Asymmetric Evolution of Photoperiodic Diapause in Temperate and Tropical Invasive Populations of <I>Aedes albopictus</I> (Diptera: Culicidae)

Abstract

Aedes albopictus became established in Brazil and the USA during the same approximate period of the mid-1980s and spread rapidly in both countries in succeeding years. Early populations in the USA, believed derived from temperate Japan, all possessed a photoperiodically inducible egg diapause, but a population from Brazil, of probable tropical origins, did not. Based on responses of geographic populations to a common short (10L:14D) day length, we demonstrate that the spread of A. albopictus in Florida from more temperate USA has been associated with a gradual loss of diapause, such that diapause incidence is now positively correlated with latitude in the southern USA. In Brazil, most populations tested 15 yr after the initial invasion show no evidence of diapause, except for three from the two southernmost states (>26°S), in which a small, but significant percentage of eggs from mothers exposed to short day lengths were dormant. Diapause reduction in the southern USA and diapause acquisition by A. albopictus in southern Brazil have not resulted in similar response levels at comparable latitudes in the two countries, in part because of genetic constraints of different founder populations from temperate and tropical origins and different selective regimes in the two invaded countries.