Aquatic fauna in a chain-of-ponds system: the influence of habitat features in a fragmented Victorian lowland river

This research project examines the influence of pond habitat features on aquatic fauna in a type of fluvial system fragmented in space and time. The chain-of-ponds system was once a common type of lowland river in southeastern Australia, consisting of an irregular pattern of different sized ponds separated by sections of empty channel. These different sized ponds exist along a large gradient in relative permanency with periodic high flows linking the ponds to form a continuous river system. I investigated whether these differences in pond size and spacing and other key environmental variables were important in determining faunal abundance and richness. Nineteen randomly selected ponds were surveyed for adult and larval dragonflies, mayflies, caddisflies, molluscs, shrimp, beetles and true bugs in a section of the Perry River chain-of-ponds system located within the Providence Ponds Flora and Fauna Reserve, in Gippsland, Victoria Collective measures of pond size, microhabitat type and pond isolation extracted from principal components analysis explained some of the variation in faunal distribution patterns. Size and microhabitat type (aquatic macrophyte cover) showed a stronger overall influence on faunal abundance than the other environmental variables. Species-area relationships could only be supported for overall taxon richness and the species richness of dragonfly larvae. It is hypothesised that a lack of other significant relationships between pond fauna and other environmental variables occurs due to the presence of the introduced mosquito fish (Gambusia holbrooki), the role of chance colonisation in determining distribution patterns and the generalist adaptations of the fauna. This research highlights that a range of habitat sizes existing on both spatial and temporal scales and other stochastic factors may be critical for maintaining the persistence of the different types of fauna in this chain-of-ponds system