Movement in the Matrix: Pollination and Dispersal Processes in a Tropical Coffee and Forest Landscape Mosaic.

Abstract

Despite efforts at conservation, tropical forests continue to face destruction, threatening many tropical tree species, especially those that depend on a narrow guild of pollen and seed dispersers. My dissertation investigates essential pollen and seed dispersal processes for Miconia affinis (Melastomataceae), a native bee-pollinated tree that primarily inhabits tropical forests, but can be found as a colonist in shade coffee systems. I quantified bee diversity, foraging behavior, and pollination success of M. affinis in different coffee plantations and determined that honeybee visitation was significantly higher and ambient fruit set was significantly lower for M. affinis in coffee habitats compared to forest habitats. I found that native bees and exotic bees exhibited contrasting foraging patterns in response to coffee management style and foraging scale, and that native bees were more abundant and diverse in coffee farms with greater overstory tree diversity. Using eight microsatellite loci, I conducted molecular analyses that revealed recent colonization of coffee fields by M. affinis from four sources. Levels of allelic richness and heterozygosity in forest and coffee habitats were high. Forest populations showed strong spatial genetic structure at the 100 and 200m distance class, while no spatial genetic structure was detected in the coffee habitats. Molecular-based pollen dispersal analyses revealed long-distance pollen movement across the landscape (up to 1800 m) with extensive dispersal between coffee and forest habitats. Overall, these results provide strong evidence that shade coffee farms can serve as permeable habitat matrices for critical native plant pollinators and seed dispersers.