GENETIC DIFFERENTIATION IN ZEIRAPHERA-DINIANA (LEPIDOPTERA, TORTRICIDAE, THE LARCH BUDMOTH) - POLYMORPHISM, HOST RACES OR SIBLING SPECIES

Eleven larch- and pine-feeding populations of the larch budmoth were studied in Western Europe using 24 allozyme loci. Hierarchical F-statistics between larch and pine forms (F(ST)approximate to 0.065) were much greater than those between localities within larch (F(ST)approximate to 0.002) and within pine (F(ST)approximate to 0.026), even when sympatric host-associated populations were considered. Analysis of Nei's genetic distance produced similar results, and a UPGMA tree of all populations consistently clustered samples from the same hosts together. Three loci, autosomal Pgm and Mdh-s and sex-linked Idh-s, were the most important loci involved in differences between the two forms. Previously considered to be conspecific, it is now clear that the larch and pine biotypes of Z. diniana are either host races (sensu Diehl & Bush, 1984) or good sympatric species which hybridize rarely. Regardless of taxonomic status, the distribution of larch and pine in the Pleistocene, phenological differences between the two hosts, together with the great vagility of Z. diniana, an outbreak pest, suggest that sympatric or parapatric differentiation is at least as likely as allopatric divergence.