Type analysis of Achnanthidium minutissimum and A. catenatum and description of A. tropicocatenatum sp. nov. (Bacillariophyta), a common species in Brazilian reservoirs

• Published in: Plant ecology and evolution 2017-11, Vol.150 (3), p.313-330
• Main Authors: Marquardt, Gisele C., Costa, Lívia F., Bicudo, Denise C., de M. Bicudo, Carlos E., Blanco, Saúl, Wetzel, Carlos E., Ector, Luc
• Format: Article
• Language: English
• Subjects: Distribution; Ecological Optimum; Ecology; Geometric Morphometry; Morphology; New Species; Taxonomy
• ISSN: 2032-3913; 2032-3921
• DOI: 10.5091/plecevo.2017.1325

Background and aims - A commonly occurring Achnanthidium species has been observed in Brazilian reservoirs. The morphological features were described based on light and scanning electron microscope observations and it is described here as A. tropicocatenatum sp. nov.Methods - The new species was compared with the type material of morphologically similar taxa: Achnanthidium catenatum and A. minutissimum. Comparisons with the most related species based on literature were also provided. Traditional weighted-averaging approaches (WA) were applied to model ecological optima.Key results - Morphometric analysis of the valve shape supported the taxa separation; they can be easily differentiated by the morphological and ultrastructural features, including subcapitate to capitate apices, strongly radiate striae and a prominent axial area. This new species has been found in alkaline waters with low electrolyte content.Conclusions - Records of A. catenatum in Brazil are considered questionable because the species may have been confused with A. tropicocatenatum sp. nov.