The Systematics and Phylogeny of the Stenochironomus Complex (Xestochironomus, Harrisius, and Stenochironomus) (Diptera:Chironomidae)

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Language: English with bilingual abstract in English and French

The Stenochironomus complex contains all those species which exhibit the highly modified, mining larval form previously recognized as typical of only the genus Stenochironomus Kieffer: larvae with a dorsoventrally compressed head capsule, expanded thoracic segments and a long, flaccid abdomen. The complex includes members of Xestochironomus Sublette & Wirth (New World), Harrisius Freeman (Australian Region), Stenochironomus (cosmopolitan) and two larval forms. one from New Zealand and the other from Africa.

This revision provides analysis of 12 species of Xestochironomus (five new). four species of Harrisius, and 54 species of Neotropical and Holarctic Stenochironomus (32 new named species. two new species not named. and four new combinations: S. innocuus (Williston). S. semifumosus (Edwards). S. longilobatus (Tokunaga) and S. gracilivalva (Kieffer)). Of these species, the pupae and fourth instar larvae are described for two species of Xestochironomus, Harrisius pallidus Freeman and 24 of the named species of Stenochironomus. Descriptions, diagnoses, keys, and distribution maps are provided for all species in each available stage. Stenochironomus taeniapennis (Coquillett, 1901), S. zonopterus (Mitchell, 1908), and S. exquisitus (Mitchell, 1908) are newly recognized as junior synonyms of S. hilaris (Walker, 1848).

A cladistic analysis of all these species suggests that the Stenochironomus complex is monophyletic. The African larval form is the sister group of all other members; Xestochironomus is the sister group of Harrisius, the New Zealand larval form and Stenochironomus; and Stenochironomus is the sister group of Harrisius plus the New Zealand larval form. These relationships suggest possible southem continental affinities. Stenochironomus is composed of two monophyletic species groups, the subgenus Stenochironomus s. str. with species whose larvae mine wood and the new subgenus Petalopholeus (type-species. S. cinctus Townes) with species whose larvae mine leaves.

Cladistic pattems show that Caribbean species are related to other New World species, and that North American species are related to Neotropical or Palaearctic species. Larval food type and ecological differences are analyzed using cladistic relationships. The plesiotypic habitat for species of the Stenochironomus complex is running waters. The phylogenetic relationships of Stenochironomus species and their mite parasites are compared and show little congruence.

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