144 Use of Fourier Transform Infrared (FT IR) Diffuse Reflectance Spectroscopy and Hamming Distances to Study the Phycocolloid Chemosystematics of the Red Algae (Rhodophta)

The use of red algal polysaccharide cell wall structures as taxonomic indicators has been a recurring theme in the literature for over 58 years. Traditionally the polymeric phycocolloids of the red algal cell walls have been classified into definite structures (carrageenans and agars) based on the phycocolloids present. However, this method has some obvious shortcomings, such as its inability to assign hybrid structures (carragars), or the appearance of agarocolloids in traditional ‘carrageenophytes’. Thus, there is a need to develop an unbiased method of examining phycocolloid structures without assigning them names. Fourier transform infrared diffuse reflectance spectroscopy was used to analyze the spectra of a large number of red algal species, belonging to several orders. The spectra for each species resulted in a series of ‘peaks’ corresponding to certain wavenumbers (cm −1 ), which in term correspond to phycocolloid bonds. On the basis of shared/similar peaks, irrespective of their combinations to describe polymeric units, a series of matrices were developed for each family. These were coded as a 0 and 1, indicating the presence or absence of a peak, respectively. Using the concept of vector addition and Hamming distances, a methodology was formulated for analyzing ordinal and familial level groupings. Initial analysis on 173 species, representing 39 families and 12 orders of the Rhodophyta, proved to be promising. Some results corroborated previous studies, while others proved to be informative and raised the need for further chemosystematic studies. This provides the impetus for continuing to develop this method as a contribution to red algal systematics.