INVESTIGADORES
SALVO Silvia Adriana
artículos
Título:
Forest fragmentation reduces parasitism via species loss at multiple trophic levels
Autor/es:
FENOGLIO, M. S.; SRIVASTAVA, D.; VALLADARES, G. R.; CAGNOLO, L.; SALVO, A.
Revista:
ECOLOGY
Editorial:
ECOLOGICAL SOC AMER
Referencias:
Lugar: 93:24072420; Año: 2012 vol. 93 p. 2047 - 2420
ISSN:
0012-9658
Resumen:
Although there is accumulating evidence from artificially assembled commu-
nities that reductions of species diversity result in diminished ecosystem functioning, it is not
yet clear how real-world changes in diversity affect the flow of energy between trophic levels in
multi-trophic contexts. In central Argentina, forest fragmentation has led to species loss of
plants, herbivore and parasitoid insects, decline in trophic processes (herbivory and
parasitism), and food web contraction. Here we examine if and how loss of parasitoid species
following fragmentation causes decreased parasitism rates, by analyzing food webs of leaf
miners and parasitoids from 19 forest fragments of decreasing size. We asked three questions:
Do reductions in parasitoid richness following fragmentation directly or indirectly affect
parasitism rate? Are changes in community parasitism rate driven by changes in the parasitism
rate of individual leaf miner species, or changes in leaf miner composition, or both? Which
traits of species determine the effects of food web change on parasitism rates? We found that
habitat loss initiated a bottom-up cascade of extinctions from plants to leaf miners to
parasitoids, with reductions in parasitoid richness ultimately driving decreases in parasitism
rates. This relationship between parasitoid richness and parasitism depended on changes in the
relative abundance (but not occurrence) of leaf miners such that parasitoid-rich fragments
were dominated by leaf miner species that supported high rates of parasitism. Surprisingly, we
found that only a small subset of species in the food web could account for much of the
increase in parasitism with parasitoid richness: lepidopteran miners that attained exceptionally
high densities in some fragments and their largely specialist parasitoids. How specialized a
parasitoid is, and the relative abundance of leaf miners, had important effects on the diversity
parasitism rate relationship, but not other leaf miner traits including trophic breadth, body
size, and mine shape. Our results show that a full understanding of the functional
consequences of perturbations and species loss requires both a multi-trophic perspective
and a trait-based approach, which together capture some of the biological complexity of
natural systems.