Trophic disruption: a meta‐analysis of how habitat fragmentation affects resource consumption in terrestrial arthropod systems

Abstract

Habitat fragmentation is a complex process that affects ecological systems in diverse ways, altering everything from population persistence to ecosystem function. Despite widespread recognition that habitat fragmentation can influence food web interactions, consensus on the factors underlying variation in the impacts of fragmentation across systems remains elusive. In this study, we conduct a systematic review and meta-analysis to quantify the effects of habitat fragmentation and spatial habitat structure on resource consumption in terrestrial arthropod food webs. Across 419 studies, we found a negative overall effect of fragmentation on resource consumption. Variation in effect size was extensive but predictable. Specifically, resource consumption was reduced on small, isolated habitat fragments, higher at patch edges, and neutral with respect to landscapescale spatial variables. In general, resource consumption increased in fragmented settings for habitat generalist consumers but decreased for specialist consumers. Our study demonstrates widespread disruption of trophic interactions in fragmented habitats and describes variation among studies that is largely predictable based on the ecological traits of the interacting species. We highlight future prospects for understanding how changes in spatial habitat structure may influence trophic modules and food webs.

Species interactions regulate the collapse of biodiversity and ecosystem function in tropical forest fragments

“…The main exceptions are studies dealing with food webs and other interactions between different trophic levels (e.g., Galetti et al 2013, Martinson andFagan 2014). Our results suggest that interactions among species within the same trophic level can play an important, yet overlooked, role in regulating the effects of fragmentation on biodiversity and ecosystem function.…”

Spatially Heterogeneous Perturbations Homogenize the Regulation of Insect Herbivores

“…Despite clear experimental evidence of the impact of top predators on grassland insect herbivores (for a review see Schmitz 2010), empirical findings generally emphasize bottom-up control from plants (Haddad et al 2009;Borer et al 2012;Rzanny et al 2013). Our results confirm the well-documented sensitivity of top predators to landscape alteration (Purvis et al 2000;Martinson and Fagan 2014) but suggest that for grassland insect communities, the decline of top predators does not necessarily lead to predator-mediated effects on herbivore communities. However, recent studies have shown that the regulatory effect of top predators on insects can be context dependent as a function of seasonality (Gratton and Denno 2003), wind speed (Barton 2014), and especially temperature (Hoekman 2010;Shurin et al 2012;Barton and Ives 2014).…”

“…7; and strong: DAIC 1 10 (after Burnham and Anderson 2002 control of insect primary consumers, from mixed predator resource to unidirectional resource regulation. Past work had made the connection between habitat fragmentation and the potential disruption of trophic control (Nelson et al 2013;Martinson and Fagan 2014). However, mechanistic linkages with multiple stressors have been needed to accurately describe potential effects of global change, which are typically multivariate in nature (i.e., simultaneous alterations to resource, consumers, and spatial dynamics).…”

“…These effects are especially acute for insect herbivores, which influence numerous ecological and evolutionary processes, including functional attributes relating to plant production and pollination (Crawley 1989;Branson et al 2006;Schmitz 2010;Agrawal et al 2012;Silliman et al 2013;Borer et al 2014). There is widespread evidence for anthropogenic-based changes to insect herbivore communities, with signals including reduced species richness, invasion, outbreaks, and selection toward generalist feeding strategies (Tscharntke and Brandl 2004;Branson et al 2006;Clavel et al 2010;Martinson and Fagan 2014). What remains unclear are the main drivers of these changes, given that human disturbances (e.g., habitat loss, stand perturbation) may directly affect herbivore diversity and composition but also do so indirectly via trophically mediated effects on plants and predators (Halpern et al 2005;Shurin et al 2012;Rzanny et al 2013).…”

Spatial and temporal genetic structure at the fourth trophic level in a fragmented landscape

“…This is because with increasing trophic level, the resource pool becomes sparse and locally unstable [1][2][3]. Parasitoids live at the third and fourth trophic levels and are an important part of virtually all insect communities [4].…”