Investigation of the type material of Microneis gracillima, Navicula pyrenaica, Achnanthes amphicephala, Achnanthes thienemannii and Achnanthidium rostropyrenaicum (Achnanthidiaceae, Bacillariophyta) and additional populations of the species

Abstract

The historic type material of <i>Microneis gracillima</i>, <i>Navicula pyrenaica</i>, <i>Achnanthes amphicephala</i>, <i>Achnanthes thienemannii</i> and <i>Achnanthidium</i> <i>rostropyrenaicum</i> was investigated together with additional European populations of these species using light and scanning electron microscopy. The morphology of the species was compared to similar taxa. <i>Achnanthes amphicephala</i> is transferred to the genus <i>Achnanthidium</i>. The species are distinguished from each other in the shape of their poles and in valve outline. There are currently very few photographic records of the species, but our results suggest that these species are typical in base-rich, oligotrophic waters, and might be important indicator species for these habitats.