Comparison of the thermal performance between a population of the olive fruit fly and its co-adapted parasitoids

Abstract

Long-term separation of a host from its native parasitoids may result in divergent thermal adaptation between host and parasitoid. The olive fruit fly, Bactrocera oleae (Rossi), most likely originated from Sub-Saharan Africa, but has since had a long invasion history in cultivated olives that spans geographical barriers and continents. This study compared three major thermal performance profiles (development, survival, and reproduction) across a wide range of temperatures (10–34°C) among a Californian population of the olive fruit fly and two African parasitoids, Psyttalia lounsburyi (Silvestri) and Psyttalia humilis (Silvestri), believed to have co-adapted with the fruit fly in its native range. Temperature ranges for the development and survival were 10–30°C for the fly, 10–28°C for P. lounsburyi, and 14–32°C for P. humilis. There was no difference in any thermal performance measured between two P. humilis populations (Kenya and Namibia) tested. The most suitable temperature ranges for reproduction were 22–30°C for the fly, 18–32°C for P. humilis, and 18–26°C for P. lounsburyi. The results showed slight differences in the thermal profiles among olive fruit fly and both parasitoids species, with P. humilis being more heat tolerant whereas P. lounsburyi was less heat tolerant than the fruit fly. The results are discussed with respect to thermal co-adaptation and classical biological control of the olive fruit fly.