Phylogenetic, ecological and intraindividual variability patterns in grass phytolith shape

Abstract

O_LIGrass silica short cell (GSSC) phytoliths appear to be the most reliable source of fossil evidence for tracking the evolutionary history and paleoecology of grasses. In recent years, modern techniques have been used to quantitatively assess phytolith shape variation. This progress has widened opportunities with respect to the classification of grass fossil phytoliths. However, phylogenetic, ecological and intraindividual variability patterns in phytolith shape remain largely unexplored. C_LIO_LIThe full range of intraindividual phytolith shape variation (3650 2D outlines) from 73 extant grass species, 48 genera, 18 tribes, and 8 subfamilies (with special attention paid to Pooideae) was analysed using the geometric morphometric analysis based on the semilandmarks spanning phytolith outlines. C_LIO_LIAlthough we showed that 2D phytolith shape is mainly driven by deep-time diversification of grass subfamilies, a closer look uncovered distinct phytolith shape variation in early-diverging lineages of Pooideae. C_LIO_LIThe phylogenetic pattern in phytolith shape was successfully revealed by applying geometric morphometrics to 2D phytolith shape outlines. This finding strengthens the potential of phytoliths to track the evolutionary history and paleoecology of grasses. Moreover, geometric morphometrics of 2D phytolith shape proved to be an excellent tool for analysis requiring large sums of phytolith outlines, making it useful for quantitative palaeoecological reconstruction. C_LI