Abstract
BackgroundThe 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.MethodsHere, 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.ResultsThe 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.ConclusionsHere, 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.
Highlights
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
The interplay between invasive arthropods and global warming is of utmost interest in terms of potential expansions or shifts of vector-borne infectious diseases [1,2]
Minimum survival temperature The minimum survival temperature tolerated by the European eggs of Ae. albopictus after a diapause (Figure 1) was -10°C for long term exposures (12 and 24h), while they survived short term exposure (1h) at -12°C
Summary
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. The interplay between invasive arthropods and global warming is of utmost interest in terms of potential expansions or shifts of vector-borne infectious diseases [1,2]. Aedes albopictus (Diptera: Culicidae) is a prominent constraints and on the climate-driven population dynamics of this mosquito have focused on the role of temperature during the phase of larval and adult activity, but rarely during the total life cycle [15]. In the case of shifts of populations to higher latitudes, the minimum temperatures and the mean temperature of the coldest month or quarter have been discussed as a proxy for the ecological constraints of Ae. albopictus [18]. Desiccation resistance in eggs increases due to higher concentrations of hydrocarbons at the egg surface [21]
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