Abstract
The wheat midge, Sitodiplosis mosellana, is an important pest in Northern China. We tested the hypothesis that the population structure of this species arises during a range expansion over the past 30 years. This study used microsatellite and mitochondrial loci to conduct population genetic analysis of S. mosellana across its distribution range in China. We found strong genetic structure among the 16 studied populations, including two genetically distinct groups (the eastern and western groups), broadly consistent with the geography and habitat fragmentation. These results underline the importance of natural barriers in impeding dispersal and gene flow of S. mosellana populations. Low to moderate genetic diversity among the populations and moderate genetic differentiation (F ST = 0.117) between the two groups were also found. The populations in the western group had lower genetic diversity, higher genetic differentiation and lower gene flow (F ST = 0.116, Nm = 1.89) than those in the eastern group (F ST = 0.049, Nm = 4.91). Genetic distance between populations was positively and significantly correlated with geographic distance (r = 0.56, P<0.001). The population history of this species provided no evidence for population expansion or bottlenecks in any of these populations. Our data suggest that the distribution of genetic diversity, genetic differentiation and population structure of S. mosellana have resulted from a historical event, reflecting its adaptation to diverse habitats and forming two different gene pools. These results may be the outcome of a combination of restricted gene flow due to geographical and environmental factors, population history, random processes of genetic drift and individual dispersal patterns. Given the current risk status of this species in China, this study can offer useful information for forecasting outbreaks and designing effective pest management programs.
Highlights
The wheat midge (Gehin) Sitodiplosis mosellana (Diptera: Cecidomyiidae) is one of the most destructive pests of wheat, and is distributed in most wheat-producing regions of the world, including Europe, Asia, and North America [1,2,3]
Significant differences in geographical and environmental factors between the two regions have led to great differences in genetic diversity, genetic differentiation and population structure of S. mosellana, which has been demonstrated at several scales
The results of this study indicate that S. mosellana populations exhibit significant genetic differentiation, with FST values ranging from low to high among these populations
Summary
The wheat midge (Gehin) Sitodiplosis mosellana (Diptera: Cecidomyiidae) is one of the most destructive pests of wheat, and is distributed in most wheat-producing regions of the world, including Europe, Asia, and North America [1,2,3]. S. mosellana was first detected in China in the early 1310s. This species has one generation per year. The larvae hatch after 4–7 days, crawl into the floret and feed on the surface of developing wheat kernels for 2–3 weeks. Once moist conditions are detected, the mature larvae drop to the ground, burrow into the soil and overwinter as diapausing cocooned larvae. Wheat midge infestation can result in kernels shriveling, cracking and deformity, and reduce crop yields and lower the grade of harvested grain [5]. In China, wheat midge outbreaks have occurred many times in the past 60 years, causing economic damage to wheat yields, especially in northern China [3]
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