Low-temperature threshold for egg survival of a post-diapause and non-diapause European aedine strain,Aedes albopictus (Diptera: Culicidae)

Background: the interplay between global warming and invasive arthropods in temperate zones is of utmost interest in terms of the potential expansions of vector-borne diseases. up to now,investigations on the recent establishment of mosquito vectors have focused on temperatures during their phases of activity. however,cold temperatures may also act as a strong ecological constraint. projected changes in winter climate indicate an increase of mean minimum temperatures of the coldest quarter,less frequent days with frost and a shorter frost-season in europe at the end of the century. nevertheless,single cold extremes are also expected to persist under warming scenarios,which have a strong impact on reproduction success. methods: here,the temperature constraints of european aedes albopictus eggs,which had passed through a diapause,compared to non-diapausing eggs were examined systematically under controlled laboratory conditions. additionally,one tropical strain of ae. albopictus and of ae. aegypti was used in the comparison. results: the lower temperature threshold tolerated by the european eggs of ae. albopictus which have undergone a diapause,was -10°c for long term exposures (12 and 24h) and -12°c for 1h exposure. non-diapausing eggs of european ae. albopictus were found to hatch after a -7°c cold treatment (8,12 and 24h exposure). both tropical aedine species only tolerated the long term treatment at -2°c. neither ae. albopictus nor ae. aegypti eggs hatched after being exposed to -15°c. survival was mainly influenced by temperature (f = 329.2,df = 1,p < 0.001),whereas the duration of the cold treatment only significantly influenced the hatching response at the thermal limits of survival (f = 5.6,df = 1,p = 0.031) but not at 0°c (f = 0.1,df = 1,p = 0.730). hatching success after the cold treatment was significantly increased in european eggs,which have undergone a diapause compared to non-diapausing eggs (f = 14.7,df = 3,p < 0.001). these results illustrate rapid adaptation. conclusions: here,low temperature thresholds for aedine mosquito egg survival were detected. the compilation of risk maps for temperate regions can substantially be improved by considering areas where an establishment of a vector population is unlikely due to winter conditions. © 2012 thomas et al.; licensee biomed central ltd.