Quantitative comparison of taxa and taxon concepts in the diatom genus Fragilariopsis : a case study on using slide scanning, multiexpert image annotation, and image analysis in taxonomy 1

BESZTERI, BÁNK; ALLEN, CLAIRE; ALMANDOZ, GASTÓN O.; ARMAND, LEANNE; BARCENA, MARÍA ÁNGELES; CANTZLER, HANNELORE; CROSTA, XAVIER; ESPER, OLIVER; JORDAN, RICHARD W.; RIGUAL HERNÁNDEZ, ANDRÉS S.

JOURNAL OF PHYCOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2018

0022-3646

Semiautomated methods for microscopic imageacquisition, image analysis, and taxonomicidentification have repeatedly received attention indiatom analysis. Less well studied is the questionwhether and how such methods might prove usefulfor clarifying the delimitation of species that aredifficult to separate for human taxonomists. To try toanswer this question, three very similar Fragilariopsisspecies endemic to the Southern Ocean weretargeted in this study: F. obliquecostata, F. ritscheri,and F. sublinearis. A set of 501 extended focus depthspecimen images were obtained using a standardized,semiautomated microscopic procedure. Twelvediatomists independently identified these specimenimages in order to reconcile taxonomic opinions andagree upon a taxonomic gold standard. Using imageanalyses, we then extracted morphometric featuresrepresenting taxonomic characters of the target taxa.The discriminating ability of individual morphometricfeatures was tested visually and statistically,and multivariate classification experiments wereperformed to test the agreement of the quantitativelydefined taxa assignments with expert consensusopinion. Beyond an updated differential diagnosis ofthe studied taxa, our study also shows that automatedimaging and image analysis procedures for diatomsare coming close to reaching a broad applicability forroutine use.