Abstract
BackgroundInvasive pest species have large impacts on agricultural crop yields, and understanding their population dynamics is important for ensuring food security. The oriental fruit moth Grapholita molesta is a cosmopolitan pest of stone and pome fruit species including peach and apple, and historical records indicate that it has invaded North and South America, Europe, Australia and Africa from its putative native range in Asia over the past century.ResultsWe used 13 microsatellite loci, including nine newly developed markers, to characterize global population structure of G. molesta. Approximately 15 individuals from each of 26 globally distributed populations were genotyped. A weak but significant global pattern of isolation-by-distance was found, and G. molesta populations were geographically structured on a continental scale. Evidence does not support that G. molesta was introduced to North America from Japan as previously proposed. However, G. molesta was probably introduced from North America to The Azores, South Africa, and Brazil, and from East Asia to Australia. Shared ancestry was inferred between populations from Western Europe and from Brazil, although it remains unresolved whether an introduction occurred from Europe to Brazil, or vice versa. Both genetic diversity and levels of inbreeding were surprisingly high across the range of G. molesta and were not higher or lower overall in introduced areas compared to native areas. There is little evidence for multiple introductions to each continent (except in the case of South America), or for admixture between populations from different origins.ConclusionsCross-continental introductions of G. molesta appear to be infrequent, which is surprising given its rapid worldwide expansion over the past century. We suggest that area-wide spread via transport of fruits and other plant materials is a major mechanism of ongoing invasion, and management efforts should therefore target local and regional farming communities and distribution networks.
Highlights
Invasive pest species have large impacts on agricultural crop yields, and understanding their population dynamics is important for ensuring food security
We suggest that area-wide spread via transport of fruits and other plant materials is a major mechanism of ongoing invasion, and management efforts should target local and regional farming communities and distribution networks
Null allele frequencies varied from 0.05 to 0.33 among the 13 microsatellite loci (Table 2), which is typical for lepidopteran DNA loci [38], and lower than or comparable to other studies that have used microsatellite markers to determine the genetic structure of populations [39,40]
Summary
Invasive pest species have large impacts on agricultural crop yields, and understanding their population dynamics is important for ensuring food security. The oriental fruit moth Grapholita molesta is a cosmopolitan pest of stone and pome fruit species including peach and apple, and historical records indicate that it has invaded North and South America, Europe, Australia and Africa from its putative native range in Asia over the past century. Global interest in the ecology of agricultural systems has driven a substantial amount of fundamental research into plant-herbivore interactions, modes of plant (i.e. weed) and invertebrate dispersal and adaptation, and the role of multi-trophic interactions in community dynamics [1]. A growing need to understand the potential effects of climate change on cash crop production systems [2], combined with the necessity of increasing worldwide crop yields in response to projected global population growth [3], continue to motivate research into fundamental and applied questions in ecology and evolutionary biology. Assumed to be native to China [7], G. molesta is distributed throughout temperate regions of Asia, Europe, The Americas, Africa, and Australia
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