Molecular characterization of the non-costate morphotypes of buliminid foraminifers based on internal transcribed region of ribosomal DNA (ITS rDNA) sequence data

We performed molecular phylogenetic analyses of four morphotypes of the benthic foraminiferal genus Bulimina (B. aculeata, B. marginata f. marginata, B. marginata f. denudata, and B. elongata) based on sequences of internal transcribed spacer region of ribosomal DNA (ITS rDNA). Six genetically distinct phylotypes were revealed by our phylogenetic analyses. The six phylotypes basically correspond to the fundamental morphotypes: clades A + B (B. aculeata); clade C (B. elongata); clade D (B. marginata f. denudata); clade E (B. marginata f. marginata genotype 1); and clade F (B. marginata f. marginata genotype 2). All six phylotypes are well distinguished, except phylotype B, which shows only little sequence divergence compared to clade A, possibly indicating that genetic differentiation is in progress. Morphological characters including the direction, placement, and shape of spines, the angle of undercutting of chamber periphery, and the roundness of the chambers were stable among specimens of each clade. In contrast, the length and density of spines, and chamber size, were variable within each clade. These intermediate morphological characters may reflect ecophenotypic variation. Our study clearly shows that the examined B. acuelata, elongata, and denudata morphospecies are genetically separated and that B. marginata is a species complex comprising several genotypes. A novel phylotype represent different morphotype compare to B. marginata f. marginata that can be distinguished based on differences of chamber angularity, the direction, placement, and shape of spines, and test dimensions.