Data from: Extinction-driven changes in frugivore communities on oceanic islands

Global change and human expansion have resulted in many species
extinctions worldwide, but the geographic variation and determinants of
extinction risk in particular guilds still remain little explored. Here,
we quantified insular extinctions of frugivorous vertebrates (including
birds, mammals and reptiles) across 74 tropical and subtropical oceanic
islands within 20 archipelagos worldwide and investigated extinction in
relation to island characteristics (island area, isolation, elevation and
climate) and species’ functional traits (body mass, diet and ability to
fly). Out of the 74 islands, 33 islands (45%) have records of frugivore
extinctions, with one third (mean: 34%, range: 2–100%) of the
pre-extinction frugivore community being lost. Geographic areas with more
than 50% loss of pre-extinction species richness include islands in the
Pacific (within Hawaii, Cook Islands and Tonga Islands) and the Indian
Ocean (Mascarenes, Seychelles). The proportion of species richness lost
from original pre-extinction communities is highest on small and isolated
islands, increases with island elevation, but is unrelated to temperature
or precipitation. Large and flightless species had higher extinction
probability than small or volant species. Across islands with extinction
events, a pronounced downsizing of the frugivore community is observed,
with a strong extinction-driven reduction of mean body mass (mean: 37%,
range: -18–100%) and maximum body mass (mean: 51%, range: 0–100%). The
results document a substantial trophic downgrading of frugivore
communities on oceanic islands worldwide, with a non-random pattern in
relation to geography, island characteristics and species’ functional
traits. This implies severe consequences for ecosystem processes that
depend on mutualistic plant-animal interactions, including ecosystem
dynamics that result from the dispersal of large-seeded plants by
large-bodied frugivores. We suggest that targeted conservation and
rewilding efforts on islands are needed to halt the defaunation of large
and non-volant seed dispersers and to restore frugivore communities and
key ecological interactions.