Robustness of a meta‐network to alternative habitat loss scenarios

Abstract

Studying how habitat loss affects the tolerance of ecological networks to species extinction (i.e. their robustness) is key for our understanding of the influence of human activities on natural ecosystems. With networks typically occurring as local interaction networks interconnected in space (a meta-network), we may ask how the loss of specific habitat fragments affects the overall robustness of the meta-network. To address this question, for an empirical meta-network of plants, herbivores and natural enemies we simulated the removal of habitat fragments in increasing and decreasing order of area, age and connectivity for plant extinction and the secondary extinction of herbivores, natural enemies and their interactions. Meta-network robustness was characterized as the area under the curve of remnant species or interactions at the end of a fragment removal sequence. To pinpoint the effects of fragment area, age and connectivity, respectively, we compared the observed robustness for each removal scenario against that of a random sequence. The meta-network was more robust to the loss of old (i.e. long-fragmented), large, connected fragments than of young (i.e. recently fragmented), small, isolated fragments. Thus, young, small, isolated fragments may be particularly important to the conservation of species and interactions, while contrary to our expectations larger, more connected fragments contribute little to meta-network robustness. Our findings highlight the importance of young, small, isolated fragments as sources of species and interactions unique to the regional level. These effects may largely result from an unpaid extinction debt, whereby younger fragments are likely to lose species over time. Yet, there may also be more long-lasting effects from cultivated lands (e.g. water, fertilizers and restricted cattle grazing) and network complexity in small, isolated fragments. Such fragments may sustain important biological diversity in fragmented landscapes, but maintaining their conservation value may depend on adequate restoration strategies.

Effects of habitat destruction on coevolving metacommunities

“…This may also be true in networks with long distance dispersal, as the ability to colonise habitats further away (rather than the nearest patches only as in this study) has been shown to increase the extinction thresholds (Gawecka and Bascompte, 2021). Finally, we postulate that network rewiring (which has not been considered here for simplicity) may further buffer the effects of habitat loss on both the ecological and coevolutionary dynamics, as the flexibility of interaction partners may increase species' persistence (e.g., Kaiser-Bunbury et al, 2010;Ramos-Jiliberto et al, 2012;Tylianakis and Morris, 2017;Santos et al, 2021).…”

Forest structure and heterogeneity increase diversity and alter composition of host–parasitoid networks

“…It was contrary to our expectations that more specific parasitoids comprise more of the metanetwork core than generalists, given that generalists are more frequently encountered due to greater niche breadth (Kassen, 2002; Robinson & Strauss, 2018). Several studies have highlighted the importance of rare or unique parasitoids in stabilising metanetworks (Santos et al, 2020), but the importance of more specific parasitoids in our analyses of metanetwork interactions warrants further study. Moreover, more abundant hosts may support more specialist parasitoids due to the stability of hosts as a resource and sensitivity of specialist parasitoids to fluctuations in host populations (Cagnolo et al, 2009; Holzchuh et al, 2010).…”

Effects of habitat destruction on coevolving metacommunities

“…Such network rewiring has been shown to change network structure (Loeuille & Loreau, 2005; Suweis et al, 2013), and this is expected to alter the eco‐evolutionary dynamics. We postulate that interaction rewiring may buffer the effects of habitat loss, as the flexibility of interaction partners may increase species' persistence (Kaiser‐Bunbury et al, 2010; Ramos‐Jiliberto et al, 2012; Santos et al, 2021; Tylianakis & Morris, 2017).…”