Chill coma recovery of Ceratitis capitata adults across the Northern Hemisphere

The Mediterranean fruit fly, Ceratitis capitata (Diptera: Tephritidae), is an invasive pest, that is currently expanding its geographic distribution from the Mediterranean coasts to more temperate areas of Europe. Given that low temperature is a primary determinant of insect species' range boundaries especially in the Northern Hemisphere with pronounced seasonality, we used chill coma recovery time for assessing latitudinal clines in basal chill tolerance of C. capitata adults. We selected six populations obtained from areas with broad climatic variability based on the main bioclimatic variables of temperature and precipitation, spanning a latitudinal range of about 19 degrees from Middle East to Central Europe. Adults were exposed to 0 degrees C for 4 h, and time to regain the typical standing position of a fly at 25 degrees C were recorded. The post-stress survival after a period of 8 days was also recorded. Results revealed that adults from Israel and Austria were less chill tolerant than those from Greece, resulting in curvilinear trends with latitude. Analysis of macroclimatic conditions revealed combined effects of latitude (as a proxy of photoperiod) and macroclimatic conditions on chill coma recovery time. Nonetheless, there was not a deleterious effect on post-recovery survival, except for flies obtained from the northern most point (Vienna, Austria). Overall, it seems that evolutionary patterns of basal chill coma recovery time of C. capitata adults are driven mainly by local climatic variability.

Automated summary

The study investigated the basal chill tolerance of the Mediterranean fruit fly across different latitudes and found that the climatic variability, particularly in terms of temperature and precipitation, has an impact on the fly's cold tolerance. The results revealed latitudinal trends in chill coma recovery time and indicated the combined effects of latitude and macroclimatic conditions. Overall, the study suggests that local climatic variability drives the evolutionary patterns of basal chill tolerance in the fruit fly.