Intraguild Predation and Cannibalism among Larvae of Detritivorous Caddisflies in Subalpine Wetlands

Abstract

Comparative data from subalpine wetlands in Colorado indicate that larvae of the limnephilid caddisfl.ies, Asynarchus nigriculus and Limnephilus externus, are reciprocally abundant among habitats-Limnephilus larvae dominate in permanent waters, whereas Asynarchus larvae dominate in temporary basins. The purpose of this paper is to report on field and laboratory experiments that link this pattern of abundance to biotic interactions among larvae. In the first field experiment, growth and survival were compared in single and mixed species treatments in littoral enclosures. Larvae, which eat mainly vascular plant detritus, grew at similar rates among treatments in both temporary and permanent habitats suggesting that exploitative competition is not important under natural food levels and caddis fly densities. However, the survival of Limnephilus larvae was reduced in the presence of Asynarchus larvae. Subsequent behavioral studies in laboratory arenas revealed that Asynarchus larvae are extremely aggressive predators on Limnephilus larvae. In a second field experiment we manipulated the relative sizes of larvae and found that Limnephilus larvae were preyed on only when Asynarchus larvae had the same size advantage observed in natural populations. Our data suggest that the dominance of Asynarchus larvae in temporary habitats is due to asymmetric intraguild predation (IGP) facilitated by a phenological head start in development. These data do not explain the dominance of Limnephilus larvae in permanent basins, which we show elsewhere to be an indirect effect of salamander predation.Behavioral observations also revealed that Asynarchus larvae are cannibalistic. In contrast to the IGP on Limnephilus larvae, Asynarchus cannibalism occurs among same-sized larvae and often involves the mobbing of one victim by several conspecifics. In a third field experiment, we found that Asynarchus cannibalism was not density-dependent and occurred even at low larval densities. We hypothesize that Asynarchus IGP and cannibalism provide a dietary supplement to detritus that may be necessary for the timely completion of development in these nutrient-poor, high-elevation wetlands.

Nutrient enrichment differentially affects body sizes of primary consumers and predators in a detritus‐based stream

“…For instance, some large-bodied detritivores, which primarily consume detritus at early instars, switch to cannibalism and intraguild predation during later instars (Wissinger et al 1996). Therefore, one could interpret the positive responses of large primary consumers (i.e., later instars) in the treatment stream to ontogenetic omnivory and consumption of small-bodied primary consumers.…”

A growth/mortality trade-off in larval salamanders and the coexistence of intraguild predators and prey

“…Several previous studies have also shown that, among taxonomically similar species, intraguild predators have higher absolute growth rates than their intraguild prey when raised separately under the same conditions (Hurd 1988;Griffiths et al 1994;Wissinger et al 1996;Suhling 2001). Further, growth advantages for intraguild predators are likely to be established or exacerbated when guild members interact, since intraguild predators can both consume intraguild prey and cause them to modify their behavior or habitat use (Polis and Holt 1992).…”

Larval cannibalism, time constraints, and adult fitness in caddisflies that inhabit temporary wetlands

“…It is especially conspicuous among the mainly detritivorous larvae of the caddisfly Asynarchus nigriculus Banks (Limnephilidae; Wissinger et al 1996). Cannibalism in Asynarchus differs from that observed in most populations because it is a result of mobbing behavior among same-sized larvae in synchronously developing cohorts (Wissinger et al 2003).…”