Interpreting Morphologically Homogeneous (Paleo-)Populations as Ecological Species Enables Comparison of Living and Fossil Organism Groups, Exemplified by Nummulitid Foraminifera

Morphologically homogeneous groups, either living populations or fossil paleo-populations, must be regarded as ecological species, independent of their molecular genetic resemblance in living forms. Morphology is always expressed during development by structure genes initiated from a network of regulator genes acting at different times and intensities, additionally being subjected to epigenetic controls. Therefore, homogeneous populations influenced by the environment represent species better than the reproduction (biological species) or molecular-genetic approach using ancestral sequences like rDNA. Living and fossil representatives of nummulitid foraminifera were chosen to demonstrate complete reconstruction of morphology using metrical growth-invariant and growth-independent characters. Using these characters, 6 models were established to define ecological species in living and fossil species. Furthermore, a distinction between evolutionary and environmental effects in fossil forms was possible using discriminant analysis showing characters that are responsible for differentiating between evolutionary and environmental trends.