Molecular phylogeny and systematics of leaf‐mining flies (Diptera: Agromyzidae): delimitation of Phytomyza Fallén sensu lato and included species groups, with new insights on morphological and host‐use evolution

Abstract

Phytomyza Falle´n is the largest genus of leaf-mining flies (Agromyzidae), with over 530 described species. Species of the superficially similar genus Chromatomyia Hardy have been included in Phytomyza by some authors and the status of the genus remains uncertain. Using 3076 bp of DNA sequence from three genes [cytochrome oxidase I (COI), CAD (rudimentary), phosphogluconate dehydrogenase (PGD)] and 113 exemplar species, we identified and tested the monophyly of host-associated species groups in Phytomyza and Chromatomyia and investigated the phylogenetic relationships among these groups. Chromatomyia is polyphyletic and nested largely within Phytomyza; two small groups of species, however, are related more closely to Ptochomyza and Napomyza.

Repeated climate-linked host shifts have promoted diversification in a temperate clade of leaf-mining flies

“…Phytomyza, with Ͼ700 described species (15), includes approximately a quarter of total diversity in the family Agromyzidae, larvae of which form characteristic mines ( Fig. 1) in leaves or other tissues of many different plant families (16,17).…”

“…It has long been considered to consist in major part of distinct species groups, each containing species that are morphologically homogeneous and feeding primarily on plants in the same family or order (16). Our recent molecular-phylogenetic study (15) sampled 108 Phytomyza species, representing nearly all species groups, for 3,076 bp of sequence from one mitochondrial and two nuclear gene regions. The resulting tree strongly corroborated the general validity of the species group concept, while clarifying the composition of and relationships among species groups.…”

“…Phytomyza species, each typically restricted to one or a few closely related species of herbs, feed mostly on plant families that are diverse and abundant in temperate regions (15,16). The main hosts fall into two disparate groups: Ranunculaceae, belonging to the oldest clade of eudicots (ranunculids); and asterids, especially Asteraceae, Apiaceae, Lamiaceae, Orobanchaceae, and Plantaginaceae, the last three belonging to the order Lamiales (21).…”

“…We initially hypothesized that shifts from Ranunculaceae to asterid hosts were contemporaneous with the earliest diversification of north temperate asterid lineages. Codiversification in this sense now seems very unlikely, as the earliest lineages of Phytomyza proved not to feed on Ranunculaceae (15), and many asterid herb lineages probably date to the early Cenozoic or earlier (24). Nonetheless, Ranunculaceae feeding does appear to have evolved early in the history of the genus, and given rise repeatedly to asterid feeding.…”

“…1) in leaves or other tissues of many different plant families (16,17). The genus is chiefly north temperate, with Ͼ90% of species occurring only in the Nearctic or Palearctic bioregions (15). It has long been considered to consist in major part of distinct species groups, each containing species that are morphologically homogeneous and feeding primarily on plants in the same family or order (16).…”