Assessing the ecological value of small testate amoebae (<45 μm) in New Zealand peatlands

Abstract

Methodological advances are essential for robust ecological research. Quantitative reconstructions of environmental conditions using testate amoebae rely on sound taxonomy. While the taxonomy of large species is relatively well resolved, this is not the case for most small taxa (typically <45 m long). In New Zealand, peatlands contain a diversity of both cosmopolitan and characteristic large southern endemic taxa, but also have a high abundance of small taxa. The latter are often lumped into morphotypes reducing their value as ecological indicators. In this study, we demonstrate how (a) lumping small taxa versus splitting them into unique types, and (b) including or excluding them from community analysis influenced their ecological inference. We assessed testate amoeba composition in six peat bogs from New Zealand, three that were moderately-to-highly impacted, and three that were non-impacted. Environmental variables were measured at each sampling site and the surface testate amoeba community patterns and community-environment relationships compared. We found a clear division between impacted and non-impacted sites. Several distinct small taxa were more strongly related to water-table depth and conductivity, while the larger taxa were more correlated to pH. These results show that improved taxonomic resolution of small taxa can provide more informed environmental assessment.

Testate Amoeba Functional Traits and Their Use in Paleoecology

“…Several observations and experiments have shown that the size of testate amoeba tests may be controlled by hydrological conditions, which suggests that species with small tests are probably better adapted to survive under dry conditions (see McKeown et al, 2019). Therefore, in peat cores, an observed shift in the dominant test size of testate amoebae may indicate a change in hydrology (or other relevant environmental factor), as confirmed by two paleoecological studies.…”

“…In a study of subalpine peatlands covering the full bog to rich fen gradient, the species richness of testate amoebae was highest in calcium-rich and extremely calcium-rich fens when compared to calcium-poor fens and bogs (Lamentowicz et al, 2010). New Zealand peatlands in contrast, are characterized by higher relative abundances of small taxa in areas at the acidic end of the pH gradient (pH 4.0-4.5) as well as in wetter habitats (DWT −10 to 20 cm), as compared to higher pH (5.0-5.5) and drier habitats (DWT 25-50 cm; McKeown et al, 2019). These results clearly indicate the need for more detailed studies on determining the nature of testate amoebaenvironment relationships in fens.…”

“…In New Zealand peatlands, smaller species were found to be more closely correlated to water table depth and conductivity while larger species were correlated to pH, suggesting that these two components of the community may provide contrasting ecological signals (McKeown et al, 2019). Among direct anthropogenic impacts, atmospheric pollution has been shown to negatively influence high trophic level testate amoeba species (Meyer et al, 2012(Meyer et al, , 2013, again emphasizing the generally higher sensitivity of larger testate amoeba taxa to environmental disturbances (Table 1).…”

“…However, the application of this classification in subsequent functional ecology studies was limited. Lousier, 1974;Wanner and Xylander, 2005;Laggoun-Défarge et al, 2008;Fournier et al, 2012Fournier et al, , 2015Jassey et al, 2013aJassey et al, ,b, 2016Fiałkiewicz-Kozieł et al, 2015;Lamentowicz et al, 2015;Arrieira et al, 2016;Krashevska et al, 2016Krashevska et al, , 2020Marcisz et al, 2016, Marcisz et al, 2020Gałka et al, 2017;Koenig et al, 2017Koenig et al, , 2018aMcKeown et al, 2019;Macumber et al, 2020 Length/size/shell size (µm) Lamentowicz et al, 2009a;Fournier et al, 2012;Gomaa et al, 2012;Fiałkiewicz-Kozieł et al, 2015;Krashevska et al, 2016Krashevska et al, , 2020Schwind et al, 2016a,b;Koenig et al, 2017Koenig et al, , 2018avan Bellen et al, 2018;Marcisz et al, 2019 Frontiers in Ecology and Evolution | www.frontiersin.org No Gomaa et al, 2012;Lansac-Tôha et al, 2014;Lahr et al, 2019;Krashevska et al, 2020;Macumber et al, 2020 Lousier, 1974;Fournier et al, 2012Fournier et al, , 2015Fournier et al, , 2016…”

Superficially described and ignored for 92 years, rediscovered and emended: Apodera angatakere (Amoebozoa: Arcellinida: Hyalospheniformes) is a new flagship testate amoeba taxon from Aotearoa (New Zealand)

“…Since then, to our knowledge 19 studies were published on the diversity and ecology of testate amoebae of New Zealand, reviewed in McKeown et al ( 2021 ). A limited number of studies described new species for science, new records for New Zealand or, more recently, focused primarily on the community ecology of testate amoebae and their application in paleoecology (Bamforth, 2015 ; Charman, 1997 ; Deevey, 1955 ; Hoogenraad & de Groot, 1948 ; McGlone & Wilmshurst, 1999 ; McKeown et al, 2019 ; van Oye, 1956 ; Stout, 1984 ; Wilmshurst et al, 2002 , 2003 ; Winterbourn & Brown, 1967 ). However, there has been no modern study on testate amoeba taxonomy that incorporates molecular, morphometrical and ecological data, which are required to accurately describe new species (Lara et al, 2020 ).…”