Biodiversity of Amphipods in the Solitary Islands New South Wales, Australia

Abstract

The biodiversity of amphipods in the Solitary Islands, New South Wales, Australia, was investigated using an experimental approach. A series of ecological experiments explored: 1) the variation in amphipod assemblages on natural habitats with depth; 2) colonization of a range of artificial substrate unit (ASU) types (all comprising small, complex plastic units), over deployment times ranging from one to sixteen weeks; and 3) variation in amphipod assemblages with different habitat architectures of the ASU types. The results from these experiments were then used to develop an efficient, ASU-based sampling package for rapidly assessing and cataloguing epifaunal amphipod biodiversity. Finally, taxonomic descriptions are given for new species collected during the study. The initial experiment indicated that trends in amphipod species richness along a depth gradient (4-14 m) varied with exposure and location. At Split Solitary Island, shallow depths generally supported the highest species richness, while at Korffs Islet, this occurred at greater depths. Though trends differed between sampling sites, species richness showed bimodality for most locations; samples from 10m, however, were most often associated with the highest species richness. Following this, a series of six different ASU types were deployed at 10m for colonization periods of one, two, four, eight and sixteen weeks at four locations (North Solitary Island, North West Solitary Island, Muttonbird Island and Korffs Islet). Amphipods readily colonized ASUs, with different ASU types colonized at different rates and, again, with variable trends across locations. Overall, samples from the four-week deployment supported the most species-rich assemblages across locations. Using data from the four-week deployment period, I next investigated the differences in assemblages between ASU type with the objective of assembling an optimum package for rapidly sampling the available amphipod biodiversity at a location. While significant differences were found between ASU types within locations, recruiting assemblages more closely reflected location-specific differences when compared across the four island locations. A combination of five of the original six ASU types (Onion bag, Shower poofie, Rope fibre and Astro turf) proved to be the most efficient package that consistently collected the highest species richness across all locations. In addition, this ASU sampling package consistently collected more amphipod species than were found in extensive collections of natural habitats at each location. Assemblages recruiting to the sampling package were strongly representative of the local and regional species pool when compared to master lists compiled from all available records (including museum records and data from previous studies in the region).