Freshwater bryozoans (Bryozoa) of Norway II: distribution and ecology of two species of Fredericella

摘要: Freshwater bryozoans were investigated during field studies of 601 lakes and other surface water bodies throughout Norway from 1960 to 1978. The frequency occurrence the two Fredericella species was evaluated in relation 12 environmental variables. Statistically significant deviations frequencies expected on basis random distribution described using categories preference, avoidance absence. typical European sultana (with glossy statoblasts) occurred at 72 localities, north 70° 25′ N (the northernmost record a global scale). Its dropped towards north. Maximum elevation above sea level 1097 m (maximum recorded for Northern Europe). Another with pitted statoblasts, tentatively considered be indica, 50 71° 09′ reported date). geographical reflected northern cold-water species. One third records situated Arctic Circle, rich colonies found North Cape plateau, as far possible mainland. few southeastern high mountain lakes, up 1397 (highest This not any numerous lowland where F. common. Both tolerated cold climate, especially they wide range environments. preferred rather low level, vegetation plant eutrophic environments, gyttja sediments stony "hard" shores, some wave action, content calcium, slightly coloured water. avoided ponds absent ditches mires, dystrophic surrounded by Sphagnum bog, dy strongly water, sites small indifferent magnesium concentrations pH below 5.4. indica only lakes. It temperatures, oligotrophic conditions poor aquatic 7.0, colour (below 11 mg Pt l−1). temperatures 20 °C, or consisted soft dygyttja dy, places acid 5.9, tended avoid 10 l−1 40 l−1. together six four north, southern areas. opposite sensitivity reactions several variables supported logistic regression analysis. main ecological difference between is that appears more dependent climatic factors.