Ecology of testate amoebae (Protista) in south-central Alaska peatlands: building transfer-function models for palaeoenvironmental studies

Abstract

Testate amoebae are valuable indicators of peatland hydrology and have been used in many palaeoclimatic studies in peatlands. Because the species' ecological optima may vary around the globe, the development of transfer function models is an essential prerequisite for regional palaeoclimatic studies using testate amoebae. We investigated testate amoebae ecology in nine peatlands covering a 250-km north-south transect in south-central Alaska. Redundancy analysis and Mantel tests were used to establish the relationship between the measured environmental variables (water-table depth and pH) and testate amoebae communities. Transfer-function models were developed using weighted averaging, weighted average partial least squares and maximum likelihood techniques. Model prediction error was initially 15.8 cm for water-table depth and 0.3 for pH but this was reduced to 9.7 cm and 0.2 by selective data exclusion. The relatively poor model performance compared with previous studies may be explained by the limitations of one-off water-table measurements, the very large environmental gradients covered and by recent climatic change in the study area. The environmental preferences of testate amoebae species agree well with previous studies in other regions. This study supports the use of testate amoebae in palaeoclimate studies and provides the first testate amoebae transfer function from Alaska.

SSU rRNA Reveals a Sequential Increase in Shell Complexity Among the Euglyphid Testate Amoebae (Rhizaria: Euglyphida)

“…3), form a well-supported clade. This is also consistent with their morphology and ecology: these are three large spiny species which are often found in wet forest mosses, the larger E. compressa being especially abundant in wet Sphagnum habitats (Booth 2001;Charman and Warner 1992;Lamentowicz and Mitchell 2005;Mitchell et al 1999;Payne et al 2006). Euglypha cf.…”

Ecology of Testate Amoebae from Mires in the Central Rhodope Mountains, Greece and Development of a Transfer Function for Palaeohydrological Reconstruction

“…For pH a weighted average model performs best by both RMSEP jack and RMSEP boot . Model performance is consistent across the hydrological gradient without the under-prediction of water table depths for the driest sites seen in previous studies (Mitchell et al 1999;Payne et al 2006;Fig. 6).…”

“…Samples with residuals greater than 3.5 cm were excluded from the water table data and samples with residuals greater than 0.6 from the pH data. These cut-off points represent approximately 20% of the total environmental gradients, a similar proportion to some previous studies (Charman 1997; Payne et al 2006). Using these filtered data RMSEP boot is reduced to 1.93 cm for water table depth and 0.35 for pH at the expense of reducing the number of samples to 57 for DWT and 56 for pH (Table 4).…”

“…In absolute terms this is the best performing testate amoebae hydrological transfer function yet produced. The eight previous studies, which have presented RMSEP jack results, show optimum values between 3.9 and 9.7 cm (Payne et al 2006;Woodland et al 1998). However, there is a general correlation between model performance and total environmental gradient (Payne et al 2006).…”

“…Transfer function models for hydrology have now been developed from regions around the world with the greatest concentration in North America and northern and central Europe (Bobrov et al 1999;Booth 2001Booth , 2002Warner 1992, 1997;Lamentowicz and Mitchell 2005;Mitchell et al 1999;Payne et al 2006;Tolonen et al 1994;Warner and Charman 1994;Wilmshurst et al 2003;Woodland et al 1998). However, there have been no quantitative studies of testate amoebae in peatlands in southern Europe or more arid regions in general.…”