High resources and infectious disease facilitate invasion by a freshwater crustacean

Abstract

It is well-established that both resources and infectious disease can influence species invasions, but little is known regarding interactive effects of these two factors. We performed a series of experiments to understand how resources and parasites can jointly affect the ability of a freshwater invasive zooplankton to establish in a population of a native zooplankton. In a life history trial, we found that both species increased offspring production to the same degree as algal resources increased, suggesting that changes in resources would have similar effects on both species. In a microcosm experiment simulating an invasion, we found that the invasive species reached its highest densities when there was a combination of both high resources and the presence of a shared parasite, but not for each of these conditions alone (i.e., a significant resource x parasite interaction). This result can be explained by changes in native host population density; high resource levels initially led to an increase in the density of the native host, which caused larger epidemics when the parasite was present. This high infection prevalence caused a subsequent reduction in native host density, increasing available resources and allowing the invasive species to establish relatively dense populations. Thus, in this system, native communities with a combination of high resource levels and parasitism may be the most vulnerable to invasions. More generally, our results suggest that parasitism and resource availability can have interactive, non-additive effects on the outcome of invasions.

Epidemics in native species influence the outcome of a species invasion

“…Both the native and invasive species can be reared in asexual isofemale lines and can be infected by M. bicuspidata as a result of incidental ingestion. Infection causes reduced feeding rates and mortality (Ebert 2000, Searle 2016,2018. Infected Daphnia release spores of the parasite into the environment upon death (Ebert et al 2000).…”

“…Additionally, when native and invasive species share parasites, the less susceptible host species can experience a competitive advantage in the presence of the parasite, facilitating or inhibiting the invasion (Price et al 1988 Infectious disease can also in uence invasions via changes to native host density. For example, an epidemic in native species can reduce native abundance and result in an increase in available resources, making it easier for the invasive species to establish (Prenter et al 2004;Havel et al 2015;Searle et al 2018). However, the size of an epidemic can affect how the native species density changes (Hudson and Dobson 1989;Hall et al 2011; Searle et al 2018) and this can potentially alter the resources available for the invasive species.…”

“…For example, an epidemic in native species can reduce native abundance and result in an increase in available resources, making it easier for the invasive species to establish (Prenter et al 2004;Havel et al 2015;Searle et al 2018). However, the size of an epidemic can affect how the native species density changes (Hudson and Dobson 1989;Hall et al 2011; Searle et al 2018) and this can potentially alter the resources available for the invasive species. For example, if large epidemics in native species result in very low native population abundance, then large epidemics may lead to high invasion success (Settle and Wilson 1990;Tuttle et al 2017).…”

Combined effects of salinity and infectious disease on Daphnia dentifera at multiple scales

“…We predicted that when individuals were exposed to a standard parasite dose (experiment 1), infection prevalence would not be affected by increased salinity because both the host and the parasite would be experiencing physiological stress, reducing both host resistance and parasite infectivity (Canhoto, Simões, Lúcia Gonҫalves, Guilhermino, & Bärlocher, 2017;Liu & Steiner, 2017). Additionally, because increasing salinity can decrease the population density of D. dentifera and transmission of the parasite is affected by host density (Searle, Hochstedler, Merrick, Ilmain, & Wigren, 2018;Searle, Cortez, et al, 2016), we predicted that increased salinity would reduce parasite transmission and decrease infection prevalence at the population level (experiment 2).…”

Epidemics in native species influence the outcome of a species invasion

“…Additionally, when native and invasive species share parasites, the less susceptible host species can experience a competitive advantage in the presence of the parasite, facilitating or inhibiting the invasion (Price et al 1988 Infectious disease can also in uence invasions via changes to native host density. For example, an epidemic in native species can reduce native abundance and result in an increase in available resources, making it easier for the invasive species to establish (Prenter et al 2004;Havel et al 2015;Searle et al 2018). However, the size of an epidemic can affect how the native species density changes (Hudson and Dobson 1989;Hall et al 2011; Searle et al 2018) and this can potentially alter the resources available for the invasive species.…”