NOVAIS, Maria Helena, Ingrid JÜTTNER, Lucien HOFFMANN, & Luc ECTOR 2015 (online Aug. 28) Morphological variability within the Achnanthidium minutissimum species complex (Bacillariophyta): comparison between the type material of Achnanthes minutissima and related taxa, and new freshwater Achnanthidium species from Portugal Phytotaxa 224(2): 101-139, 477 figs., 6 tables