Plant Mating Systems in Small Populations

Habitat fragmentation and degradation are causing population declines in many species. In seed plants, mating patterns are expected to be influenced by both historical and contemporary population sizes and affect population viability. Historical population sizes influence overall genetic variation and accumulation of genetic load. Contemporary population size and density affect mating patterns as well as the degree of pollen limitation of seed production because of their effects on interactions with pollinators. Several ecological and genetic effects of small population size affect the fitness consequences of self-fertilization and favor reproductive assurance through autonomous self-pollination. Comparative and experimental studies demonstrate that selection on traits influencing the mating system can be strong under mate and pollen limitation and that evolutionary responses can be rapid given sufficient genetic variation. We highlight the prospects of using experimental evolution and artificial selection for understanding the interactions among population size, mating system, and population viability.