Pan-American <i>Chironomus calligraphus</i> Goeldi, 1905 (Diptera, Chironomidae): Species or Complex? Evidence from External Morphology, Karyology and DNA Sequencing

Abstract

Abstract Chironomus (Chironomus) calligraphus Goeldi, 1905, previously known from the Neotropics, is newly identified as a member of midge communities across the southern U.S.A.. The karyotype is described for the first time, as is that of the related Chironomus spec. WOC, known only as larvae from the southeastern United States. Morphological descriptions for the adult male, pupa, and larva of C. calligraphus are emended, including characters distinguishing the species in the southern Nearctic. Intraspecific variation diminishes the diagnostic value of certain standard morphometrics. The first gene sequences for C. calligraphus are offered based on a fragment of mitochondrial cytochrome c oxidase subunit II. Patterns of variation are not congruent among data sets. Morphology and karyology show minor and clinal regional differences, whereas mtDNA sequences suggest the sympatric coexistence of two haplotype groups. However, taxonomic distinctions are considered unwarranted pending further evidence. C. calligraphus thrives in a range of conditions and habitats, including small and temporary waters. This ability is presumed to have facilitated the species' wide Pan-American distribution, but also its high potential as a nuisance to humans.