Floral display and mating patterns within populations of the neotropical epiphytic orchid, Laelia rubescens (Orchidaceae)

Pollinator behavior plays a central role in determining patterns of pollen-mediated gene movement in zoophilous angiosperms. A species' floral display can strongly influence the behavior of its pollinators and thereby affect its evolutionary pathway. We used paternity analysis to directly measure and describe mating patterns within 15 populations of the epiphytic orchid, Laelia rubescens, in Costa Rican dry forest. Strict correlated mating by orchids allows inference of the precise multilocus diploid genotype of the pollen parents. Our data show that mean effective population sizes were small (11.2 in 1999 and 11.8 in 2000) relative to the number of flowering genets (63 and 56, respectively). Fewer genets were reproductively successful as females than males. The relationship between reproductive success (RS) and floral display within three cluster size classes was consistent between years, with large (> 30 inflorescences) and small (<= 10 inflorescences) clusters often having significantly lower RS than expected, while the RS of medium-sized clusters (11-30 inflorescences) often significantly exceeded expectations. Paternity analysis allowed us to take advantage of the pollination biology of L. rubescens to provide unusually detailed insights into mating patterns, pollen-mediated gene movement and RS for populations of this epiphytic orchid, an herbaceous perennial, distributed in three-dimensional space.