Defaunation is associated with increased fine-scale spatial genetic
structure in a small-seeded palm despite high abundances of small-bodied
seed dispersers
Abstract
Anthropogenic pressures such as hunting are increasingly driving the
localized functional extinctions of all or most large and medium-sized
wildlife species in tropical forests, a phenomenon broadly termed
defaunation. Concurrently in these areas, smaller-bodied wildlife
species benefit from factors such as competitive release and experience
population increases. This transformation of the wildlife community can
impact species interactions and ecosystem services such as seed
dispersal and seed-mediated geneflow with far reaching consequences.
Evidence for negative genetic effects following defaunation is
well-documented in large-seeded plants that require large frugivores for
long distance seed dispersal. However, how defaunation affects
small-seeded (< 1.5cm diameter) plants, which are dispersed by
frugivores with a wide range of body-sizes and responses to
anthropogenic threats, is not well understood. To better understand the
reach of defaunation’s impacts on tropical plant communities, we
investigated spatial and genetic patterns in a hyperabundant
small-seeded palm, Euterpe precatoria in three sites representing
distinct defaunation levels. We found significantly higher fine-scale
spatial genetic structure among nearest-neighbor seedlings in the
defaunated site and in the recovering, partially defaunated site
relative to the faunally-intact site. Defaunation was associated with
shorter distances between seedlings and adults and lower genetic
distance between adult and seedling cohorts. No effects were detected on
inbreeding and genetic diversity; however, we caution that trends we
detected indicate that defaunation influences the spatial distribution
of genetic variation even in small-seeded plants that inherently have a
broad suite of seed dispersal agents, and this could lead to negative
downstream effects on genetic diversity.