Pollen dispersal and genetic diversity of Yucca valida (Asparagaceae), a plant involved in an obligate pollination mutualism

Abstract In insect-pollinated plants, gene flow through pollen depends on the behaviour of pollinators when moving pollen, as well as the spatial distribution of the plants. For the perennial species Yucca valida, we evaluated gene flow mediated by its obligate pollinator, the yucca-moth Tegeticula baja. We also estimated genetic diversity and population structure throughout the plant’s geographical distribution. Using nuclear microsatellites, we genotyped 405 individuals, representing 105 trees and progenies from 15 plants (300 seedlings). We estimated outcrossing rate, pollen donors, dispersion distance and genetic autocorrelation index, as well as diversity and differentiation indexes. We found that Y. valida has a mostly outcrossing mating system. Gene flow through pollen occurs over short distances (42 m) within a small reproductive neighbourhood (1.4 ha) where individuals are genetically related. Each mother plant’s progeny has at least 2.8 pollen donors. Despite the inbreeding detected, interaction among yucca life-history traits may maintain high levels of genetic diversity and low differentiation among Y. valida populations. The spatial scale at which gene flow operates is essential in understanding the distribution of genetic variation within and between populations.