to examine maternal reproduction among cultivars and establishment ability in resulting early generation hybrids (F1). The second goal was to compare early versus later generation hybrids (F2, BC1, etc.) of unknown parentage. Measured traits consisted of both maternal reproductive investment (fruit mass, seed mass and seed number) and establishment ability of progeny (percent germination, percent mortality, photosynthetic rate, and biomass). In both data sets, significant differences were found for maternal reproductive measures and overall biomass, but none of the other measures were significant. Cultivated individuals set more and larger seeds than invasive individuals, which is probably the result of an abundance of available resources in cultivated settings. Additionally, F1 progeny appear to have an establishment advantage by accumulating greater biomass versus later generation hybrids, which provides evidence for early-acting hybrid vigor followed by a breakdown of hybrid advantage in subsequent generations.
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1 - University of Cincinnati, Department of Biological Sciences, 614 Rieveschl Hall, Cincinnati, Ohio, 45221, USA
Presentation Type: Poster:Posters for Sections
Location: Ball Room & Party Room/SUB
Date: Monday, July 28th, 2008
Time: 12:30 PM