Clément Duckert

Most eukaryotic microbial biodiversity is undescribed, and most species might be morphologically indistinguishable. Notable exceptions are so-called flagship species which are highly conspicuous and can therefore be used to address biogeographical questions. Here we describe Hyalosphenia papilio subsp. paynei, an arcellinid testate amoeba (Amoebozoa; Arcellinida; Hyalospheniidae) from wet hollows in two Sphagnum peatlands, one in Wales and one in Ireland. Phylogenetic analysis based on Cytochrome C oxidase subunit I (COI) sequencing places it within the lineage A of the H. papilio complex, but it differs from all 13 known H. papilio genetic lineages by its very distinctive, wider than long, morphology. The fact that such a conspicuous taxon was never reported in hundreds of studies published on Holarctic Sphagnum peatlands since Leidy’s description of H. papilio in 1874 suggests that this subspecies has not dispersed and survived beyond Britain and Ireland. Furthermore its genetic similarity to H. papilio s. str. suggests that it has recently evolved. The discovery of this new taxon calls for a more detailed analysis of the morphological, ecological and molecular diversity of the H. papilio species complex.

Microbial diversity is known to be huge but remains only partly documented. Testate amoebae are a relatively well studied group or free-living protists that build morphologically characteristic shells on which the taxonomy of this group is mainly based. Among testate amoebae, the Hyalospheniformes are especially well documented and are a model group for microbial biogeography. Here we describe a new species of genus Certesella from Sphagnum mosses and forest litter samples collected in the Dominican Republic and Chile. We name this species Certesella larai to honour our esteemed colleague Enrique Lara. This species bears two large pores connected by tube, which are characteristic of the genera Porosia and Certesella. The new species fits best in the latter genus given the presence of a distinct, sometimes denticulated, neck with a bulge that is absent in genus Porosia but occurs in Certesella. Its elongated shape (length/breadth ratio 2.03–2.58) only overlaps with C. certesi, which is distinguishable by the presence of a distinct longitudinal groove in the neck region that is absent from the new species. Interestingly most specimens lacked the internal teeth which are usually present in members of genus Certesella. As such, while the morphology of C. larai strongly suggests a belonging to genus Certesella, molecular analyses are still required to confirm its phylogenetic position, clarify the relationships among all species in genera Porosia and Certesella and the definition and validity of these two genera. The presence of this new species in two rather distant regions – Caribbean and central Chile – suggests it is likely widespread, but possibly rare. However, this perception may be due to a sampling bias in favour of Sphagnum mosses and wet and organic-rich habitats. This illustrates the need for a more systematic sampling effort to document the full and mostly unknown taxonomic diversity of soil protists.