Genetic structure of the cypress seed chalcid Megastigmus wachtli (Torymidae) within its Mediterranean distribution.
Polymorphic microsatellites were used to assess the genetic structure of populations of Megastigmus wachtli. Populations associated with evergreen cypress (Cupressus sempervirens) in its native range were compared with those in areas where the cypress had been introduced. Cones were collected in late spring at 10 locations in Europe. The average observed heterozygosity across populations ranged from 32.2 to 58.7%, with a mean of 43.6% over all loci. Italian and French populations had the lowest mean heterozygote proportions and low mean allele numbers. Observed values for pairwise gene flow estimates indicated strong levels of differentiation for most populations, except some which are geographically close. Neighbour-joining trees showed 2 distinct clusters. One group included the western populations of M. wachtli (Tunisia, France and Italy), while the 2nd group included Moroccan and east Mediterranean populations.