Temporal priority and intra-guild predation in temporary waters: an experimental study using Namibian desert dragonflies

Abstract. 1. Intra-guild predation between early larval instars of two co-existing dragonflies, Sympetrum fonscolombii and Trithemis kirbyi , was investigated with respect to temporal advantage and growth. Three situations were simulated experimentally: (1) Sympetrum fonscolombii began development 11 days before T. kirbyi . (2) Trithemis kirbyi began development 11 days before S. fonscolombii . (3) Both species began on the same day.
2. With a temporal advantage of 11 days to the second species, the resulting larval density of the respective first species was significantly higher than that of the second species.
3. Without a temporal advantage, the survival of S. fonscolombii was higher than that of T. kirbyi , and S. fonscolombii had a larger size due to faster growth than T. kirbyi . Hence, it is assumed that survival depended on early oviposition as well as on larval growth.
4. To test the relevance of the laboratory results, observations at artificial ponds in the Namibian semi-desert were conducted. Trithemis kirbyi was the first species colonising these ponds while S. fonscolombii arrived 15 days later. In field samples, many more Trithemis larvae than Sympetrum larvae were found, a pattern similar to the laboratory experiments in which T. kirbyi enjoyed a temporal advantage.