Multiple convergences in the evolutionary history of the testate amoeba family Arcellidae (Amoebozoa: Arcellinida: Sphaerothecina): when the ecology rules the morphology

Protists are probably the most species-rich eukaryotes, yet their systematics are inaccurate, leading to an underestimation of their actual diversity. Arcellinida (= lobose testate amoebae) are amoebozoans that build a test (a hard shell) whose shape and composition are taxonomically informative. One of the most successful groups is Arcellidae, a family found worldwide in many freshwater and terrestrial environments where they are indicators of environmental quality. However, the systematics of the family is based on works published nearly a century ago. We re-evaluated the systematics based on single-cell barcoding, morphological and ecological data. Overall, test shape appears to be more related to environmental characteristics than to the species’ phylogenetic position. We show several convergences in organisms with similar ecology, some traditionally described species being paraphyletic. Based on conservative traits, we review the synapomorphies of the infraorder Sphaerothecina, compile a list of synonyms and describe a new genus Galeripora, with five new combinations. Seven new species: Arcella guadarramensis sp. nov., Galeripora balari sp. nov., Galeripora bufonipellita sp. nov., Galeripora galeriformis sp. nov., Galeripora naiadis sp. nov., Galeripora sitiens sp. nov. and Galeripora succelli sp. nov. are also described here.This work was funded by the Spanish Government PGC2018-094660-B-I00 (MCIU/AEI/FEDER,UE) and the program ‘Atracción de Talento Investigador’, grant awarded by the Consejería de Educación, Juventud y Deporte, Comunidad de Madrid (Spain) (2017-T1/AMB-5210).Peer reviewe