干旱区生态环境知识资源中心

The freshwater anostracan Branchipodopsis wolfi inhabits clusters of desert rock pools in southeastern Botswana. These rock pool sites are rare and occur in a matrix of unsuitable habitat for establishment. The temporal and spatial variability of such (partially isolated) habitats is expected to favour selection for dispersal. This paper reviews recent work on dispersal strategies in B. wolfi. By using egg traps at different sites and heights, direct proof was gathered that at least part of the egg bank of B. wolfi is dispersed by wind. Wind-borne dispersal of resting eggs could, however, only be confirmed at one site with shallow basins and with little vegetation cover and this only at saltation height. Long-range dispersal by wind is considered a rare event and mal-adaptive for rock pool inhabitants. To reduce loss of eggs by landing in unsuitable places, short-range dispersal by means of drought-resistant resting eggs is expected to be the selectively superior strategy, very much as atelechory in desert plants and reduced dispersal ability in animals and plants of oceanic islands. After inundation, part of the egg bank of B. wolfi floats and is considered to be an efficient means of short-range dispersal. Analysis of the genetic structure of three rock pool metapopulations supports our hypothesis on the dominance of short-range in comparison with long-range dispersal in B. wolfi. The production of sticky eggs that collect dirt within seconds after deposition is considered a case of anti-telechory to inhibit long-range dispersal. The generation of multi-year egg banks and mixed dispersal strategies allows B. wolfi to respond to unpredictable habitat availability/suitability in both time and space.