Terellia Species in Lebanon: Ovipositor Morphology and DNA Barcoding

Abstract

Terellia is a genus of nonfrugivorous tephritid fly that widespread in the palearctic region. In Lebanon, six species have been recorded to exploit various thistle hosts at different elevations: Terellia colon, T. fuscicornis, T. luteola, T. gynaecochroma, T. quadratula, T. serratulae. Terellia females use their ovipositor to lay eggs in the flower heads of thistles as the larvae feed on the seeds. The aculeus or ovipositor tip of tephritid females is usually adapted to the host exploited and it is equipped with sensory receptors to guide the female in the egg-laying process. Terellia species in Lebanon differ in their host range. Terellia serratulae behaves as a generalist while the other species are restricted to one or few plant host species. Previous work showed that T. serratulae appears to consist of distinct host races, but further investigation has been needed to determine the extent of intraspecific variation and gene flow between T. serratulae associated with different plant hosts. The relationship between different Terellia species and different host associations has not been examined. This study aimed to elucidate the relationship between the various Terellia species in Lebanon and to determine the extent of intraspecific variations among generalist and specialist species with the premise that the mitochondrial gene COX1 and the ovipositor structure and size are effective tools for the identification and differentiation of Terellia species and their host-associated populations. Significant differences between Terellia species were found with respect to the ovipositor length, position of the sensilla (lateroventral grooves), and the width of the aculeus tip. Variations in the fine structures of ovipositor were detected and distinguishing characters were identified for different Terellia species and host races. Sensilla on the dorsal side of the ovipositor are reported for the first time. Consensus sequences for each Terellia species in Lebanon have been generated. Phylogenetic analysis using COX1 show that the four studied Terellia species in Lebanon fall into two clades. Terellia luteola which had a distinctive ovipositor, is the sole member of one major clade. In the other major clade, T. gynaecochorma, with its characteristic aculeus tip, falls into a separate subclade. Terellia serratulae falls into different, host-associated subclades, and host race formation of T. serratulae associated with Picnomon acarna is confirmed.