Behavioural differences in response to current: implications for the longitudinal distribution of stream odonates
published: May 23, 2005
ArtNo. ESP141016371005, Price: 29.00 €
Different longitudinal distribution patterns occur in closely related running water species. However, the mechanisms that underlie this phenomenon are poorly studied. In European Cordulegaster species (Odonata) two different longitudinal distribution patterns occur: species like C. bidentata and C. insignis are limited to springs and springbrooks, whereas species like C. boltonii and C. picta are less restricted and occur from springs to larger streams and rivulets. To find an explanation for these patterns, experiments in artificial streams were carried out to reveal differences in larval response to current between species of the two types. Larval C. bidentata and C. insignis showed a higher proneness to drift compared to C. boltonii and C. picta. Furthermore, C. bidentata and C. insignis avoided renewed drifting after a forced drift event less effectively and, exposed to strong current, travelled longer distances. It is concluded that, compared to the other pair of species, the behavioural traits of C. bidentata and C. insignis are less effective to withstand strong hydraulic stress, which restricts the distribution of these species to habitats with low discharge and current velocity, namely springs and springbrooks.