Assessing effects of non‐native crayfish on mosquito survival

Abstract

Introductions of nonnative predators often reduce biodiversity and affect natural predator-prey relationships and may increase the abundance of potential disease vectors (e.g., mosquitoes) indirectly through competition or predation cascades. The Santa Monica Mountains (California, U.S.A.), situated in a global biodiversity hotspot, is an area of conservation concern due to climate change, urbanization, and the introduction of nonnative species. We examined the effect of nonnative crayfish (Procambarus clarkii) on an existing native predator, dragonfly nymphs (Aeshna sp.), and their mosquito larvae (Anopheles sp.) prey. We used laboratory experiments to compare the predation efficiency of both predators, separately and together, and field data on counts of dragonfly nymphs and mosquito larvae sampled from 13 local streams. We predicted a lower predation efficiency of crayfish compared with native dragonfly nymphs and a reduced predation efficiency of dragonfly nymphs in the presence of crayfish. Dragonfly nymphs were an order of magnitude more efficient predators than crayfish, and dragonfly nymph predation efficiency was reduced in the presence of crayfish. Field count data showed that populations of dragonfly nymphs and mosquito larvae were strongly correlated with crayfish presence in streams, such that sites with crayfish tended to have fewer dragonfly nymphs and more mosquito larvae. Under natural conditions, it is likely that crayfish reduce the abundance of dragonfly nymphs and their predation efficiency and thereby, directly and indirectly, lead to higher mosquito populations and a loss of ecosystem services related to disease vector control.

Damselfly eggs alter their development rate in the presence of an invasive alien cue but not a native predator cue

“…The presence of chemical signals (cues) coming from a predator, called kairomones, in the environment can trigger a variety of prey responses. For example, kairomones directly affect prey feeding behavior (Naddafi et al., 2007), the predation efficiency of prey (Bucciarelli et al., 2018), passive defense traits (Czarnoleski et al., 2011), metabolic rate (Antoł et al., 2018), and life‐history traits (Czarnołęski et al., 2006; Sniegula, Nsanzimana, et al., 2019; Sniegula et al., 2020). However, we still do not have enough information on the effects of predator cues on prey traits during the initial developmental stage, that is, the egg stage (but see Ireland et al., 2007; Li & Jackson, 2005; Miner et al., 2010; Sniegula, Nsanzimana, et al., 2019; Sniegula et al., 2020), and we do not know whether the naïve prey hypothesis holds for the egg stage.…”

Modelling the damage costs of invasive alien species

“…By reducing or extirpating native populations (Bellard et al 2016;Vanbergen et al 2018), IAS considerably affect biotic and abiotic interactions of recipient communities, with frequent top-down or bottom-up cascading effects (Walsh et al 2016;Bucciarelli et al 2018). As such, IAS can compromise ecosystem structure, function and service provisioning (Malcolm and Markham 2000;Stigall 2010;Vanbergen et al 2018;Blackburn et al 2019).…”

Modelling the damage costs of invasive alien species

“…By reducing or extirpating native populations (Bellard et al 2016, Vanbergen et al 2018), IAS considerably affect biotic and abiotic interactions of recipient communities, with frequent top-down or bottom-up cascading effects (Walsh et al 2016, Bucciarelli et al 2018).…”