Mitochondrial and nuclear diversity in the green oak leaf roller Tortrix viridana L. (Lepidoptera, Tortricidae) from Sardinia

摘要

The Green oak leaf roller Tortrix viridana is one of the most harmful pest of the Palearctic oaks. The young larvae of T. viridana develop inside the flushing buds and their egg hatch is synchronized with the bud burst of the oaks. The aim of the study was to investigate the genetic structure and variation of mitochondrial and nuclear loci in Sardinian populations associated with deciduous (Quercus pubescens) and evergreen (Q. suber and Q. ilex) oaks. We performed multilocus analyses (COI, COII mitochondrial genes and eight microsatellites) in about two hundreds individuals collected on all the three oak species coming from the most important forest districts in Sardinia Island, Italy. The populations were also characterized by egg hatching, after comparison in semi-field tests for egg development. Eighty-five mitochondrial haplotypes were found, with three ones shared among all populations, except the most southern one. A high haplotype diversity (H =0.90) and a low nucleotide diversity (? =0.003) have been observed. Microsatellites were highly variable with alleles ranging from 4 to 56 for locus and polymorfic information content values varying from 0.510 to 0.945. AMOVA tests were performed by structuring samples in different groups (geographic districts/oak species/egg development). The highest values of Fixation indexes resulted grouping populations according to early or late egg hatching. Furthermore, we tested for sex-biased dispersal, estimating pairwise FST, FIS, and relatedness r at nuclear loci separately for the sexes. We produced evidence for non random patterns of gene flow probably mediated by male biased dispersal, with values significantly higher in females than in males and females the phylopatric sex. In support of a male biased dispersal, nuclear and mitochondrial markers provided different results in the matter of genetic structure, with mitochondrial loci, unlike microsatellites, highlighting significant differentiation levels among populations.