Behaviour and growth of dragonfly larvae along a permanent to temporary water habitat gradient.pdf

Behaviour and growth of dragonfly larvae along a permanent to temporary water habitat gradient FRANK JOHANSSON1 and FRANK SUHL ING2 1Department of Ecology and Environmental Science, Umea? University, Sweden and 2Institute of Zoology, Technische Universita?t Braunschweig, Fasanenstrasse, Braunschweig, Germany Abstract. 1. Freshwaters form a gradient from small temporary waters to large permanent waters. Identifying and examining traits that restrict the distribution of species along this gradient are crucial to the understanding of community struc- ture in these habitats. 2. Using dragonfly larvae species, differences in traits important for growth and survival were studied. 3. The traits were studied in a series of laboratory experiments using two pairs of dragonfly species that coexist in the Namibian semi-desert. One species pair was from the most temporary part of the water permanence gradient and the other species pair from an intermediate part of the gradient. 4. As predicted, activity, capture rate, and growth rate were significantly greater in the two temporary water species. Contrary to the prediction made in the work reported here, species differences in microhabitat selection were not related to the species’ habitat origin. Cannibalism did not differ between species. 5. The results lend support to the hypothesis that selection has favoured certain combinations of trait values and that these traits are important for a successful life in temporary and permanent waters. Keywords. Activity, growth rate, life history, Odonata, temporary pools. Introduction The distribution patterns of species are usually governed by habitat requirements and spatial aspect of population dynamics. While macroecology studies large-scale distribu- tion patterns (Brown, 1995), behavioural and life-history ecology studies adaptation to environments at a much finer scale (Wellborn et al., 1996). In this study the latter is focused on. Aquatic systems can be classified into a number of