Molecular phylogenetics of the holly leaf miners (Diptera : Agromyzidae : Phytomyza): Species limits, speciation, and dietary specialization

A molecular phylogenetic analysis was conducted to determine relationships and to investigate character evolution in the Phytomyza ilicis group of lea fmining flies on hollies (Aquifoliaceae: Ilex). A total of 2207 bp of the m itochondrial cytochrome oxidase I and II genes were sequenced for all known holly leafminers, as well as for several undescribed members of this group . Maximum-parsimony analysis of the sequence data indicates that these leaf miners form a monophyletic group with the inclusion of an undescribed leafm iner that feeds on the distantly related plant Gelsemium sempevirens (Logan iaceae). Species boundaries of previously known and of undescribed holly le afmining species were confirmed with the molecular data, with one exception . Optimization of variable ecological and morphological characters onto the most parsimonious phylogeny suggests that these traits are evolutionarily labile, requiring multiple instances of convergence and/or reversal to expl ain their evolutionary history. Speciation in holly leafminers is associate d with host shifts and appears to involve colonization of new hosts more of ten than cospeciation as the hosts diverge. Monophagy is the most common fe eding pattern in holly leafminers, and more generalized feeding is inferred to have evolved at least two separate times, possibly as a prelude to spec iation. (C) 2000 Academic Press.