Contributions of temporal segregation, oviposition choice, and non-additive effects of competitors to invasion success of Aedes japonicus (Diptera: Culicidae) in North America

Abstract

The mosquito Aedes japonicus (Diptera: Culicidae) has spread rapidly through North America since its introduction in the 1990s. The mechanisms underlying its establishment in container communities occupied by competitors Aedes triseriatus and Aedes albopictus are unclear. Possibilities include (A) temporal separation of A. japonicus from other Aedes, (B) oviposition avoidance by A. japonicus of sites containing heterospecific Aedes larvae, and (C) non-additive competitive effects in assemblages of multiple Aedes. Containers sampled throughout the summer in an oak-hickory forest near Eureka, MO showed peak abundance for A. japonicus occurring significantly earlier in the season than either of the other Aedes species. Despite this, A. japonicus co-occurred with one other Aedes species in 53 % of samples when present, and co-occurred with both other Aedes in 18 % of samples. In a field oviposition experiment, A. japonicus laid significantly more eggs in forest edge containers than in forest interior containers, but did not avoid containers with low or high densities of larvae of A. triseriatus, A. albopictus, or both, compared to containers without larvae. Interspecific competitive effects (measured as decrease in the index of performance, λ') of A. triseriatus or A. albopictus alone on A. japonicus larvae were not evident at the densities used, but the effect of both Aedes combined was significantly negative and super-additive of effects of individual interspecific competitors. Thus, neither oviposition avoidance of competitors nor non-additive competitive effects contribute to the invasion success of A. japonicus in North America. Distinct seasonal phenology may reduce competitive interactions with resident Aedes.

Keywords: Container community; Multispecies competition; Oviposition behavior; Seasonal phenology.

Fig. 1

Results of survival analysis of the 2009 colonization study. a Cumulative proportion of containers that have been initially colonized by each Aedes species by each sample week. Both A. japonicus and A. triseriatus colonization curves differed significantly from A. albopictus, but did not differ from each other. b Cumulative proportion of containers that have attained peak abundance of each species by each sample week. All species peak abundance curves significantly differed from one another

Fig. 2

Mean (±SE) abundance of larvae of each Aedes species per liter of sample during the 2009 colonization study

Fig. 3

Mean (±SE) number of A. japonicus larvae hatched and reared from eggs collected from the 2008 oviposition study for combinations of container treatment and locations (forest edge vs. interior). a Containers collected July 24. b Containers collected September 13

Fig. 4

Mean proportion survival of females (+SE) in response to inter- and intraspecific larval densities in multispecies competition experiment, for a A. japonicus, b A. triseriatus, c A. albopictus. Treatment abbreviations correspond to abbreviations given in Table 1. Letters indicate means that do not significantly differ from each other. For each species, filled points represent actual mean survivorship (±SE, =√MSE/n). The open point represents expected survivorship in the multispecies treatments if effects of competing species on target species survivorship were additive and accurately predicted by effects on the target species observed in the 2-species combinations

Fig. 5

Mean finite rate of increase in response to inter- and intraspecific larval densities in multispecies competition experiment, for a A. japonicus, b A. triseriatus, c A. albopictus. Treatment abbreviations correspond to abbreviations given in Table 1. For each species, filled points represent actual mean λ′ (±SE, =√MSE/n); the open point represents expected λ′ in the multispecies treatment if effects of competing species on target species λ′ were additive and accurately predicted by effects on the target species observed in the 2-species combinations. Asterisk a mean for A. japonicus significantly different from means from all other treatments for A. japonicus