Bryophyte-Feeders in a Basal Brachyceran Lineage (Diptera: Rhagionidae: Spaniinae): Adult Oviposition Behavior and Changes in the Larval Mouthpart Morphology Accompanied with the Diet Shifts

Abstract

Dipteran larval morphology exhibits overwhelming variety, affected by their diverse feeding habits and habitat use. In particular, larval mouthpart morphology is associated with feeding behavior, providing key taxonomic traits. Despite most larval Brachycera being carnivorous, a basal brachyceran family, Rhagionidae, contains bryophyte-feeding taxa with multiple feeding habits. To elucidate the life history, biology, and morphological evolution of the bryophyte-feeding rhagionids, the larval feeding behavior and morphology, and the adult oviposition behavior of four species belonging to three genera of Spaniinae (Spania Meigen, Litoleptis Chillcott and Ptiolina Zetterstedt) are described. Moreover, changes of the larval morphology associated with the evolution of bryophyte-feeding are traced by molecular phylogenetic analyses. Spania and Litoleptis (thallus-miners of thallose liverworts) share a toothed form of apical mandibular sclerite with an orifice on its dorsal surface, which contrasts to those of the other members of Rhagionidae possessing a blade-like mandibular hook with an adoral groove; whereas, Ptiolina (stem borer of mosses) exhibits a weak groove on the adoral surface of mandible and highly sclerotized maxilla with toothed projections. Based on the larval feeding behavior of the thallus-miners, it is inferred that the toothed mandibles with the dorsal orifice facilitate scraping plant tissue and then imbibing it with a great deal of the sap. A phylogeny indicated that the bryophyte-feeding genera formed a clade with Spaniopsis and was sister to Symphoromyia, which presumably are detritivores. This study indicates that the loss or reduction of adoral mandibular groove and mandibular brush is coincident with the evolution of bryophyte-feeding, and it is subsequently followed by the occurrence of dorsal mandibular orifice and the loss of creeping welts accompanying the evolution of thallus-mining.

First Tropical American Species of the “Relict” GenusLitoleptis,and Relationships in Spaniinae (Diptera: Rhagionidae)

“…Larval lifespan is approximately 11 months, with adults emerging in early spring (generally April). As expected, larval morphology of the bryophagous spaniines differs significantly from the typical, predatory morphology (Imada and Kato, 2016b fig. 5C).…”

First tropical American species of the "relict" genus Litoleptis, and relationships in Spaniinae (Diptera, Rhagionidae)

“…Larval lifespan is approximately 11 months, with adults emerging in early spring (generally April). As expected, larval morphology of the bryophagous spaniines differs significantly from the typical, predatory morphology (Imada and Kato, 2016b). Spania and Litoleptis (but not Ptiolina) lack creeping welts; the mandibles are reduced in size (not the typical bladelike hooks), with the preapical orifice shifted from the adoral surface to a dorsal position (the central canal is retained), and the mandibular brush is lost, including in Ptiolina.…”

“…My cladogram ( fig. 7) differs from Imada and Kato's (2016b) 28S rRNA phylogeny, with Spania + Litoleptis as sister groups, rather than Spaniopsis + Litoleptis. The most important point, though, is that in both schemes Litoleptis is a highly derived genus of Spaniinae, and according to Kerr's (2010) analysis, Spaniinae is a highly derived group within Rhagionidae (Stuckenberg [2001] notwithstanding).…”

“…Spania and Litoleptis (but not Ptiolina) lack creeping welts; the mandibles are reduced in size (not the typical bladelike hooks), with the preapical orifice shifted from the adoral surface to a dorsal position (the central canal is retained), and the mandibular brush is lost, including in Ptiolina. The labrum of the larva has biserial rows of coarse, retrorse teeth (Imada and Kato, 2016b).…”

Description and molecular characterization of Chrysopilus kafkai sp. nov. (Diptera: Rhagionidae) from Serra da Bodoquena (Mato Grosso do Sul, Brazil)

“…Adult rhagionids are medium to large-sized flies (4-20 mm), usually found in woodlands and rainforests (Kerr, 2010). The biology of the group is mostly unknown -the genus Symphoromyia Frauenfeld is reported as hematophagous, and a few other genera, such as Spania Meigen, Litoleptis Chilcott and Ptiolina Zetterstedt, have bryophyte-feeder larvae (Imada & Kato, 2016).…”