Habitat disturbance selects against both small and large species across varying climates

Abstract

Global extinction drivers, including habitat disturbance and climate change, are thought to affect larger species more than smaller species. However, it is unclear if such drivers interact to affect assemblage body size distributions. We asked how these two key global change drivers differentially affect the interspecific size distributions of ants, one of the most abundant and ubiquitous animal groups on earth. We also asked whether there is evidence of synergistic interactions and whether effects are related to species’ trophic roles. We generated a global dataset on ant body size from 333 local ant assemblages collected by the authors across a broad range of climates and in disturbed and undisturbed habitats. We used head length (range: 0.22–4.55 mm) as a surrogate of body size and classified species to trophic groups. We used generalized linear models to test whether body size distributions changed with climate and disturbance, independent of species richness. Our analysis yielded three key results: 1) climate and disturbance showed independent associations with body size; 2) assemblages included more small species in warmer climates and fewer large species in wet climates; and 3) both the largest and smallest species were absent from disturbed ecosystems, with predators most affected in both cases. Our results indicate that temperature, precipitation and disturbance have differing effects on the body size distributions of local communities, with no evidence of synergistic interactions. Further, both large and small predators may be vulnerable to global change, particularly through habitat disturbance.

Grazing and resource availability control soil nematode body size and abundance–mass relationship in semi‐arid grassland

“…In the low‐OM soil, the higher mean body mass under grazing did not result in a clear shift in individual size distribution, because grazing had increased the abundance of nematodes of intermediate size (groups 3–7) and reduced that of both the smallest and some of the largest (groups 1 and 9–10, respectively, Supporting Information Figure S4). Comparable losses at both extremes of body size were shown in ant communities under habitat disturbance (Gibb et al., ). The size distribution in a nematode community has implications for soil functioning; for example, small bacterial feeders tend to mineralize more nitrogen per unit of body weight than larger species (Ferris, Venette, van der Meulen, & Lau, ).…”

Effects of increasing aridity and chronic anthropogenic disturbance on seed dispersal by ants in Brazilian Caatinga

“…Highest quality seed dispersal services are typically provided by large‐bodied ant species because they readily collect seeds and transport them over large distances (Andersen & Morrison, ; Leal, Correia Neto Lima, Oliveira, Andersen, & Leal, ). Large ant species are especially sensitive to disturbance (Gibb et al., ; Leal, Andersen, & Leal, ), and this can result in severe reductions in the quality of seed dispersal services in disturbed habitats (Almeida et al., ; Gove, Majer, & Dunn, ; Leal, Andersen, & Leal, ; Ness, Bronstein, Andersen, & Holland, ). Although smaller insects are considered more sensitive to high temperatures through desiccation (Baudier, Mudd, Erickson, & O'Donnell, ; Kühsel, Brückner, Schmelzle, Heethoff, & Blüthgen, ), recent studies have found that the most sensitive ants to climate change are in fact the largest (Andrew, Miller, Hall, Hemmings, & Oliver, ; Gibb et al., ).…”

“…Large ant species are especially sensitive to disturbance (Gibb et al., ; Leal, Andersen, & Leal, ), and this can result in severe reductions in the quality of seed dispersal services in disturbed habitats (Almeida et al., ; Gove, Majer, & Dunn, ; Leal, Andersen, & Leal, ; Ness, Bronstein, Andersen, & Holland, ). Although smaller insects are considered more sensitive to high temperatures through desiccation (Baudier, Mudd, Erickson, & O'Donnell, ; Kühsel, Brückner, Schmelzle, Heethoff, & Blüthgen, ), recent studies have found that the most sensitive ants to climate change are in fact the largest (Andrew, Miller, Hall, Hemmings, & Oliver, ; Gibb et al., ). This might be because large ants require more resources and take longer to mature, thus reducing their adaptive capacity (Gibb et al., ; McCain & King, ; Savage, Gillooly, Brown, West, & Charnov, ).…”

Habitat‐contingent responses to disturbance: impacts of cattle grazing on ant communities vary with habitat complexity

“…We found this generally to be the case, with similar results for ant abundance, species richness and composition. This suggests that restricting analysis to larger species might even provide a more sensitive measure of ant responses to grazing than does analysis of entire communities, which reflects a higher sensitivity of large ants to disturbance (Ness et al 2004;H. Notably, analysis of only larger species found dominant Dolichoderinae and specialist predators to be increasers and FIG.…”

“…This often puts ants and other invertebrates in the "too hard" basket for land managers. The latter is especially promising because large ants are especially sensitive to disturbance (Ness et al 2004, H. Gibb et al, 2018 and are much more readily sorted to species and identified to genus than are small ants, especially by a nonspecialist. The latter is especially promising because large ants are especially sensitive to disturbance (Ness et al 2004, H. Gibb et al, 2018 and are much more readily sorted to species and identified to genus than are small ants, especially by a nonspecialist.…”