Measurement of gene flow through pollen and seed in continuous and discontinuous populations
John D. Nason
Dept. of Biological Sciences
University of Iowa
Iowa City, IA 52242-1324
email:  John-Nason@uiowa.edu

Due to differences in their physical properties and in the vectors that disperse them, pollen and seed movement may generate spatial patterns of gene dispersion that differ in both continuous and discontinuous populations. Studies of pollen flow have employed statistical genetic approaches that fall into one of two categories; those that estimate rates of pollen flow into discrete populations but do not provide estimates of male fertility and pollen movement within populations and, conversely, those that infer male fertilities but do not adjust these estimates for cryptic pollen flow originating outside of the study population. Combining statistical approaches, I will present a model that simultaneously estimates rates of total gene flow and male fertilities adjusted for cryptic pollen gene flow from genotypic data. In contrast to the problems of quantifying pollen dispersal, the development and application of statistical models to estimate gene flow via seed has been hampered by the limited availability of suitable maternally inherited chloroplast and mitochondrial markers. As a solution to this problem, I will present a general framework for estimating pollen and seed components of gene flow from the observed distribution of genotypes at biparentally inherited loci. The model much more rapidly generates direct estimates the levels of pollen flow received by individual maternal plants and populations than does currently available methods. Moreover, once a population level estimate of pollen flow has been obtained, nuclear markers, such as allozymes, can be used to obtain direct estimates of seed immigration from the multilocus genotypes of dispersed seeds and seedlings. The application of these models to investigating pollen, seed, and gene movement in continuous and spatially isolated populations will be discussed.