Ecological traits and pollination mode associated with dioecious sexual expression in plants are likely to influence their reproductive success and levels of genetic diversity. Dioecy is an uncommon condition in Bromeliaceae. Currently, there is limited information on the reproductive ecology and genetics of dioecious and epiphytic bromeliads. Therefore, we studied the reproductive biology and genetic diversity of the epiphytic and dioecious bromeliad Aechmea mariae-reginae in Costa Rica. Flowering of pistillate and staminate plants in one population showed high synchrony and were pollinated by non-hermit hummingbirds. Sex ratio was biased to males (3.5:1). Fruit set was relatively high (68%) but there was high female reproductive variance (C. V. = 59.7%). The species is capable of parthenocarpic fruit production. Using eight nuclear microsatellite markers and six populations, we found moderate to high levels of genetic variation (HE = 0.571–0.726). Populations showed significant genetic structure (G'ST = 0.385) and Bayesian population assignment grouped them into lowland and montane clusters. Isolated montane populations had slightly lower genetic diversity probably due to lower effective population size caused by biased sex ratios and recent habitat fragmentation that limits long-distance pollinator movements and results in isolation by distance. If habitat fragmentation and isolation persist, populations in montane habitats may be at higher risk of decline and extinction.
The association between the reproductive phenology of epiphytic communities with environmental and ecological factors remains largely unexplored. Because epiphytes depend on environmental moisture, seasonal changes in moisture conditions likely act as the primary determinants of their reproductive timing. We examined whether water limitation or pollinator competition structures the flowering phenologies of an epiphytic community in a seasonal mountain forest in Costa Rica. Additionally, we addressed the environmental factors that might trigger floral induction. Using a 24‐month dataset of bimonthly flowering records from 104 species, we found high seasonality of flowering at the species level but somewhat lower seasonality at the community level. The flowering mid‐dates of most epiphytes, particularly from monocotyledonous species, occurred during the wettest months, as predicted if water limitation structures flowering. The increased moisture and nutrient availability during the rainy season give epiphytes the resources needed to complete floral development and anthesis, and later fruit and seed maturation. The observed flowering pattern of epiphytes coincides with reproductive patterns of terrestrial herbs and shrubs from seasonal tropical ecosystems, and suggests shared constraints to sexual reproduction in both ecological guilds under similar climatic conditions. In contrast, flowering patterns of congeneric epiphytes in the same pollination guild mostly did not follow the expectations of a pollinator competition scenario. Finally, we discuss the possible combined effect of precipitation, temperature, and daily insolation on floral induction of epiphytic plants.
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