Effects of habitat loss on the plant–flower visitor network structure of a dune community

Abstract

Pollination is a valuable ecosystem service, and plant–pollinator interactions in particular are known to play a crucial role in conservation and ecosystem functioning. These mutualisms, like other ecological interactions, are currently threatened by different drivers of global change, mainly habitat loss, fragmentation, or modification of its quality. Most studies so far have focused on the impact of such disturbances on particular species interactions and we thus need more empirical evidence on the responses at a community‐level. Here we evaluated how habitat loss influenced the pattern of interactions between plants and their flower visitors in a coastal dune marshland community. Using data from four years (2008–2011), we assessed the effect of a large disturbance in the area (occurring in 2010) that represented the loss of more than 50% of the vegetation cover. We found a considerable decrease in species richness and abundance of flower visitors, which resulted in a lower number of interactions after the disturbance. Not all functional groups, however, responded similarly. Contrary to the expected from previous findings, bees and wasps were less negatively influenced than beetles, flies and ants, possibly due to their higher movement capacity. Species interactions in the community were more specialized after habitat loss, resulting in a lower level of network nestedness and a higher modularity. At a species level, the number of flower visitors per plant decreased after the disturbance, and plants were visited by less abundant flower visitors. Our findings lead us to predict that the overall plant–flower visitor network became less robust and resilient to future perturbations. However, the fact that each functional group responds distinctly to disturbances makes it more difficult to foresee the final consequences on community composition and ecosystem functioning.

Interaction networks of avian mixed‐species flocks along elevation in the tropical Andes

“…Using networks to represent community structure of mixed‐species flocks and monitoring changes in flocking assemblages and species interactions are promising avenues for future biodiversity studies in the tropical Andes (Gilman et al ), especially where forested areas are being lost at a fast rate (Urrutia and Vuille , Anderson et al ). For example, the higher connectivity and low modularity in mutualistic networks have been found to impart stability to the interacting community, potentially resulting in more resilient networks to species loss (Thébault and Fontaine , Traveset et al ). By increasing the number, strength and symmetry of pairwise interactions among nodes in a network, the possibility of any given node to be loss by the loss of any of the species associated to it decreases (Okuyama and Holland ).…”

Hummingbird–Plant Interactions Are More Specialized in Forest Compared to Coffee Plantations

“…We built one hummingbird-pollen type interaction network for each of the 19 sites and one for the entire agricultural ecosystem by pooling all sites into a single large network. To measure interaction specialization, we used a standardized index for calculating niche partitioning of a complex network called H 2 ' [41], also referred to as a measure of network specificity [42]. The H 2 ' metric is the standardized two-dimensional Shannon entropy for interactions rather than species [41,43].…”

“…We also calculated hummingbird species specialization using the metric d', the species-level equivalent of the metric H 2 ' [41], as the metric d' is also a quantitative measure of species specialization, or specificity, [42]. Like H 2 ', a larger d' indicates greater species specialization.…”

Agricultural intensification drives changes in hybrid network robustness by modifying network structure

“…We specifically use the term "hybrid" here to mean networks that combine two or more types of interactions, like antagonisms (À/+) and mutualisms (+/+) (as in Mougi & Kondoh 2014;Suweis et al 2014). Although it has been established that anthropogenic change alters the structure of food webs and bipartite networks (Tylianakis et al 2007;Burkle et al 2013;Spiesman & Inouye 2013;Albrecht et al 2014;Weiner et al 2014;Vanbergen et al 2014;de Ara ujo et al 2015;Tylianakis & Morris 2017;Traveset et al 2018), there is currently minimal empirical data on the response of hybrid networks to environmental disturbance.…”