Fundamental and Applied Limnology vol:176 issue:2 pages:127-132
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 fl agship
group and dominant fi lter 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 fi lter
feeding invertebrates. As such they infl uence succession dynamics and invertebrate community structure, making
anostracans keystone species of temporary pools.