Genetic variability in Italian populations of Drosophila suzukii

Gabriella Tait,Fabiana Sassù,Antonio Biondi,Alessandro Cini,Lorenzo Tonina,Lino Ometto,Nuray Baser,Giorgia Sollai,Gloria Antonini,Gianfranco Anfora,Silvia Vezzulli

doi:10.1186/s12863-017-0558-7

Abstract

BackgroundDrosophila suzukii is a highly destructive pest species, causing substantial economic losses in soft fruit production. To better understand migration patterns, gene flow and adaptation in invaded regions, we studied the genetic structure of D. suzukii collected across Italy, where it was first observed in 2008. In particular, we analysed 15 previously characterised Simple Sequence Repeat (SSR) markers to estimate genetic differentiation across the genome of 278 flies collected from nine populations.ResultsThe nine populations showed high allelic diversity, mainly due to very high heterozygosity. The high Polymorphism Information Content (PIC) index values (ranging from 0.68 to 0.84) indicated good discrimination power for the markers. Negative fixation index (FIS) values in seven of the populations indicated a low level of inbreeding, as suggested by the high number of alleles. STRUCTURE, Principal Coordinate and Neighbour Joining analysis also revealed that the Sicilian population was fairly divergent compared to other Italian populations. Moreover, migration was present across all populations, with the exception of the Sicilian one, confirming its isolation relative to the mainland.ConclusionsThis is the first study characterising the genetic structure of the invasive species D. suzukii in Italy. Our analysis showed extensive genetic homogeneity among D. suzukii collected in Italy. The relatively isolated Sicilian population suggests a largely human-mediated migration pattern, while the warm climate in this region allows the production of soft fruit, and the associated D. suzukii reproductive season occurring much earlier than on the rest of the peninsula.

Highlights

Drosophila suzukii is a highly destructive pest species, causing substantial economic losses in soft fruit production
The spotted wing drosophila (SWD), Drosophila suzukii Matsumura (Diptera: Drosophilidae), is a pest species which has spread from its original range in Asia to a number of western countries in the past decade, including the Mediterranean basin [1], Europe, and USA [1,2,3]
The history of the geographical spread and infestation of D. suzukii is still under investigation: it is known that in 1939 this species was first recorded in Japan (Kanzawa 1939), while in the 1980s it was collected on the island of Hawaii [4]

Summary

Introduction

Drosophila suzukii is a highly destructive pest species, causing substantial economic losses in soft fruit production. Single Nucleotide Polymorphism (SNP) and Simple Sequence Repeat (SSR) markers have played an increasingly significant role in the study of genetic differentiation across species populations [15]. Thanks to their great discrimination power and high reproducibility and variability, SSRs represent one of the most robust and informative molecular markers available for genotyping individuals [16]. Their use in Drosophila species was pivotal in studying intrapopulation genetic variation and evolution [14, 17,18,19,20]

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Conclusion