Abstract
Genetic comparisons of parasitoids and their hosts are expected to reflect ecological and evolutionary processes that influence the interactions between species. The parasitoid wasp, Cotesia vestalis, and its host diamondback moth (DBM), Plutella xylostella, provide opportunities to test whether the specialist natural enemy migrates seasonally with its host or occurs as resident population. We genotyped 17 microsatellite loci and two mitochondrial genes for 158 female adults of C. vestalis collected from 12 geographical populations, as well as nine microsatellite loci for 127 DBM larvae from six separate sites. The samplings covered both the likely source (southern) and immigrant (northern) areas of DBM from China. Populations of C. vestalis fell into three groups, pointing to isolation in northwestern and southwestern China and strong genetic differentiation of these populations from others in central and eastern China. In contrast, DBM showed much weaker genetic differentiation and high rates of gene flow. TESS analysis identified the immigrant populations of DBM as showing admixture in northern China. Genetic disconnect between C. vestalis and its host suggests that the parasitoid did not migrate yearly with its host but likely consisted of resident populations in places where its host could not survive in winter.
Highlights
Parasitism is one of the most important biological interactions that shapes biodiversity and influences community processes (Hudson, Dobson, & Lafferty, 2006; Wood et al, 2007)
Lack of genetic structure in populations collected from Taiwan island indicated that the C. vestalis showed dispersal ability in local area, as reported in many other parasitoids (Couchoux et al, 2016; Nair et al, 2016; Nyabuga et al, 2011)
We have demonstrated that the parasitoid and its host show contrasting patterns of genetic differentiation
Summary
Parasitism is one of the most important biological interactions that shapes biodiversity and influences community processes (Hudson, Dobson, & Lafferty, 2006; Wood et al, 2007). C. vestalis can attack and develop in other lepidopteran species in the laboratory (Cameron, Walker, Keller, & Clearwater, 1997), it is generally regarded as a specialist parasitoid of DBM (Arvanitakis, David, & Bordat, 2014) This parasitoid appears to be as widespread as DBM and occurs in its migratory range (Furlong et al, 2013; Grzywacz et al, 2010). It is possible that high levels of gene flow are present in this species, given that populations of C. vestalis in temperate regions are thought to include migratory individuals as well as those emerging from diapause (Furlong et al, 2013). The results of our study will help to illustrate the processes that influence the interactions between a specialist parasitoid and its migratory host and guide the conservation and utilization of C. vestalis for pest control, more generally
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