Testate amoebae as paleoenvironmental indicators in peatlands: calibration-dataset synthesis and assessment of modern analogues using the Neotoma Paleoecology Database

Testate amoebae are widely used paleoindicators of past environmental conditions, particularly in peatlands where they have been used as surface-moisture proxies. Modern ecological studies of the past several decades inform the interpretation of stratigraphic records, and increasingly both modern surface-sample datasets and stratigraphic records are being added to publicly available databases like the Neotoma Paleoecology Database. In this paper, we broadly synthesize results of calibration studies during the past ∼35 years, and then use data from the Neotoma Paleoecology Database to examine morphospecies-environment relationships in calibration datasets from the northern hemisphere and directly compare subfossil and modern testate amoeba communities to assess the strength of modern analogues for subfossil samples in North American stratigraphic records. Results confirm the consistent and central importance of surface-moisture in controlling testate amoeba communities in peatlands, with similar community-moisture relationships across the Northern Hemisphere. However, many subfossil communities have few good modern analogues, likely due to a combination of factors including differential decomposition of taxa extending beyond the well-documented poor preservation of weakly idiosomic tests. Many subfossil samples contain high abundances and unusual combinations of taxa that are not well represented in modern datasets, and the causes and implications of subfossil communities with poor modern analogues deserve greater attention by the research community. The Neotoma Paleoecology Database is a valuable shared resource, and its continued development will enable the examination of research questions focused on understanding the variability and structure of modern and subfossil testate amoeba communities, as well as moisture reconstructions in both time and space. • Surface-moisture is a critical control on the composition of testate amoeba communities in peatlands. • Similar community-moisture relationships occur across the Northern Hemisphere. • Many subfossil communities have few good modern analogues. • Differential decomposition of taxa likely extends beyond the well-documented poor preservation of weakly idiosomic tests. • Causes and implications of subfossil communities with poor modern analogues deserve greater attention.