Precipitation and temperature effects on populations of Aedes albopictus (Diptera: Culicidae): implications for range expansion

Abstract

We investigated how temperature and precipitation regime encountered over the life cycle of Aedes albopictus (Skuse) affects populations. Caged populations of A. albopictus were maintained at 22, 26, and 30 degrees C. Cages were equipped with containers that served as sites for oviposition and larval development. All cages were assigned to one of three simulated precipitation regimes: (1) low fluctuation regime - water within the containers was allowed to evaporate to 90% of its maximum before being refilled, (2) high fluctuation regime - water was allowed to evaporate to 25% of its maximum before being refilled, and (3) drying regime - water was allowed to evaporate to complete container dryness before being refilled. Greater temperature and the absence of drying resulted in greater production of adults. Greater temperature in combination with drying were detrimental to adult production. These precipitation effects on adult production were absent at 22 degrees C. Greater temperatures and drying treatments yielded higher and lower eclosion rates, respectively and, both yielded greater mortality. Development time and size of adults decreased with increased temperatures, and drying produced larger adults. Greater temperatures resulted in greater egg mortality. These results suggest that populations occurring in warmer regions are likely to produce more adults as long as containers do not dry completely. Populations in cooler regions are likely to produce fewer adults with the variability of precipitation contributing less to variation in adult production. Predicted climate change in North America is likely to extend the northern distribution of A. albopictus and to limit further its establishment in arid regions.

Fig. 1

Least squares means ± SE mean number of adults produced During and at the End of the experiment. Dashed lines indicate bivariate means that are significantly different from one another by multivariate pairwise comparisons (Scheiner 1993).

Fig. 2

Least squares means ± SE mean eclosion and mortality of adults. Letters denote bivariate means that are significantly different from one another by multivariate pairwise comparisons (Scheiner 1993).

Fig. 3

Least squares means ± SE median days to development for the first cohort of males and females. Lower case and upper case letters denote significant differences based upon univariate pairwise comparisons among temperature treatments for males and females, respectively.

Fig. 4

Least squares means ± SE residual wing length (During) and mean wing length (End) for adult females. Dashed lines indicate residual wing lengths that are equivalent to the predicted value for the sample date. Letters denote significant differences among bivariate means.

Fig. 5

Least squares means ± SE mean interval of time (d) between water additions for containers in the lab experiment and mean time for tires to decrease to ≤90%, ≤25%, and dry for field sites 1 and 2. No estimate was calculable to 90% at site 2 because no tires had volumes >90%. Points lacking error bars indicate standard errors that were too small to appear on the graph.

Fig. 6

Proportions of tires at sites 1 and 2 that have tire water volumes ≥90%, ≥25%, and dry.

Fig. 7

Mean daily ambient air temperatures and weekly water temperatures for sites 1 and 2. Mean water temperatures for sites 1 and 2 were determined over the entire monitoring period. For sites 1 and 2, points lacking error bars indicate standard errors that were too small to appear on the graph.