Data from: Female mosquitoes disperse further when develop under predation risk

Predation is one of the strongest selective forces in nature. Organisms characterized by a complex life cycle, undergoing an ontogenetic niche shift, can reduce predation risk on natal stages by metamorphosing earlier. Yet, this anti-predatory response may incur numerous life-history-related costs. Interestingly, the consequence of larval predation risk on adult dispersal, a key trait dictating the persistence of spatially-structured populations, is largely understudied. Here, we explored the effect of larval predation risk on the life-history and dispersal characteristics of female adults in the mosquito Culex pipiens. As predicted, mosquito larvae reared in the presence of a caged larvivorous-fish metamorphosed earlier, while also suffering from reduced survival. Despite this reduction in development time, the body size of emerging females was larger, implying that more resources were allocated to increase the growth rate, probably at the expense of reduced maintenance and storage. This shift in energy allocation translated into decreased pupa and adult survival. Remarkably, the respective dispersal distance of these larger bodied females was greater. We suggest that the increase in dispersal distance allows these females to cover larger areas, while searching for oviposition sites that are safer than their natal aquatic habitat. Exploring the effects of larval conditions on adult dispersal is central for understanding the distribution of organisms with a complex life cycle in spatially heterogeneous environments, and specifically for disease transmission by mosquitoes

Inter- and intra-specific density-dependent effects on life history and development strategies of larval mosquitoes.

We explored how inter- and intra-specific competition among larvae of two temporary-pool mosquito species, Culiseta longiareolata and Ochlerotatus caspius, affect larval developmental strategy and life history traits. Given that their larvae have similar feeding habits, we expected negative reciprocal inter-specific interactions. In a microcosm experiment, we found sex-specific responses of larval survival and development to both intra- and inter-specific larval competition. C. longiareolata was the superior competitor, reducing adult size and modifying larval developmental time of O. caspius. We observed two distinct waves of adult emergence in O. caspius, with clear sex-specific responses to its inter-specific competitor. In males, this pattern was not affected by C. longiareolata, but in females, the timing and average body size of the second wave strongly varied with C. longiareolata density. Specifically, in the absence of C. longiareolata, the second wave immediately followed the first wave. However, as C. longiareolata abundance increased, the second wave was progressively delayed and the resulting females tended to be larger. This study improves our understanding of the way intra- and inter-specific competition combine to influence the life histories of species making up temporary pond communities. It also provides strong evidence that not all individuals of a cohort employ the same strategies in response to competition

Species-specific non-physical interference competition among mosquito larvae.

Individuals of different sex, size or developmental stage can compete differently and hence contribute distinctively to population dynamics. In species with complex life cycles such as insects, competitive ability is often positively correlated with larval developmental stage. Yet, little is known on how the development and survival of early-instars is influenced by interference from late-instar larvae, especially at low densities when exploitative competition is expected to be negligible. Furthermore, the specificity and mechanisms by which interference competition operates are largely unknown. We performed two complementary experiments aiming to quantify the competitive effects of late instar Ochlerotatus caspius on early instar larvae at low densities and under high resource supply rate. The first experiment examined the net effect of interference by 4(th) on 1(st) instar O. caspius larvae, relative to the effect of 1(st) instars on themselves. The second experiment examined the effect of species-specific, non-physical interference competition (i.e., cage larvae) by 4(th) on 1(st) instar O. caspius larvae at low or high densities. Specifically, we compared the responses of O. caspius larvae raised in the presence of caged con- or hetero-specific, Culiseta longiareolata, with that of larvae in the empty-cage control group. As expected, interference from late instar larvae had a net negative effect on the development rate of first instars. In contrast, the presence of caged con-specifics (non-physical interference) accelerated the development rate of O. caspius, however, this pattern was only evident at the low density. Notably, no such pattern was detected in the presence of caged hetero-specifics. These results strongly suggest the existence of species-specific growth regulating semiochemicals

Adult size variables summarized by Principal Components Analysis (PCA).

<p>The first principal component (PC-1) of Principal Components Analysis (PCA) of the four body size variables (wing, femur, and tibia lengths and body mass) transformed to their Log₁₀ values. The table details the eigenvalues of the covariance matrix, percent variance explained by the vectors and the factor coordinates of the variables, based on correlations (factor loadings).</p

The effect of Treatment (Homogeneous vs. Heterogeneous stage), on the wing length of males emerging from the experimental cups.

<p>Nested ANOVA testing for the effect of treatment on male wing length. Individuals are nested within experimental cups, i.e., experimental cups rather than individuals are considered as the replicates. Practically, in the statistical model, experimental cup ID was nested within treatment. Note that the MS of this nested variable was used as the error term of treatment.</p