Dissertation Research: Gene Flow, Reproductive Success and Inbreeding Depression in Fragmented Populations of Three Tropical Understory Trees

University Of Wisconsin-Madison, Madison WI

Investigators

Abstract

As tropical forests are cleared for agriculture, tropical trees become restricted to isolated "islands" of habitat. If pollen and seeds do not move effectively among these fragments, local mating occurs, increasing inbreeding and the erosion of genetic diversity. Inbreeding and reduced genetic diversity, in turn, can diminish seed production and seedling vigor, threatening population viability. This study uses genetic markers to study how fragmentation affects pollen movement and inbreeding in three animal-pollinated tropical tree species in Costa Rica. DNA fingerprinting will be used to determine pollen sources for seeds produced in forest fragments and how levels of inbreeding and genetic diversity are affected by pollen movement. Comparing patterns of gene flow and seedling vigor between fragments and a nearby continuous forest will allow assessments of genetic threats posed by fragmentation. Geographic analyses will show how patterns of gene flow are affected by fragment size and surrounding landscapes. Declines in biological diversity represent a profound global threat. This study will illuminate how habitat loss and fragmentation are affecting reproductive success, genetic diversity and inbreeding, all of which can reduce population viability. Because they depend so obviously on animals for pollination and seed dispersal, tropical trees in forest patches are at particular risk of extinction. As plants represent the foundation for biological productivity and diversity, such losses can result in cascades of extinctions. The data from this study are thus needed to identify both proximal threats to tropical trees and to guide longer-term management.