Hatching asynchrony affects intraspecific competition among larval mosquitoes

Abstract

Aedes eggs may hatch in synchrony, yielding individuals of similar age and size, or asynchrony, yielding individuals of different ages and sizes, depending on rainfall. Multiple freshwater species have similar variation in developmental synchrony of immatures. We tested alternative hypotheses that asynchronous hatch modifies intraspecific competition among Aedes aegypti (L.) (Diptera: Culicidae) compared with synchronous hatch via: (1) priority effects; or (2) reduced temporal overlap. We placed pairs of newly hatched larvae into water‐filled vials with food at either the same time (synchronous) or 4 days apart (asynchronous) and recorded survival, sex, development time and wing length for the resulting adults. For second‐eclosing adults, asynchronous hatch yielded larger adult females compared to synchronous hatch, but there were no effects on male sizes, nor on survival or development times. For first‐eclosing adults, asynchronous hatch yielded both larger sizes and shorter development times for both sexes compared with synchronous hatch. These results are consistent with the hypothesis that hatch asynchrony reduced the impact of intraspecific competition, possibly by reducing the time that larvae co‐occurred. We found limited evidence for priority effects, suggesting that the dominant effect of hatch asynchrony of 4 days is reduced intraspecific competition, probably via reduced temporal overlap. These results suggest that priority advantage is only one possible effect of asynchrony and that there may be benefits to developmental asynchrony under certain circumstances. Further experiments with different degrees of asynchrony, at different resource levels, would enhance our understanding of intraspecific competition among larval mosquitoes and likely other freshwater taxa with variable hatch asynchrony.