Adaptive photoperiodic egg diapause is retained in Florida populations of invasive Aedes albopictus

More than 20 years have passed since A. albopictus, descendents of invasive colonizers from temperate Japan, became established in northern Florida and spread rapidly southward to become the State’s most common day-biting mosquito. Adults of this species may be active in south Florida in every month, but many eggs laid in December and January of 2006-07 in West Palm Beach County did not respond to a standard hatching stimulus. Females from geographic populations, collected in 2008 from north and south Florida, exposed to short (10L:14D) daylengths at 21 degrees C laid eggs of regionally variable diapause incidence. Short days induced strong diapause responses in north Florida populations (Pensacola and Jacksonville). Some subtropical populations (e.g., Vero Beach) showed decreased diapause compared to ten years previously (vide: Lounibos et al. [2003] Ann. Entomol. Soc. Am. 96:512), while others had unexpectedly high current incidence (e.g., Card Sound), suggesting possible recolonization from more northern localities. Eggs derived from short-day Vero Beach females survived January exposures in the field significantly better than eggs laid by long day controls, substantiating the adaptive nature of the polymorphic diapause response.