Modelling hydrological relationships of testate amoebae (Protozoa: Rhizopoda) on New Zealand peatlands

Research in the Northern Hemisphere shows the principal control on species distribution and abundance of testate amoebae to be local hydrology, which in ombrotrophic mires is linked directly to climate. Fossil faunas can therefore be used to infer past hydrological and climatic conditions. This study investigates whether a similar relationship can be found for New Zealand peatlands, as a first step towards developing a method for palaeomoisture reconstructions. Fifty-seven samples from 13 peatlands were analysed for testate amoebae and related to site hydrology, pH and conductivity of mire waters, climate, and vegetation type using canonical correspondence analysis (CCA). Water table and soil moisture were the dominant factors, and their relationship with species assemblage was modelled using four transfer functions: weighted averaging (WA), tolerance downweighted weighted averaging (WA-Tol), partial least squares (PLS), and weighted average partial least squares (WA-PLS). PLS and WA-PLS performed best, and suggest that palaeohydrology could be accurately inferred from fossil faunas. Results are contrasted with those found in the northern peatlands.