Habitat fragmentation disrupts a plant-disperser mutualism in the temperate forest of South America

Abstract

The disruption of dispersal mutualisms may have profound consequences for seedling recruitment, plant demography, and population persistence, with potential cascading effects throughout the rest of the community. In the temperate forest of South America, the seeds of the mistletoe Tristerix corymbosus, a proposed key species, are dispersed solely by the endemic marsupial Dromiciops gliroides. In three sites that included two contrasting habitats, one fragmented and the other not, we assessed effects of forest fragmentation on marsupial abundance, fruit removal, seed dispersal and seedling recruitment rates. We also compared the age structure of mistletoe populations between fragmented and non-fragmented forest habitats. Fragmentation affected negatively marsupial abundance, fruit removal, seed dispersal, and seedling recruitment. The local extinction of D. gliroides was associated with the complete disruption of mistletoe seed dispersal. Mistletoe populations in fragmented forests exhibited a deficiency in juveniles because of a lack of recruitment. Thus, effects of forest fragmentation on this dispersal mutualism have clear demographic consequences, which may compromise the survival of mistletoe populations.