Symmerus
Walker, 1848
Species Guides
2Symmerus is a Holarctic of fungus gnats in the Ditomyiidae (Diptera). The genus comprises approximately 16 described distributed across the northern hemisphere, with records from Europe, North America, and Asia. A systematic revision recognized two subgenera: Symmerus s. str. and Psilosymmerus, the latter established with S. coqulus as type species. The genus has been subject to phylogenetic analysis using Hennig's phylogenetic , with transantarctic relationships documented in the related genus Australosymmerus.
Pronunciation
How to pronounce Symmerus: /ˈsɪmərəs/
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Identification
Members of Symmerus can be distinguished from related fungus gnats by characters of the wing venation and genitalia. The is separated from Australosymmerus by Holarctic versus transantarctic distribution and corresponding morphological differences. Subgenus Psilosymmerus is distinguished from Symmerus s. str. based on type characteristics of S. coqulus. Specific identification to species level requires examination of male genitalia and other subtle morphological features; S. lautus and S. annulatus are among the more frequently recorded European species.
Distribution
Holarctic distribution, recorded from Europe (including Denmark, Norway, Sweden), eastern North America, and Asia (Nepal). The is absent from the southern hemisphere, where the related genus Australosymmerus occurs.
Similar Taxa
- AustralosymmerusSister distinguished by transantarctic distribution (South America, Australia, New Zealand) versus Holarctic distribution of Symmerus; separated by morphological characters and phylogenetic analysis
More Details
Subgeneric classification
Two subgenera recognized: Symmerus s. str. and Psilosymmerus (type-: Symmerus coqulus Garrett). The latter subgenus was newly described in Munroe's 1974 systematic revision.
Phylogenetic significance
The phylogenetic reconstruction of Symmerus and Australosymmerus was used to infer that the ancestor lived in the northern hemisphere, with one phyletic line dispersing to the southern hemisphere and reaching South America by at least the early Tertiary.
Taxonomic note
placement has varied: treated as Mycetophilidae: Ditomyiinae in older literature, currently accepted in Ditomyiidae. S. tristis (Loew) and S. dilutus Fisher are synonyms of S. lautus (Loew).