Invasive spread in meta‐food‐webs depends on landscape structure, fertilization and species characteristics

Abstract

Land use change and biological invasions collectively threaten biodiversity. Yet, few studies have addressed how altering the landscape structure and nutrient supply can promote biological invasions and particularly invasive spread (the spread of an invader from the place of introduction), or asked whether and how these factors interact with biotic interactions and invader properties. We here bridge this knowledge gap by providing a holistic network‐based approach. Our approach combines a trophic network model with a spatial network model allowing us to test which combinations of abiotic and biotic factors can facilitate invasions and in particular invasive spread in food webs. We numerically simulated 6300 single‐species invasions in clustered and random landscapes at different levels of nutrient supply. In total, our simulation experiment yielded 69% successful invasions – 71% in clustered landscapes and 66% in random landscapes, with the proportion of successful invasions increasing with nutrient supply. However, invasive spread was generally higher in random than in clustered landscapes. The latter can facilitate invasive spread within a habitat cluster, but prevent invasive spread between clusters. Low nutrient levels generally prevented the establishment of invasive species and their subsequent spread. However, successful invaders could have more severe impacts as they contribute more to total biomass density and species richness under such conditions. Good dispersal abilities drive the broad‐scale spread of invasive species in fragmented landscapes. Our approach makes an important contribution towards a better understanding of what combination of landscape and invader properties can facilitate or prevent invasive spread in natural ecosystems. This should allow ecologists to more effectively predict and manage biological invasions.

Perturbation responses in co‐evolved model meta‐communities

“…Relative extinction event sizes are moderately positively correlated with the invader bodysize, as this property predicts the number of patches invaded (the strongest correlation is unsurprisingly between this outcome and the resulting extinctions). Increased invasion success for large‐bodied species with greater dispersal rates has been observed in other meta‐community invasion models (Häussler et al, 2021 ), and this does not seem dependent on the prior range of the species. In §3.2, we did not find an initial correlation between bodysize and range (Table 3 ), although as large species maintain smaller populations they may have especially benefited from re‐introductions with uniform populations.…”

“…Increased invasion success for large-bodied species with greater dispersal rates has been observed in other meta-community invasion models (Häussler et al, 2021), and this does not seem dependent on the prior range of the species. In §3.2, we did not find an initial correlation between bodysize and range (Table 3), although as large species maintain smaller populations they may have especially benefited from re-introductions with uniform populations.…”

“…Dispersal and meta‐community dynamics alone are sufficient to account for complex food web networks (Pillai et al, 2011 ). The topology of the spatial network mediates the relative roles of mass effects and species sorting in spatial pattern formation (Suzuki & Economo, 2021 ), and the successfulness and impact of species invasions (Häussler et al, 2021 ) to govern the structure of linked communities (Gross et al, 2020 ). In particular, functionally large distances separating species in space facilitates co‐existence for less‐competitive generalists and thus enables greater biodiversity (Barter & Gross, 2017 ).…”

Heterogeneity in the isolation of patches may be essential for the action of metacommunity mechanisms

“…The metacommunity theory mostly stands on the analyses of spatially implicit systems, in which all patches are equally connected to all others (but see Economo and Keitt, 2010;Ai et al, 2013;Suzuki and Economo, 2021), and species have equal dispersal rates (Borthagaray et al, 2015a,b;Grainger and Gilbert, 2016). Furthermore, spatially explicit models and experiments usually focus on the idealized spatial arrangement of local communitiesrandom locations, chains, stars, and grids (Economo andKeitt, 2008, 2010;Borthagaray et al, 2014;Arim et al, 2016;Grainger and Gilbert, 2016;Häussler et al, 2021;Suzuki and Economo, 2021). Therefore, it is assumed that dispersal gradients equally affect all species and communities (Grainger and Gilbert, 2016;Suzuki and Economo, 2021).…”

Metacommunity robustness to invasion in mutualistic and antagonistic networks

“…As we know, natural communities are complex assemblages of species (or functional groups) which interact through a variety of trophic and non-trophic processes, for example, antagonistic and mutualistic networks (Cronin and Haynes, 2004;Baiser et al, 2010). Thus, whether and how the architecture of interaction networks can influence community invasibility has recently become a hot topic in invasion ecology, and significant progress has been made in our understanding of the architecture-invasibility relationship (Aizen et al, 2008;Hui et al, 2016;Valdovinos et al, 2018;Frost et al, 2019;Hui and Richardson, 2019;Häussler et al, 2021).…”