Coexistence of species of vanilla and implications for harvesting
Species coexistence mechanisms include a broad range of strategies to occupy different ecological niches. In diverse tropical rain forests plant species are strongly limited in their use of biotic and abiotic resources because of competition. Plant abiotic resource partition is visible through water and nutrient uptake strategies, meanwhile biotic interactions with endophytes and pollinators may reflect biotic resource partition. We studied four coexisting native Vanilla species in the Choco Wet Forest (Western Colombia) in order to understand which are the main determinants for its coexistence. We analyzed whether ecological niches of theses four species overlap and if fruit harvesting of native populations is long-term sustainable. Vanilla species were studied in eight sites. We recorded species distribution, reproductive monthly phenology during a year, floral morphology, breeding system, functional traits, floral visitors, pathogens and microorganisms associated with roots.
Our results showed that the four Vanilla species (V. planifolia, V. odorata, V. cribbiana, and V. trigonocarpa) presented different mechanisms to avoid direct competition among them for resources from top to bottom. Species occurred in the same locations with a subtle differentiation among habitats. Leaf functional traits were segregated among species and differences were maintained along a plant vertical stratification. Floral morphology, aperture, receptivity and flowering peaks were differentiated among species. Plant-pollinators and plant-microorganisms networks were well defined for each species. Fruit production was scarce during a year of monitoring.
Niche segregation of Vanilla species through biotic and abiotic resource partition prevent competitive exclusion and hybridization, however fruit productions is very low. Species in such conditions will be very vulnerable to fruit harvesting. Vanilla species showed a very low fruit production and a narrow niche overlapping even when they coexist in the same locations. Our study indicates that Vanilla species will be face a population bottleneck if fruit harvesting is not controlled.