Diatoms of North AmericaDescription: The genus Neidium within the
order Naviculales, contains a large array of species that are never
really abundant, live in a wide range of autecological conditions from
alkaline to acidic, and are exclusively freshwater. The genus is easily
distinguished by valve morphology, chloroplast structure and
specifically the autapomorphic presence of renilimbia on the internal
valve. Taxonomically, the confusion in identifying species dates back to
C.G. Ehrenberg and P.T. Cleve with poor line drawing and weak
descriptions documenting some of the common American and European
species. Further, species show a wide range in grading morphological
forms, which has created additional confusion in the literature. With
access to the original Ehrenberg material and genetic analyses we have
been able to sort out many of the old problematic taxa and have a more
developed understanding of the phylogeny. At present there are greater
than 300 described species, varieties and forms, most requiring
re-examination and validation. Using morphology and genetics this
presentation will explore 20-30 of the more prominent Neidium
taxa with an emphasis on morphological relationships including
structural complexity of longitudinal canals and the valve wall. Some of
the taxa discussed will include N. affine, N. amphigomphus, N.
ampliatum, Neidium beatyi, N. boyeri, N. dilatatum, N.
distinctepunctatum, N. firma, N. fossum, N. hitchcockii, N. iridis, N. potapovae, and N. rudimentarum. The primary objectives of this talk will be to explore the wide morphological variability of valve forms within the genus Neidium. The
presentation will also introduce the utility of adding genetic analyses
to taxonomic studies, including a short presentation on an efficient
way to make micropipettes for single diatom cell isolations.
Target Audience: The
talk is aimed at anyone interested in diatom phylogeny and
classification.
