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Taxonomy of three new Rhoicosphenia (Bacillariophyta) species from California, USA

Evan William Thomas, John Patrick Kociolek


Nearly two centuries of diatom floristic and ecological studies in North America have resulted in the recognition of relatively few Rhoicosphenia species. Three new species of Rhoicosphenia are described from water quality monitoring samples from streams across the state of California. Rhoicosphenia stoermeri is large, with a panduriform central area. Rhoicosphenia lowei is also large, but the valve is narrower than R. stoermeri, and its central area is smaller. Rhoicosphenia californica is narrow and linear and the most commonly encountered of the newly described species. Light and scanning electron microscope observations of these new species with comparisons to previously described taxa, coupled with ecological and distribution data from across the state, highlight the overlooked Rhoicosphenia diversity in North America. The ultimate goal of this work is to aid in refined taxonomic identifications within the genus with the possibility of increased resolution in ecological studies using diatoms.


Rhoicosphenia, Bacillariophyta, diatom, endemic, streams, pseudocryptic, dichotomous key



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ISSN 1179-3155 (print); ISSN 1179-3163 (online)

Published by Magnolia Press, Auckland, New Zealand