Cryptic Diversity within Morphospecies of Testate Amoebae (Amoebozoa: Arcellinida) in New England Bogs and Fens

Testate (shelled) amoebae are abundant and diverse in Sphagnum-rich areas of bogs and fens. Test morphology is standardly used to identify morphospecies as tests have varying shapes and compositions (e.g. siliceous, proteinaceous, agglutinated, or even calcareous). The recent application of molecular tools has revealed a greater complexity than morphology suggests, including multiple cryptic species. Here, we assess the biodiversity and relationships among eight morphospecies: Hyalosphenia elegans, Hyalosphenia papilio, Nebela carinata, Nebela flabellulum, Nebela militaris, Nebela tincta, Nebela tubulosa, and Quadrulella symmetrica using small subunit ribosomal DNA (SSU-rDNA). An SSU-rDNA phylogeny including 20 specimens from GenBank and 63 from this study reveals diversity within and among morphospecies and low resolution among some Nebela spp. Previous SSU-rDNA work on a limited sample of these species showed non-monophyly in the genus Hyalosphenia. Our analyses confirm this pattern and further suggest that other Nebela genera and morphospecies are not monophyletic. Moreover, inclusion of up to 24 specimens per species indicates non-monophyly of the morphospecies Hyalosphenia papilio and Hyalosphenia elegans. Our results suggest the morphological plasticity of testate amoebae across evolutionary time scales and that a combination of morphology and molecular analyses is needed to understand the biodiversity of these taxa.