Original paper

Anostracan monopolisation of early successional phases in temporary waters?

Jocque, M.; Vanschoenwinkel, B.; Brendonck, L.


The length of the hydrocycle restrains the development of communities in temporary aquatic habitats. Little information is available on the importance of biotic interactions in shaping the communities in these habitats. A common observation in the freshwater rock pool community assembly process is the clearly separated density peaks of fairy shrimp (Anostraca) and cladocerans (Anomopoda) over time. Fairy shrimp (Anostraca), the flagship group and dominant filter feeders of temporary waters hatch early after inundation. This contrasts with the occurrence pattern of coexisting cladocerans, which despite higher chances of abortive hatching occur later during the hydroperiod. To study this apparent succession pattern and test the possible presence of a biotic interaction, we set up enclosure experiments in freshwater rock pools in Western Australia and monitored cladoceran (Macrothrix hardingii) densities in the presence of variable densities or absence of fairy shrimp (Branchinella longirostris). The anomopod cladoceran populations decreased with increasing anostracan densities revealing a negative biotic interaction. The competitive dominance of anostracans most probably was mainly due to exploitation competition, with possibly elements of interference competition or predation included. Early hatching and competitive superiority may help anostracans in temporary pools to monopolize the habitat with respect to small and/or other filter feeding invertebrates. As such they influence succession dynamics and invertebrate community structure, making anostracans keystone species of temporary pools.


anostracacladoceracompetitionrock poolsuccession