Pocheina and Acrasis are two genera of heterolobosean sorocarpic amoebae within Acrasidae that have historically been considered close relatives. The two genera were differentiated based on their differing fruiting body morphologies. The validity of this taxonomic distinction was challenged when a SSU rRNA phylogenetic study placed an isolate morphologically identified as "Pocheina" rosea within a clade of Acrasis rosea isolates. The authors speculated that pocheinoid fruiting body morphology might be the result of aberrant Ac. rosea fruiting body development, which, if true, would nullify this taxonomic distinction between genera. To clarify Acrasidae systematics, we analyzed SSU rRNA and ITS region sequences from multiple isolates of Pocheina, Acrasis, and Allovahlkampfia generated by Polymerase Chain Reaction (PCR) and transcriptomics. We demonstrate that the initial SSU sequence attributed to "P. rosea" originated from an Ac. rosea DNA contamination in its amplification reaction. Our analyses, based on morphology, SSU and 5.8S rRNA gene phylogenies, as well as comparative analyses of ITS1 and ITS2 sequences, resolve Acrasidae into three major lineages: Allovahlkampfia and the strongly supported clades comprising Pocheina and Acrasis. We confirm that the latter two genera can be identified by their fruiting body morphologies.
Keywords: Acrasis; Allovahlkampfia; Guttulina; acrasid; amoeba; cellular slime mold; multicellularity; protist; social amoeba; sorocarpic amoeba.
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