Morphometrics of Starch Granules from Sub-Saharan Plants and the Taxonomic Identification of Ancient Starch

Abstract

The assumption that taxonomy can be ascertained by starch granule shape and size has persisted unchallenged since the late nineteenth and early twentieth century biochemistry. More recent work has established that granule morphological affinity is scattered throughout phylogenetic branches, morphotype proportions vary within the genus, granules from closely related genera can differ dramatically in shape, and size variations do not reflect phylogenetic relationships. This situation is confounded by polymorphism at the species and tissue level, resulting in redundancy and multiplicity.This paper classifies morphological features of starch granules from 77 species, 31 families, and 22 orders across three African ecoregions. This is the largest starch reference collection published to date, rendering the dataset uniquely well suited to explore i) the diagnostic power of unique morphometric classifiers and their frequency, ii) morphotypes that cut across taxonomic boundaries, and iii) issues surrounding the minimum counts needed to accurately reflect granule polymorphism, variability, and identification.In a collection of 23,100 granules, taxonomic identification occurred very rarely. In the instances it did, it was at the species level, with no occurrences of a single morphotype or complement identifying all species within a family or genus. Some families cannot be uniquely identified, and morphometric types are shared despite taxonomic distance for three quarters of the taxa. However, this reference collection boasts 98 unique identifiers located in the Arecaceae, Convolvulaceae, Cyperaceae, Dioscoreaceae, Fabaceae, Musaceae, Pedaliaceae, Poaceae, and Zamiaceae.

Fingerprinting Starch Degradation Products: Chemical Species of Interest to Ancient Starch Research

“…We selected starch samples from a collection at the University of Calgary https://olduvaigorgesds.com/botanical-reference-collection/ on Africanist, ethnobotanical criteria. Sixteen taxa across phylogenetic orders (n=8) and genera (n=15), with varied crystallinity (Table 1: Type A = 5, B = 3, C = 8) and granule morphometry (Mercader et al 2018b). From this total, four non-African crops (potato, wheat, maize, and taro) were included because of their universal availability and well understood chemical and molecular structure (e.g.…”

Advances in Morphometrics in Archaeobotany

“…In most archaeological studies of starch, taxonomic identification is made by comparing the gross or general size, shape, and optical attributes of ancient granules with those of reference collections (Torrence 2006b;Ugent 2006), but a limited number have developed automated systems of identification (Torrence et al 2004;Wilson et al 2010;Aceituno and López-Sáez 2012;Coster and Field 2015;Arráiz et al 2016;Mercader et al 2018).…”

“…Arráiz et el. 2016and Mercader et al (2018) analysed starch grains produced by plants exploited by indigenous communities in Sub-Saharan Africa to evaluate morphometric variations among taxa and the reliability of large datasets; the latter work is the largest reference collection published to date, consisting of 23,100 starch granules from 77 species.…”

What does the quantitative morphological diversity of starch grains in terrestrial orchids indicate?

“…Definitions related to starch morphology concentrates on qualitative characteristics such as the shape of the starch grains (round, oval, semicircular, triangular, etc. ), whether they are simple or compound, the position of the hilum (centric or eccentric), whether the lamellae, extinction cross, pits, oblong central cavity, mesial longitudinal cleft, fissures are prominent or not (Brown & Louderback, 2020; Colussi et al, 2021; Mercader et al, 2018; Reichert, 1912). These studies are related to the descriptive features of the characters.…”