How to enter a desert - patterns of Odonata colonisation of arid Namibia

With a total of 75 species the odonate diversity in the Namibian desert is surprisingly high. Based on their distribution characteristics, invasion patterns, and breeding success, there are six well-defined categories of Odonata: widespread species - (1.) permanently living in the desert, and desert biased, (2) permanently living in the desert, but not desert-biased; (3) entering the desert seasonally; (4) entering from neighbouring tropical or temperate regions, whose populations may breed in the desert sometimes or locally. Category (5) consists of species with highly localised breeding Populations in the desert, which are widely isolated from potential source populations. The last category (6) consists of species restricted to allochthonous perennial rivers. We discuss these patterns from a geographical and a temporal perspective. On the one hand, there have been different spatial directions from where species have entered deserts. On the other hand, Odonate distribution patterns in the deserts have a palaeoclimatic as well as a present time perspective, the latter with seasonal and annual fluctuations and a strong influx from neighbouring biomes. The discovery of a desert-bias in several species suggests that odonates could be well adapted to desert conditions or, in other words, some species of odonates may be promoted by and conditions.