Habitat complexity and sex-dependent predation of mosquito larvae in containers

Abstract

Studies in aquatic systems have shown that habitat complexity may provide refuge or reduce the number of encounters prey have with actively searching predators. For ambush predators, habitat complexity may enhance or have no effect on predation rates because it conceals predators, reduces prey detection by predators, or visually impairs both predators and prey. We investigated the effects of habitat complexity and predation by the ambush predators Toxorhynchites rutilus and Corethrella appendiculata on their mosquito prey Aedes albopictus and Ochlerotatus triseriatus in container analogs of treeholes. As in other ambush predator-prey systems, habitat complexity did not alter the effects of T. rutilus or C. appendiculata whose presence decreased prey survivorship, shortened development time, and increased adult size compared to treatments where predators were absent. Faster growth and larger size were due to predator-mediated release from competition among surviving prey. Male and female prey survivorship were similar in the absence of predators, however when predators were present, survivorship of both prey species was skewed in favor of males. We conclude that habitat complexity is relatively unimportant in shaping predator-prey interactions in this treehole community, where predation risk differs between prey sexes.

Fig. 1

Tri-variate LS means (from MANOVA) for effects of T. rutilus predators and habitat complexity on a male and b female A. albopictus survivorship to adulthood, development time to adulthood, and adult mass

Fig. 2

Tri-variate LS means (from MANOVA) for effects of T. rutilus predators on male and female A. albopictus survivorship to adulthood, development time to adulthood, and adult mass

Fig. 3

Bi-variate LS means (± SE) for habitat complexity effect on male and female A. albopictus survivorship to adulthood and development time to adulthood. Numbers above LS means show habitat complexity treatment (e.g., number of whole cloth maple leaves added). Lower and upper case letters indicate significant differences for males and females, respectively [experiment wise α = 0.05, sequential Bonferroni method (Rice 1989)]. LS means for mass were omitted since they contributed little to the overall habitat structure effect

Fig. 4

LS means (± SE) for significant treatment effects of T. rutilus predators in five habitat structures (0, 4, 10, 14, and 20 artificial leaves added) on A. albopictus λ′ (lambda). Letters indicate significant differences among λ′ values for the significant treatment interaction [Tukey–Kramer adjustment for multiple comparisons (SAS Institute 1989)]

Fig. 5

Tri-variate LS means (from MANOVA) for the effects of C. appendiculata predators on male and female A. albopictus survivorship to adulthood, development time to adulthood, and adult mass

Fig. 6

Tri-variate LS means (from MANOVA) for the effects of C. appendiculata predators on male and female O. triseriatus survivorship to adulthood, development time to adulthood, and adult mass