Phylogenetic, ecological and intraindividual variability patterns in grass phytolith shape

Area of Science:

• Paleobotany and Evolutionary Biology
• Plant Morphology and Anatomy

Background:

• Grass silica short cell (GSSC) phytoliths are key fossil evidence for grass evolution and paleoecology.
• Quantitative analysis of phytolith shape variation offers new classification opportunities.
• Phylogenetic, ecological, and intraindividual phytolith shape variability patterns require further exploration.

Purpose of the Study:

• To analyze the full range of intraindividual phytolith shape variation in extant grasses.
• To explore phylogenetic patterns in phytolith shape using geometric morphometrics.
• To assess the utility of 2-D phytolith shape analysis for paleoecological reconstruction.

Main Methods:

• Geometric morphometric analysis of 3650 two-dimensional (2-D) phytolith outlines.
• Analysis encompassed 73 grass species, 48 genera, 18 tribes, and eight subfamilies, with a focus on Pooideae.
• Semi-landmarks were used to span phytolith outlines for shape analysis.

Main Results:

• Two-dimensional (2-D) phytolith shape is primarily influenced by deep-time diversification of grass subfamilies.
• Distinct phytolith shape variations were observed in early-diverging Pooideae lineages (Meliceae, Stipeae).
• Significant variation in intraindividual phytolith shape exists across species, creating a notable phylogenetic pattern.

Conclusions:

• Geometric morphometrics successfully revealed phylogenetic patterns in 2-D phytolith shape outlines.
• Phytoliths, analyzed via geometric morphometrics, show strong potential for tracking grass evolutionary history and paleoecology.
• This method is valuable for quantitative paleoecological reconstruction, especially with large phytolith datasets.