Systematics and Taxonomy
The family Capniidae is often considered to be monotypic as to subfamily, with the Capniinae being inserted at that rank. However, this is rather pointless; in any case the phylogeny, systematics and taxonomy of the small winter stoneflies are highly confused. There appear to be two very basal genera and presumably two larger clades which conceivably could be considered subfamilies. But the phylogeny of the Capniidae is by no means robustly resolved, with about one-third of the named genera of uncertain position. Hence, any subdivision beyond the generic level is premature.
Furthermore, the type genus Capnia is probably not monophyletic and in serious need of splitting up. The type species Capnia nigra and its closest relatives would retain their genus name; they are closely related to Capnura. The North American species at least for the largest part are closer to Mesocapnia; other "Capnia" are closest to Bolshecapnia as it seems. Finally, there is a fourth group of rather uncertain position in the main assemblage of Capniidae.
A rough layout of the suspected phylogeny can be given as follows:
Basal genera
- Isocapnia
- Paracapnia
Suspected clade/subfamily 1
- Nemocapnia
- Capnioneura
- Eucapnopsis
Suspected clade 2/subfamily Capniinae sensu stricto
- Bolshecapnia
- Allocapnia
- Baikaloperla
- Capnia (paraphyletic)
- Capnura
- Utacapnia
- Mesocapnia
Incertae sedis as to clade 1 or 2
- Allocapniella
- Capniella
- Capnopsis
- Eocapnia
- Takagripopteryx
- Some species presently in Capnia
Read more about this topic: Capniidae