MODULARITY AND EVOLUTION IN FORAMINIFERA

A phylogenetic hypothesis of the evolutionary relationships of Recent and fossil foraminiferans, generated from a morphological data matrix, was used as a framework to examine the major evolutionary trends in the clade Foraminifera. One of the more significant trends observed in the evolutionary history of Foraminifera appears to be the acquisition of modularity, a concept defined in the literature as “the division of biological structure into standardized and repeatable parts.” Modularity is considered to have played an important role in the evolution of complexity in the multicellular eukaryotic clades, such as animals and plants; however, foraminiferans may be unique among unicellular eukaryotes in having evolved complex modular morphological structures. The different modules observed in foraminiferans include: chambers in multichambered taxa, nuclei in multinucleate forms, apertures and apertural complexes, life history stages, and endosymbiotic associations with unicellular photosynthetic eukaryotes. The evolutionary significance of these different types of modularity will be discussed from within a phylogenetic context.