Dados do Trabalho

Título:

BREAKDOWN OF PREDATOR-PREY INTERACTION NETWORKS IN AMAZONIAN FOREST FRAGMENTS

Resumo:

Habitat loss and fragmentation are the main underlying causes of the current biodiversity crisis. As populations decline within fragments, their interactions become less frequent and species may become functionally extinct, disrupting local food webs. Here we use data from field surveys of forest vertebrates, models, and network analysis to investigate how habitat fragmentation in the Brazilian Amazonia affected the structure of vertebrate predator-prey interaction networks. Analyzing the networks generated for 37 sites with varying forest area, we found that network complexity decayed non-linearly with the decrease in forest area. In sites with little remaining forest (< 100 ha), networks had only a small fraction of the interactions likely to happen in continuous forest sites. The mean number of prey species per predator in sites with greater forest area was twice as large as that in small forest fragments, and whereas species were linked on average to three potential predators in large fragments, in small ones, species had one or no predator left. In fact, several species had no potential predator in about one third of the sites where they had been recorded. Using extinction simulations, we also show that the networks in small fragments are not only the result of subsampling of the networks in the continuous area. Instead, they host idiosyncratic networks with atypical trophic structure. Our findings thus show that as fragment size reduces the system cannot retain the structural properties of networks in the continuous forest and becomes dysfunctional. The fact that many species lack predators in small forest fragments suggests that top-down regulation has been severed, which may have consequences for vegetation structure. We argue that besides maintaining diversity, protecting large forest fragments is necessary to preserve the structural complexity of interaction networks and thus the functional properties of ecological systems in tropical forests.

Financiamento:

FAPESP: #2019/25478-7

Área

Ecologia