The Population and Ecological Genetic Effects of Habitat Fragmentation

Abstract

Maintaining intraspecific variation is important for populations’ long-term success and is increasingly being recognized as an important conservation goal. Populations in anthropogenically fragmented habitats may lose variation rapidly via genetic drift, particularly in small fragments with a high ratio of edge to interior habitat. We studied the population and ecological genetic effects of habitat fragmentation on both a foundation plant, Spartina patens, and a dependent herbivore, Tumidagena minuta, using a naturally fragmented, salt marsh model system. We employed microsatellite marker analyses to estimate various measures of genetic variation, including allelic richness and heterozygosity, and to estimate the strength of genetic drift using estimates of effective population size (Ne). To achieve this, we developed a new program to estimate Ne and developed new markers for S. patens from genome sequence data. We found lower S. patens genetic variation and lower T. minuta Ne near the S. alterniflora edges, indicating that T. minuta experience stronger genetic drift near edges. These findings reinforce the importance of habitat patch shape in influencing populations.