# A Morphometric Analysis of Starch Granules from Two Dioscorea Species

## TL;DR

This study analyzes starch granules from two yam species to help archaeologists identify them in ancient tools, focusing on their cultural and nutritional importance in Tonga.

## Contribution

The study introduces two novel morphometric characteristics (eccentricity ratio and hilum angle) for distinguishing starch granules from two Dioscorea species.

## Key findings

- The two novel morphometric characteristics effectively distinguish D. alata and D. bulbifera starch granules.
- Approximately 300 granules per species were analyzed, providing a reliable dataset for archaeological identification.
- The findings increase confidence in assigning archaeological starch granules to specific Dioscorea species.

## Abstract

Dioscorea is a genus comprising over 600 species, many of which possess edible tubers that are commonly referred to as yams. While Dioscorea is a significant crop across the globe, it holds a unique cultural significance to the people of Tonga in western Polynesia. Presently, Dioscorea is known for its essential role in festivals and ceremonies, as well as for its nutritional contributions to Tongan diets. To understand and to assess the significance of Dioscorea in the distant past, however, archeologists rely on plant residues (e.g., starch granules) preserved on ancient tools. This study provides the necessary first step in archeological starch analysis by examining the granule morphometrics of two culturally significant Dioscorea species, D. alata and D. bulbifera from Tonga. Tubers from three individuals of each species were collected on the island of Vava’u and processed for starch granule extraction and analysis. Morphometric characteristics, including two novel that describe shape (eccentricity ratio and hilum angle), were measured on approximately 300 granules per species. When statistically compared, these novel characteristics allow D. alata and D. bulbifera to be readily distinguished from one another, and therefore increase confidence in assigning archeological granules to a specific taxon.