A new species of the Simulium (Simulium) striatum species-group (Diptera: Simuliidae) from Thailand: Description and phylogenetic relationship with its Thai members

Abstract

Simulium (Simulium) thilorsuense sp. nov. is described from females, males, pupae and mature larvae in Thailand. It is placed to the S. striatum species-group, and is distinguished from all the seven species of this species-group recorded from Thailand in the male by the greater number of male upper-eye (large) facets in 20 vertical columns and 19 or 20 horizontal rows, and in the pupa by the combination of the arrangement (2+3+3+2 from dorsal to ventral) and subequal thickness of gill filaments, and tubercles on the frons without secondary projection. It is similar in the female, male and pupa to S. (S.) pingtungense Huang & Takaoka from Taiwan but is distinguished in the larva by the presence of paired protuberances on abdominal segments 1–8 (absence in the latter species). It is similar to S. (S.) grisescens Brunetti from India, S. (S.) perakense Takaoka &Ya'cob from Peninsular Malaysia, and S. (S.) taythienense Takaoka, Sofian-Azirun & Ya'cob from Vietnam by sharing many characteristics including the haired basal portion of the female radius, dark legs of both female and male, male scutum with brassy short hairs, pupal gill with 10 filaments of the almost same thickness, arranged as 2+3+3+2 from dorsal to ventral, and larval abdomen with paired dorsal protuberances, but is distinguished from these three species by the greater number of male upper-eye (large) facets. Our genetic analysis using the fast-evolving nuclear big zinc finger (BZF) gene sequences revealed that this new species has an intraspecific variation ranging from 0.00% to 1.38%, and is separated from six Thai known species of the S. striatum species-group with an interspecific variation of 2.00–4.56%.