Hommersand, Gensel, and Volovsek The "lower florideophytes" consist of a diverse assemblage of red algal families and orders with representatives in marine and fresh water habitats throughout the world. Many occur in tropical areas in close association with other organisms, often as epiphytes or endophytes. A few, such as dulse, can be conspicuous members of marine boreal ecosystems and have been an important part of the local human diet. Like all typical florideophyte algae, the lower florideophytes display a remarkable triphasic life history and a unique structure called the pit-plug, a cellular connection which results from incomplete cytokinesis. The group differs from the higher florideophytes by possessing comparatively simple reproductive and vegetative morphologies, unique patterns of mitosis and cytokinesis, and a diverse array of life histories, photosynthetic pigments and pit-plug types. Some lower florideophyte features have been interpreted as primitive, suggesting that the group may be transitional between the putative oldest red algal assemblage, the bangiophytes, and the more advanced florideophytes. The higher level taxonomy of this group has been problematic, and even though recent emphasis on pit plug ultrastructure has provided some clarification, conflicting characters continue to frustrate attempts to achieve a natural classification. This study by graduate student Miguel Volovsek, under the supervision of Dr. Max Hommersand and Dr. Pat Gensel at University of North Carolina, aims to identify ordinal and familial level groups among the lower florideophytes and to assess their phylogenetic relationships by using independent molecular evidence from the chloroplast rbcL and 23S rDNA gene sequences. Diagnostic features for each group will be explored with morphological techniques, concentrating on understudied representatives. Because of the important taxonomic position occupied by the lower florideophytes, this research will provide a framework for interpreting life histories and vegetative and reproductive features across the red algae.
