Exploration for olive fruit fly parasitoids across Africa reveals regional distributions and dominance of closely associated parasitoids

Xingeng Wang,Robert K Straser,Alan A Kirk,Charles H Pickett,Arnaud Blanchet,Kent M Daane,Kim A Hoelmer,Vaughn M Walton

doi:10.1038/s41598-021-85253-y

Abstract

The olive fruit fly, Bactrocera oleae, has been a key pest of olives in Europe and North America. We conducted the largest exploration for parasitoids associated with the fly across Sub-Saharan Africa (Kenya, Namibia, and South Africa) including some of the fly’s adjoining regions (Canary Islands, Morocco, Réunion Island and Tunisia). From Sub-Saharan regions, four braconids were collected: Bracon celer, Psytallia humilis, P. lounsburyi, and Utetes africanus. Results showed that their regional dominance was related to climate niches, with P. humilis dominant in hot semi-arid areas of Namibia, P. lounsburyi dominant in more tropical areas of Kenya, and U. africanus prevalent in Mediterranean climates of South Africa. Psytallia concolor was found in the Canary Islands, Morocco and Tunisian, and the Afrotropical braconid Diachasmimorpha sp. near fullawayi on Réunion Island. Furthermore, we monitored the seasonal dynamics of the fly and parasitoids in Cape Province of South Africa. Results showed that fruit maturity, seasonal variations in climates and interspecific interactions shape the local parasitoid diversity that contribute to the low fly populations. The results are discussed with regard to ecological adaptations of closely associated parasitoids, and how their adaptations impact biocontrol.

Highlights

Psytallia concolor was the only species found in the Canary Islands, Tunisia and Morocco, whereas D. sp. near fullawayi was the only species recovered in the Réunion Island (Fig. 1)
The other four species were found in Namibia and South Africa and three of them were found in Kenya, with P. lounsburyi, P. humilis and U. africanus being the predominant parasitoid species in Kenya, Namibia and South Africa, respectively (Fig. 1)
The sub-Saharan regions of Namibia, South Africa and Kenya maintained the highest diversity of braconid B. oleae parasitoid species, supporting the argument of a Sub-Saharan origin of B. oleae[22,23,24]

Summary

Introduction

Economic returns on successful programs are overwhelmingly positive[6], but CBC programs require proper steps to be successfully implemented to minimize the number of natural enemy releases that are inconsequential or have negative non-target impacts on recipient e cosystems[7,8]. For herbivorous invaders, this requires a fundamental understanding of the natural enemy impact in its native range, biology and host specificity, as well as potential tri-trophic interactions that develop from a high degree of co-adaptation between plant—phytophagous pest—entomophagous arthropods and the impact of habitat and environment on the selected natural e nemy[7].

Methods

Results

Conclusion