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

Johanna Häussler,Ulrich Brose,Remo Ryser

doi:10.1111/oik.07503

Johanna Häussler, Ulrich Brose + Show 1 more

Open Access

https://doi.org/10.1111/oik.07503

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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.

Highlights

The number of invasive species increases without any sign of saturation (Seebens et al 2017), raising concern for biodiversity loss and biotic homogenization (Courchamp et al 2017, Ricciardi et al 2017)
Simulating biological invasions in meta-foodwebs in landscapes that differ in their spatial configuration of habitat and nutrient supply shows that both landscape properties affect invasion success
We found that invader biomass density relative to the total biomass density in the landscape decreased with nutrient supply (Fig. 2d) – the total biomass density in the landscape was increasing with nutrient supply (Fig. 2c)

Summary

Introduction

The number of invasive species increases without any sign of saturation (Seebens et al 2017), raising concern for biodiversity loss and biotic homogenization (Courchamp et al 2017, Ricciardi et al 2017). The ‘invasibility’ of a native community should increase with unexploited niche space and high nutrient and prey availability (Shea and Chesson 2002, Pantel et al 2017, Frost et al 2019) but decrease with the number of predators an invasive species has in the invaded community (enemy release hypothesis; Mitchell and Power 2003). Lurgi et al (2014) could show that in their simulation study larger and more generalist species were the most successful invaders These examples highlight that species-level network properties, such as trophic position and diet breadth, together with network complexity can play a key role for invasion success (Romanuk et al 2009, Lurgi et al 2014, Frost et al 2019)

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