Drummond, Christopher , Hamilton, Matthew .
Outcrossing rates and population structure in Lupinus microcarpus (Leguminosae).
Lupinus group Microcarpi forms a monophyletic and phenotypically diverse group of annual species and varieties that are widely distributed in western North America. Pollinator mediated selection has been proposed to act on floral display in Lupinus (e.g., banner spot color change in post-reproductive flowers), leading to increased pollinator efficiency and higher levels of male fitness via outcrossing. Progeny arrays were collected from multiple varieties and populations of L. microcarpus with differences in color change phenotype, to estimate variation in mating system parameters. Seven novel nuclear microsatellite loci were developed to estimate population structure and outcrossing rates, and simulation studies were conducted to determine the most powerful genotyping design (number of families and progeny per family) for estimating population outcrossing rates under a multilocus, mixed mating model with fixed sampling effort. Values for inbreeding (F), outcrossing (t), correlation of outcrossing (rt), correlation of paternity (rp) and number of alleles per locus (k) were estimated from preliminary data and used to generate a set of simulated populations. To determine the sampling design with the lowest expected variance and/or bias in outcrossing estimates, the simulated populations were randomly resampled using different combinations of family x progeny. Using the most powerful sampling design, initial estimates from natural populations of L. microcarpus indicate low to moderate outcrossing (t ~ 0.0 - 0.5) and potentially high rates of pollen discounting. These findings are consistent with estimates of population structure in L. microcarpus, with high levels of subdivision (FST ~ 0.3) and substantial deficiency of heterozygotes within populations (FIS ~ 0.7). Furthermore, sympatric varieties (e.g., L. microcarpus var. horizontalis and var. densiflorus) are genetically differentiated, with low but detectable levels of hybridization.
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1 - Georgetown University, Department of Biology, 406 Reiss Sciences Bldg, 37th & O St NW, Washington, DC, 20057
Presentation Type: Oral Paper
Date: Monday, August 15th, 2005
Time: 9:15 AM