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Front. Earth Sci. | doi: 10.3389/feart.2018.00146

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

 Julio Mercader1*, Matthew Abtosway1, Robert Bird1, Mariam Bundala1, Siobhan Clarke1,  Jamie L. Inwood1, Makarius Itambu1, Fergus Larter1, Robert Patalano1,  Maria Soto1, Laura Tucker1 and Dale Walde1
  • 1University of Calgary, Canada

The assumption that taxonomy can be ascertained by starch granule shape and size has persisted 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.

Keywords: Starch granule Morphometry, Reference collection, Starch identification, Ancient starch research, Sub-Saharan Ethnobotany, Unique identifiers

Received: 26 Jun 2018; Accepted: 13 Sep 2018.

Edited by:

Steven L. Forman, Baylor University, United States

Reviewed by:

Donald M. Thieme, Valdosta State University, United States
Monica Tromp, Max-Planck-Institut für Menschheitsgeschichte, Germany  

Copyright: © 2018 Mercader, Abtosway, Bird, Bundala, Clarke, Inwood, Itambu, Larter, Patalano, Soto, Tucker and Walde. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Julio Mercader, University of Calgary, Calgary, Canada, julio.mercader@gmail.com