Molecular phylogeny of Elphidiidae (foraminifera)

• Phylogenetic analysis of 17 morphospecies of Elphidiidae and their close relatives.
• Six highly supported clades are identified.
• Molecular taxonomy (SSU rDNA) shows many discrepancies with current taxonomic system.
• This study challenges species, genus and family level classifications.
• Answers to important questions regarding classification of elphidiids are proposed.

The Elphidiidae represent one of the most abundant and diversified foraminiferal family in shallow water habitats worldwide. Playing crucial roles in diverse ecosystems, they occur since the Eocene to present and are widely used for paleoenvironmental reconstructions. However, the lack of a clear taxonomic consensus led to a vast confusion concerning the relation of Elphidiidae with other rotaliids, in particular Nonionidae (Haynesina) and Rotaliidae (Ammonia). Moreover, high morphological plasticity of the test prevented the establishment of a clear definition for many species and genera of this family. Here, 66 new sequences of the SSU rRNA gene were obtained and used to build an extensive dataset including 94 complete or partial sequences of the SSU rDNA of 17 different morphospecies of Elphidiidae, Haynesina and Ammonia. Phylogenetic analyses of this dataset allowed identifying six strongly supported clades. Comparison of these molecular clades with the morphological characters of the analyzed individuals showed major discrepancies with the current taxonomic system. The relations between the six clades depended on the selection of the outgroup to the Elphidiidae. For biological and morphological reasons, we privileged here the choice of Ammonia, prompting the inclusion of Haynesina to the family Elphidiidae. However, this does not necessarily imply a monophyletic origin of all these taxa. In fact, we cannot exclude that Elphidiidae as they are defined here are paraphyletic and that Ammonia as well as some other rotaliids are branching within them.