Polypedilum

Biogeography of Polypedilum

Polypedilum is a cosmopolitan genus occurring in all zoogeographical regions except Antarctica. However, the subgenera Uresipedilum and Pentapedilum are nearly absent from the Neotropical region, while Tripodura is the most common subgenus in the Afrotropical and Neotropical regions. The not fully revised subgenus Polypedilum s. str. appears to be evenly distributed in all regions.

In the subgenera Cerobregma and Tripodura there appear to be a vicariance pattern between Brazil and West Africa (Vårdal et al. 2001; Saether & Ekrem 2003). Judging on the preferred cladogram of Tripodura (Vårdal et al. 2001 fig. 6) there are multiple sister group relationships between Brazilian and West African species. The subgenus Cerobregma contains few species, most of them Afrotropical and East Asian, with the two apparently most plesiomorphic, basal species based on pupae, found in Brazil. For both subgenera eastern South America is the most likely area of origin. An origin in South America and a vicariance pattern with West Africa was postulated also by Adam and Saether (1999) for the genus Nilothauma Kieffer which perhaps is the only Chironomini genus sharing the triangular tergite VIII with Polypedilum. This pattern now has been confirmed by the description of several new Neotropical species with a revised phylogeny (Mendes 2007).

The northern warm-eurotherm Gondwanian or Inabrezian distribution discussed in Saether and Sundal (1999), Saether (2000), Vårdal et al. (2001), and Saether and Ekrem (2003) appear to be a result of dispersal rather than vicariance for all of the taxa mentioned.

The dispersal route between East Asia, the Russian Far East and North America across a former Beringian land bridge may be as recent as during the Quaternary Ice Age for some closely related species such as in the convictum group of Uresipedilum.

Uresipedilum has one species registered from Guatemala, another from Peru, while Pentapedilum has one species from Martinique and one from Brazil. Although few species, this may indicate that in Uresipedilum the species have dispersed across the Panama Isthmus like in most cold-stenothermic chironomids, while in Pentapedilum the dispersal has been taking placed across the Caribbean Ocean.