Abstract
Genetic characterisation (SSU rRNA genotyping) and Scanning Electron Microscope (SEM) imaging of individual tests were used in tandem to determine the modern species richness of the foraminiferal family Elphidiidae (Elphidium, Haynesina and related genera) across the Northeast Atlantic shelf biomes. Specimens were collected at 25 locations from the High Arctic to Iberia, and a total of 1013 individual specimens were successfully SEM imaged and genotyped. Phylogenetic analyses were carried out in combination with 28 other elphidiid sequences from GenBank and seventeen distinct elphidiid genetic types were identified within the sample set, seven being sequenced for the first time. Genetic types cluster into seven main clades which largely represent their general morphological character. Differences between genetic types at the genetic, morphological and biogeographic levels are indicative of species level distinction. Their biogeographic distributions, in combination with elphidiid SSU sequences from GenBank and high resolution images from the literature show that each of them exhibits species-specific rather than clade-specific biogeographies. Due to taxonomic uncertainty and divergent taxonomic concepts between schools, we believe that morphospecies names should not be placed onto molecular phylogenies unless both the morphology and genetic type have been linked to the formally named holotype, or equivalent. Based on strict morphological criteria, we advocate using only a three-stage approach to taxonomy for practical application in micropalaeontological studies. It comprises genotyping, the production of a formal morphological description of the SEM images associated with the genetic type and then the allocation of the most appropriate taxonomic name by comparison with the formal type description. Using this approach, we were able to apply taxonomic names to fifteen genetic types. One of the remaining two may be potentially cryptic, and one is undescribed in the literature. In general, the phylogeographic distribution is in agreement with our knowledge of the ecology and biogeographical distribution of the corresponding morphospecies, highlighting the generally robust taxonomic framework of the Elphidiidae in time and space.
Highlights
Very few of these sites would be available for phylogenetic analysis in a conservative alignment such as in this study, the variation is characterised by a set of fixed units typical for each variable region and which are unique to the genetic type (e.g., Supplementary Fig. S5)
If further specimens become available that allow S7 and S15 to be securely discriminated on their morphology, we suggest that S7 is the most similar to the specimen described and named as E. albiumbilicatum by Weiss (1954) and that S15 would require a new taxonomic name and description
Specimens of Elphidiidae were collected from 25 locations across the Northeast Atlantic from the Arctic to the Mediterranean, and 1013 were successfully Scanning Electron Microscope (SEM) imaged, genetically characterised and their distribution mapped
Summary
As for all calcareous foraminifera, elphidiid tests preserve readily and are important in reconstructing past marine environments. They have a well-known fossil record that extends as far back as the Eocene (Cushman, 1939) and have particular utility in stratigraphy, the reconstruction of Quaternary climate and sea-level cycles (e.g., Haslett, 2002; Murray, 2006). This utility largely derives from their widespread occurrence from the high to low latitudes and presence from the highintertidal to continental slope environments. The lack of carefully illustrated specimens in the literature makes it impossible to track the taxonomic concepts of these schools and their modifications, causing confusion for palaeoenvironmental studies
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