The Odonata of some saline lakes in British Columbia, Canada: ecological distribution and zoogeography

The Odonata of a series of 18 lakes on the Chilcotin Plateau of central British Columbia were examined. The lakes have similar temperature profiles, but differ widely in chemical composition and vegetation characteristics. Salinity, as measured by surface conductivity, ranges from 72 to 15524 microSiemens/cm at 25°C; the main cations are sodium and magnesium and the main anions are carbonate and bicarbonate. — Twenty-two species were found in the lake series; evidence for breeding was found for nineteen species. The distribution pattern of these species is that of a primarily freshwater group containing a few taxa that can tolerate moderate or higher salinities. No species was restricted to the higher salinity lakes. This pattern is in contrast to those of the aquatic Hemiptera and Coleoptera of the same lakes, which have very few species restricted to the fresh lakes and have some taxa restricted to the saline lakes. Cluster analysis divided the breeding fauna into three general groups: one of six common species tolerant of salinities exceeding 4000 µS/cm, one of three common species tolerant of moderate salinities (up to 1600 µS/cm), and five less common species restricted to lakes with conductivities less than 1300 pS/cm. The remaining five species had very local distributions in the fresher lakes and did not form a cluster. — The species composition reflects a predominantly northern origin of the fauna; 72% of the species have Holarctic or Boreal ranges.