Biological invasion modifies the co‐occurrence patterns of insects along a stress gradient

Abstract

Summary Biological invasions have become one of the most important drivers of biodiversity loss and ecosystem change world‐wide. However, it is still unclear how invasions may interact with local abiotic stressors, which are expected to increase as global change intensifies. Furthermore, we know little about the response to biological invasions of insects, despite their disproportionate contribution to global animal biodiversity. The aim of the present work is to investigate the impact of an invasive aquatic insect on the co‐occurrence patterns of native species of insects along a salinity gradient, and determine which assembly rules are driving these patterns. First, we characterised the habitat specialisation and functional niches of each species from physiological and biological traits, respectively, and their degree of overlap. Second, we used field data to compare the co‐occurrence patterns of native and invasive species in invaded and non‐invaded areas of southern Iberia and northern Morocco. Finally, we tested if habitat filtering or niche differentiation assembly rules mediate their co‐occurrence. In non‐invaded areas, habitat filtering drives habitat segregation of species along the salinity gradient, with a lower contribution of niche differentiation. The presence of the invasive insect modifies the distribution and co‐occurrence patterns of native species. In invaded areas, niche differentiation seems to be the main mechanism to avoid competition among the invasive and native species, enabling coexistence and resource partitioning. The combined study of functional niche similarity and abiotic stressor tolerance of invasive and native species can improve our understanding of the effects of invasive species along abiotic stress gradients. This approach may increase our capacity to predict the outcomes of biological invasion in a global change context. A http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.12884/suppinfo is available for this article.

Competition between co‐occurring invasive and native consumers switches between habitats

“…At high abiotic stress in intertidal horizontal habitats, however, the trophic niche of O. edulis became more δ 15 N enriched in the presence of M. gigas , which may indicate an increase in trophic level, while M. gigas' trophic niche remained stable. Contrary to the theory that niche partitioning facilitates coexistence of competitors at higher abiotic stress levels (Bulleri et al, ; Carbonell et al, ), changes in trophic niches in this context were not indicative of trophic re‐organization nor of individual niche specialization (Britton et al, ; Costa‐Pereira & Rudolf, ). Therefore, it is unlikely that exploitative competition was a driving factor in intertidal habitats.…”

“…Here, we have shown that, in the presence of a morphologically similar competitor, invasion success was determined by abiotic stress, and that surface topography drives differences in biotic interaction type. Specifically, this study has shown that niche partitioning and facilitation were primarily driven by surface topography rather than abiotic stress (Bruno et al, 2003;Carbonell et al, 2017) and suggests that differences in ecological niches, such as those created by orientation of substratum is an under-rated factor in species interactions and should be included in future studies aiming to clarify the role of invasive competitors.…”

“…Model outputs with 95% credible intervals are given before a summarized increase or decrease and probability. Overall trends towards a more benthic or pelagic diet are indicated by asterisks (Jackson et al, 2012;Vander Zanden, Casselman, & Rasmussen, 1999 higher abiotic stress levels (Bulleri et al, 2016;Carbonell et al, 2017), changes in trophic niches in this context were not indicative of trophic re-organization nor of individual niche specialization (Britton et al, 2018;Costa-Pereira & Rudolf, 2018). Therefore, it is unlikely that exploitative competition was a driving factor in intertidal habitats.…”

“…Abiotic stressors, such as desiccation or shear stress, can enhance the negative impact of invasions when occurring at unprecedented rates or magnitude (Macdougall & Turkington, ). However, competitive interactions can also be mitigated by abiotic stress, which enables resource partitioning that may result in the coexistence of species with similar ecological niches (Carbonell et al, ; Krassoi et al, ). Biological interactions are further modified by habitat heterogeneity, which determines the strength of competitive effects based on the ecological niche requirement of invasive and native competitors (Bando, ; Bulleri, Bruno, Silliman, & Stachowicz, ).…”

“…Abiotic stressors, such as desiccation or shear stress, can enhance the negative impact of invasions when occurring at unprecedented rates or magnitude (Macdougall & Turkington, 2005). However, competitive interactions can also be mitigated by abiotic stress, which enables resource partitioning that may result in the coexistence of species with similar ecological niches (Carbonell et al, 2017;Krassoi et al, 2008).…”