Age grading and gene flow of overwintered Bactrocera scutellata populations

Abstract

The striped fruit fly, Bactrocera scutellata, belongs to family Tephritidae. It infests pumpkin flowers. It is known to overwinter as adult stage with possible diapause development. However, its overwintering biology remains unclear. The objective of this study was to determine its overwintering regions in Korea. First, overwintering adults were collected and used to measure supercooling point (SCP) to understand its low limit temperature for survival. Male adults exhibited mean SCP at −7.2°C. During winter, Jeju and some southern mainland regions with temperatures above −7°C might be overwintering regions for B. scutellata. Based on such putative overwintering zone, male adult monitoring was performed from January to June in five different localities. Jeju and southern mainland regions (Yangsan, Uiryeong) had overwintered populations whereas mid- and northern regions (Andong, Guri) did not have such overwintered population. Amounts of pterin amounts in heads of overwintered populations were most increased in May and June, suggesting adult development and relatively long lifespan. Males collected in late spring possessed melanized testis filled with apparently matured spermatozoa. Genetic distances between overwintered populations of Jeju and mainland regions were measured using random amplification of polymorphic DNA. They showed separate clustering between Jeju and mainland populations. These results indicate that B. scutellata overwinters in both Jeju and southern mainland regions of Korea.