A multivariate statistical determination of some recent morphospecies of the genus Elphidium from Gulf of Mexico



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An analysis involving a set of 15 variables on each of 212 specimens of the genus Elphidium sub-equally distributed among 7 samples from the north-western Gulf of Mexico results in 6 groups which are both observationally and statistically distinct. These 6 groups correspond to 9 previously described species. The raw data are subjected to the following series of multivariate statistical techniques: 1. Statistical normalization (Z-form) and data condensation (factor analysis) 2. Formation of protogroups and a residual pool of ungrouped specimens (geometric distance) 3. Addition of ungrouped specimens to protogroups and verification of groupings (discriminant analysis) 4. Combination of protogroups (canonical variates or graphical technique) 5. Procedures 3 and 4 are repeated until no more specimens can be added to the protogroups and no more protogroups can be combined. The resulting sets of specimens are the final statistical morphospecies. The original 9 species are reduced to 5 species: Elphidium discoidale, E. galvestonense, E. gunteri, E. incertum and E. poeyanum. Elphidium matagordanum is provisionally considered a junior synonym of E. incertum mexicanum; Cribroelphidium poeyanum, Elphidium delicatulum and E. translucens are provisionally considered junior synonyms of E. poeyanum. Geographic distributions of the groups in this study indicate that there may be three faunal areas of Elphidium in the Gulf of Mexico: the northern Gulf characterized by E. gunteri, the western Gulf characterized by E. discoidale and E. galvestonense, and the southern Gulf characterized by E. incerturn mexicanum.