Shade coffee farms promote genetic diversity of native trees

Abstract

Coffee is cultivated across 11 million hectares (ha) of land within the world's richest centers of terrestrial biodiversity [1]. In tropical America, coffee is traditionally grown under a diverse canopy of overstory shade trees, which enhances the quality of the coffee farm as a conservation matrix and supports a broad spectrum of pollinators that increase fruit set per bush [2,3,4]. Unlike sun coffee monocultures, shade coffee also sustains a diverse array of vertebrates, including bats and migratory birds, which provide farmers with many ecological services, such as insect predation [5], and may also conserve seed dispersal processes necessary for native tree re-establishment [6]. However, little is known about the capacity of shade coffee farms to maintain gene flow and genetic diversity of remnant tree populations across this common tropical landscape. In this study, we conducted genetic analyses that reveal recent colonization and extensive gene flow of a native tree species in shade coffee farms in Chiapas, Mexico. The high genetic diversity and overlapping deme structure of the colonizing trees also show that traditional coffee farms maintain genetic connectivity with adjacent habitats and can serve as foci of forest regeneration.