Geographic Variation in the Expression of Autogeny in Aedes togoi (Diptera: Culicidae) Under Different Temperature and Photoperiod Conditions

Abstract

Larval developmental time, adult size, and the expression of autogeny were studied in eight populations of Aedes togoi (Theobald) originating from 4.8 degrees N to 49.2 degrees N under four experimental conditions of temperature and photoperiod (20 degrees C and 10:14 [L:D] h; 20, 25, 30 degrees C and 16:8 [L:D] h). Larval developmental time and adult scutum length decreased as a function of increasing rearing temperature. In northern populations at 20 degrees C, larval developmental time was shorter in short-day than in long-day conditions. Females of tropical and subarctic populations remained autogenous under different conditions and produced many autogenous eggs in the first batch. In subtropical and temperate populations, the percentage of autogenous females varied from 0 to 100%, being highest at low temperature and short-day condition. A correlation analysis of population traits indicated that the autogeny rate was correlated positively with larval developmental time and the number of eggs per autogenous female. The life-history traits did not show a simple clinal gradient over mean annual temperature of the locality of origin, except that adult scutum length decreased with an increase in mean temperature. A principal components analysis for female life-history traits revealed a continuous latitudinal change from temperate to tropical populations; populations at low latitudes were small in adult size and more autogenous. Subarctic populations showed a departure from this trend, having large adult size but high autogeny rate.