Frugivore-mediated seed dispersal in fragmented landscapes: Compositional and functional turnover from forest to matrix

Seed dispersal by frugivores is a fundamental function for plant community
dynamics in fragmented landscapes, where forest remnants are typically
embedded in a matrix of anthropogenic habitats. Frugivores can mediate
both connectivity among forest remnants and plant colonization of the
matrix. However, it remains poorly understood how frugivore communities
change from forest to matrix due to the loss or replacement of species
with traits that are less advantageous in open habitats, and whether such
changes ultimately influence the composition and traits of dispersed
plants via species interactions. Here, we close this gap by using a unique
dataset of seed-dispersal networks that were sampled in forest patches and
adjacent matrix habitats of seven fragmented landscapes across Europe. We
found a similar diversity of frugivores, plants and interactions
contributing to seed dispersal in forest and matrix, but a high turnover
(replacement) in all these components. The turnover of dispersed seeds was
smaller than that of frugivore communities because different frugivore
species provided complementary seed dispersal in forest and matrix.
Importantly, the turnover involved functional changes towards larger and
more mobile frugivores in the matrix, which dispersed taller,
larger-seeded plants with later fruiting periods. Our study provides a
trait-based understanding of frugivore-mediated seed dispersal through
fragmented landscapes, uncovering non-random shifts that can have
cascading consequences for the composition of regenerating plant
communities. Our findings also highlight the importance of forest remnants
and frugivore faunas for ecosystem resilience, demonstrating a high
potential for passive forest restoration of unmanaged lands in the matrix.