3D DIGITIZATION OF GRASS SILICA SHORT CELL PHYTOLITHS (GSSCP’S): A DIGITAL REFERENCE COLLECTION TO IMPROVE THEIR UTILITY FOR THE STUDY OF GRASSES AND GRASSLAND EVOLUTION

The use of phytoliths represents a promising advancement in the study of grass and grassland evolution. Grass silica short cell phytoliths (GSSCP’s) have diagnostic shapes which when properly assigned to specific clades can provide important information about the presence and abundance of grass lineages in place and time. Fossil grass phytolith assemblages as old as Late Cretaceous have been described providing new evidence for the age and diversification of the Poaceae, the timing, tempo and causes of grassland ecosystem expansion and the domestication history of our most important crops. However, the placement of ancient phytoliths into extant clades has been met with skepticism because a family-wide and statistically-robust analysis of 3D phytolith shape is not yet available. To address this problem, we are using confocal microscopy to develop a 3D digital reference collection of GSSCP’s from extant taxa across the Poaceae. Currently 200 species representing all 80 subtribes are being digitized. The resulting 3D surface representations provide a high degree of shape detail and are suitable for geometric morphometrics, virtual animations and 3D printing. The data will ultimately facilitate robust statistical analyses using machine learning algorithms and quantifiable placement of fossil phytolith taxa within the grass family. Our methodologies and initial results will be presented.