Conservation of species interaction networks

Abstract

Recent work has shown that antagonist (e.g. predator-prey food web) and mutualist (e.g. pollinatorplant) network structure can be altered by global environmental change drivers, and that these alterations may have important ecosystem-level consequences. This has prompted calls for the conservation of network structure, but precisely which attributes of webs should be conserved remains unclear. Further, the extent to which network metrics characterise the spatiotemporally-variable dynamic structure of interacting communities is unknown. Here, we summarise the attributes of web structure that are predicted to confer stability or increased function to a system, as these may be of greatest interest to conservation biologists. However, empirical evaluation of these effects is lacking in most cases, and we discuss whether stability is even desirable in all contexts. The incorporation of web attributes into conservation monitoring requires that changes in these attributes can be recorded (sampled) with relative ease. We contrast the sensitivity of metrics to sampling effort, and highlight those (such as nestedness and connectance) that could easily be incorporated into conservation monitoring. Despite our growing understanding of the characteristics of food webs that confer stability and function, numerous practical challenges need to be overcome before the goal of conserving species interaction networks can be achieved.

Flower preferences and pollen transport networks for cavity‐nesting solitary bees: Implications for the design of agri‐environment schemes

“…Connectance describes the fraction of all possible links within a network that are realized, and is a standard measure of food web complexity (Rooney & McCann, 2012; Tylianakis et al., 2010). The higher the level of connectance for a given network size, the greater the degree of generalism of the species involved.…”

“…The degree of nestedness within a network describes the extent to which the plant species interacting with specialist pollinators are a proper subset of the plants interacting with generalists (Bastolla et al., 2009; Tylianakis et al., 2010). A nested structure is believed to enhance the stability of pollination networks by ensuring that, if a specialist pollinator goes extinct, more generalist pollinators still pollinate the plant species that the specialist visited (Memmott, Waser, & Price, 2004; Thébault & Fontaine, 2010).…”

“…The following weighted network metrics were selected as they have been identified as good indicators of stability for pollination networks (Bascompte, Jordano, Melián, & Olesen, 2003; Bastolla et al., 2009; Tylianakis, Laliberté, Nielsen, & Bascompte, 2010): Connectance : The fraction of all possible links within a network that are realized. The higher the level of network connectance, the greater the degree of generalism of the plant and pollinator species involved.…”

“…Higher generality is thought to increase network stability by decreasing the vulnerability of pollinator species to perturbations in the population size of the plant species that they visit. If one or more interactions are disrupted, the impact will be lower for more generalist pollinators that are able to visit many plant species, conferring greater resilience to plant species loss (McCann, 2000; Tylianakis et al., 2010). …”

Focusing Ecological Research for Conservation

“…In turn, biodiversity can be essential for ecosystem stability (MacDougall et al 2013), with stability being maintained by interactions occurring within food webs (Rooney and McCann 2012). Preserving links between interacting species is thus important for ecosystem-level conservation (Tylianakis et al 2009). Paine (1980) coined the term 'trophic cascade', defining it as a series of interactions that ''cascade through the community, transmitted by a chain of strongly interacting links''.…”