Population Genetic Differentiation And Spatiotemporal Patterns Of Plutella Xylostella And Cotesia Vestalis(Cotesia Plutellae)

According to the host-tracking hypothesis,parasitoids are likely to show concordant or delayed spatiotemporal patterns of hosts.The diamondback moth,Plutella xylostella,is the most notorious insect pest of cruciferous plants.Cotesia vestalis(Cotesia plutellae)is one of the most important biological control agents of Plutella xylostella.Here,we compared the phylogeographic structures of P.xylostella and Cotesia vestalis using both nuclear genes(EF1? and 28S(or CAD))and mitochondrial genes(cox1,cytb and nad1).P.xylostella showed high haplotype diversity and low nucleotide diversity,and C.vestalis presented moderate haplotype diversity and low nucleotide diversity.The pairwise FST analysis showed lower level of differentiation among the P.xylostella populations than among the C.vestalis populations.Using Mantel tests,we obtained r=0.340(P=0.001)of P.xylostella,and r=-0.033(P=0.829)of C.vestalis based on combined mitochondrial genes and nuclear genes,indicating that there was no correlation between genetic and geographical distances among the studied populations of C.vestalis,and little correlation among P.xylostella populations.Based on nuclear genes or mitochondrial genes,haplotype network analysis revealed monsoon group was oldest,and two species were composed of two or more population aggregates;Demographic history analysis indicated that recent demographic expansion occurred in P.xylostella with unimodal mismatch distributions,but not in C.vestalis.Compared phylogeographies between mitochondria and nuclear,we found that mitochondria phylogeographies did not have infected and uninfected clades,indicating that mitochondria phylogenetic patterns were no influenced by Wolbachia infections.In conclusion,our results demonstrated that spatiotemporal patterns of C.vestalis was lagging behind P.xylostell,which suggested that C.vestalis may have migrated along with P.xylostella.Our research provides a example of using phylogeographic approaches to resolve the correlation between P.xylostella and parasitoids,and important genetic information for better management of P.xylostella by C.vestalis.