Scale dependent effects of native prey diversity, prey biomass and natural disturbance on the invasion success of an exotic predator

Abstract

There is growing support for the general notion that the drivers of invasion success often shift from biotic to abiotic factors with increasing spatial scale. Most of this research, however, has been conducted on a single trophic level; i.e. it has primarily looked at how the diversity of native competitors may influence invasion success. Less attention has been paid to understanding how native prey diversity may influence the invasion success of exotic predators and whether such biotic factors are scale-dependent. We used a hierarchical spatial survey of 17 stream communities to test whether native prey diversity, along with native prey biomass, algal resource abundance and annual stream discharge, influenced the abundance of an exotic crayfish predator, and whether the importance of these factors were scale-dependent. We used a hierarchical generalized linear model to evaluate the influence of these community and stream characteristics on exotic crayfish abundance at both the transect scale (1 m 2 ) and the stream scale (400 m 2 ). Our results indicated that at the stream scale, high stream discharge significantly limited invader abundance. However, at the smaller transect scale, native prey biomass was a significant driver of invasion success and positively correlated with invader abundance. We suggest that our results add to the emerging pattern that abiotic processes are stronger determinants of invasion success at large spatial scales, whereas biotic processes become more important with decreasing spatial scale. However, for predator invasions, prey biomass, not prey diversity may be a more important for driver of invasion success at small spatial scales.

The signal crayfish is not a single species: cryptic diversity and invasions in the Pacific Northwest range of Pacifastacus leniusculus

“…The broad extent of our phylogeographic sampling in the Pacific Northwest and archiving of genetic data should allow other researchers to identify native range sources for P. leniusculus populations in their regions (e.g. Our narrowing of the probable native range for P. leniusculus also means that models predicting the global invasive distribution for this crayfish are likely to underestimate the extent of climatic niche shifts the species has actually experienced , while our suggestion that invasive populations of P. leniusculus originate from large, low-altitude rivers of the lower Columbia River catchment may explain the observed intolerance of these crayfish for steep stream gradients and high water velocity (Light, 2003;Pintor & Sih, 2011). Our narrowing of the probable native range for P. leniusculus also means that models predicting the global invasive distribution for this crayfish are likely to underestimate the extent of climatic niche shifts the species has actually experienced , while our suggestion that invasive populations of P. leniusculus originate from large, low-altitude rivers of the lower Columbia River catchment may explain the observed intolerance of these crayfish for steep stream gradients and high water velocity (Light, 2003;Pintor & Sih, 2011).…”

“…Although observed occasionally to tolerate estuarine conditions (Miller, 1960), we do not anticipate that P. leniusculus can disperse long distances through salt water. Finally, steep stream gradients and high water velocity severely limit the dispersal and distribution of invasive P. leniusculus populations elsewhere (Light, 2003;Pintor & Sih, 2011), potentially precluding natural colonisation above hydraulic barriers like the fast-flowing Fraser River canyon (McPhail & Lindsey, 1986). Finally, steep stream gradients and high water velocity severely limit the dispersal and distribution of invasive P. leniusculus populations elsewhere (Light, 2003;Pintor & Sih, 2011), potentially precluding natural colonisation above hydraulic barriers like the fast-flowing Fraser River canyon (McPhail & Lindsey, 1986).…”

Aquatic invasive species: challenges for the future

“…In contrast, experiments conducted at fine spatial scales showed an opposite pattern, with a negative association between growth rates of invasive species and native diversity (Xu et al, 2004;Michelan et al, 2013). Because different factors likely influence invasions at different spatial scales, aquatic ecologists should carry out more studies that encompass different scales simultaneously (e.g., see Pintor & Sih, 2011).…”

Reduced vertebrate diversity independent of spatial scale following feral swine invasions

“…The lack of scale-dependent effects of feral swine on species richness we observed here brings into question whether the scaledependence hypothesis is a universal consequence of biological invasions. In fact, we were unable to find any examples of vertebrate invasions having scale-dependent effects on native species richness even though this relationship commonly has been demonstrated when the invader is a plant (e.g., Fridley, Brown, & Bruno, 2004, Davies et al, 2005, Powell et al, 2013 or invertebrate (e.g., Mayer, Keats, Rudstam, & Mills, 2002, Altieri et al, 2010, Pintor & Sih, 2011. Those scale-dependent effects were likely a function of facilitation (Rodriguez, 2006 Baruzzi & Krofel, 2017).…”