Abstract
The oriental fruit moth Grapholita ( = Cydia) molesta is a key fruit pest globally. Despite its economic importance, little is known about its population genetics in its putative native range that includes China. We used five polymorphic microsatellite loci and two mitochondrial gene sequences to characterize the population genetic diversity and genetic structure of G. molesta from nine sublocations in three regions of a major fruit growing area of China. Larval samples were collected throughout the season from peach, and in late season, after host switch by the moth to pome fruit, also from apple and pear. We found high numbers of microsatellite alleles and mitochondrial DNA haplotypes in all regions, together with a high number of private alleles and of haplotypes at all sublocations, providing strong evidence that the sampled area belongs to the origin of this species. Samples collected from peach at all sublocations were geographically structured, and a significant albeit weak pattern of isolation-by-distance was found among populations, likely reflecting the low flight capacity of this moth. Interestingly, populations sampled from apple and pear in the late season showed a structure differing from that of populations sampled from peach throughout the season, indicating a selective host switch of a certain part of the population only. The recently detected various olfactory genotypes in G. molesta may underly this selective host switch. These genetic data yield, for the first time, an understanding of population dynamics of G. molesta in its native range, and of a selective host switch from peach to pome fruit, which may have a broad applicability to other global fruit production areas for designing suitable pest management strategies.
Highlights
In insect field populations, genetic diversity and genetic structure can be affected by various factors, such as range of origin as opposed to invaded regions, geographical distance and host plant species [1,2,3]
Its putative native range includes China, where it is thought to have co-evolved with its primary host peach [9,10], but little is known yet about its population genetics in this area
Our objective was to investigate the genetic diversity of G. molesta in its putative range of origin and its genetic structure in a key fruit growing area of China, as well as the consequence of seasonal dynamics with host switch from primary to secondary hosts
Summary
Genetic diversity and genetic structure can be affected by various factors, such as range of origin as opposed to invaded regions, geographical distance and host plant species [1,2,3]. Some studies have documented that genetic diversity and structure are associated with the dispersal ability of the insect concerned [4,5,6] Populations in their native range show a high genetic diversity, whilst populations in invaded regions usually show reduced genetic diversity [7,8]. Its putative native range includes China, where it is thought to have co-evolved with its primary host peach [9,10], but little is known yet about its population genetics in this area This moth completes three to seven generations per year depending on latitude and elevation [11,12]. Despite the importance of the seasonal dynamics given by this host switch, consequences on patterns of population structure in the oriental fruit moth are yet unknown
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