One major challenge in understanding how biodiversity is organized is finding
out whether communities of competing species are shaped exclusively by
species-level differences in ecological traits (niche theory), exclusively
by random processes (neutral theory of biodiversity), or by both processes
simultaneously. Communities of species competing for a pulsed resource are a
suitable system for testing these theories: due to marked fluctuations in
resource availability, the theories yield very different predictions about
the timing of resource use and the synchronization of the population
dynamics between the competing species. Accordingly, we explored mechanisms
that might promote the local coexistence of phytophagous insects (four
sister species of the genus Curculio) competing for oak
acorns, a pulsed resource.
We analyzed the time partitioning of the exploitation of oak acorns by the
four weevil species in two independent communities, and we assessed the
level of synchronization in their population dynamics. In accordance with
the niche theory, overall these species exhibited marked time partitioning
of resource use, both within a given year and between different years owing
to different dormancy strategies between species, as well as distinct
demographic patterns. Two of the four weevil species, however, consistently
exploited the resource during the same period of the year, exhibited a
similar dormancy pattern, and did not show any significant difference in
their population dynamics.
The marked time partitioning of the resource use appears as a keystone of the
coexistence of these competing insect species, except for two of them which
are demographically nearly equivalent. Communities of consumers of pulsed
resources thus seem to offer a promising avenue for developing a unifying
theory of biodiversity in fluctuating environments which might predict the
co-occurrence, within the same community, of species that are ecologically
either very similar, or very different.
Publisher: Public Library of Science
Date Published: 21-March-2011
Author(s): Venner S., Pélisson P., Bel-Venner M., Débias F., Rajon E., Menu F.