Abstract
Predators may affect prey population growth and community diversity through density mediated lethal and trait mediated non-lethal effects that influence phenotypic traits of prey. We tested experimentally the roles of thinning the density of prey (lethality) in the absence of predator cues and density and trait mediated effects (lethality + intimidation) of predatory midge Corethrella appendiculata on competing native and invasive mosquito prey. Predator-mediated reductions in prey and density reductions in the absence of C. appendiculata resulted in lower percent survivorship to adulthood and estimates of the finite rate of increase (λ′) for invasive mosquito Aedes albopictus relative to that of controls. In most instances, thinning the density of prey in the absence, but not in the presence, of C. appendiculata cues resulted in lower survivorship to adulthood and λ′ for native mosquito Aedes triseriatus relative to that of controls. Together, these results suggested trait mediated effects of C. appendiculata specific to each species of mosquito prey. Release from intraspecific competition attributable to density reductions in the absence, but not in the presence, of C. appendiculata enhanced growth and lengthened adult lifespan relative to that of controls for A. albopictus but not A. triseriatus. These results show the importance of predator-mediated density and trait mediated effects on phenotypic traits and populations of invasive and native mosquitoes. Species-specific differences in the phenotypic responses of prey may be due, in part, to longer evolutionary history of C. appendiculata with A. triseriatus than A. albopictus.
Highlights
Predators can have a major influence on prey population growth and community diversity [1,2,3]
Previous studies have demonstrated that interspecific interactions between A. triseriatus and A. albopictus may be altered by the presence of C. appendiculata
In the presence of C. appendiculata, the competitive advantage that A. albopictus has over A. triseriatus is diminished [43,45,46]
Summary
Predators can have a major influence on prey population growth and community diversity [1,2,3]. The presence of predators may have non-lethal (trait mediated) effects attributable to intimidation that alter phenotypic traits of prey [10,11,12] and even extend to non-prey populations [13]. Non-lethal effects of predators may include inducing changes in behavior, development, growth, morphology and physiology [10,14,15]. Predator cues induce development of defensive spines in Daphnia [16], alterations in shell morphology in snails [18], heavier exoskeletons and longer caudal filaments in mayflies [19], longer caudal spines in dragonflies [20], and reduced activity and use of refugia in amphibians, insects, and other animals [14,21]. A meta-analysis showed that the relative magnitude of non-lethal effects of predation may exceed those effects attributable to lethality [17]. Identification of non-lethal effects of predators (and measurement of their relative magnitude) is often difficult, especially when their effect is directionally similar to lethal effects of predators
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