Protist, Vol. 167, 148–173, April 2016 http://www.elsevier.de/protis Published online date 18 February 2016 ORIGINAL PAPER Phylogenetic Relationships and Biogeography of the Diatom Genus Mastogloia (Bacillariophyceae): Revision of the Section Ellipticae Including the Description of New Taxa Chiara Pennesi a,1 , Michel Poulin b , and Cecilia Totti a a Department of Life and Environmental Sciences, Laboratory of Marine Botany, Polytechnic University of Marche, via Brecce Bianche, 60131 Ancona, Italy b Research and Collections Division, Canadian Museum of Nature, PO Box 3443, Station D, Ottawa, ON KIP 6P4, Canada Submitted August 3, 2015; Accepted February 8, 2016 Monitoring Editor: W.H.C.F. Kooistra Benthic diatoms represent an important component of aquatic ecosystems, both for their contribu- tion to primary production and their role in the marine food web. Mastogloia is a large, mostly marine diatom genus occurring in microphytobenthic communities of temperate to tropical coastal regions. In this study, the phylogenetic relationships, based on cladistic methodologies using morphological features, among all taxa belonging to the genus Mastogloia section Ellipticae (i.e., 33 taxa) were investi- gated using the parsimony method. The character states that describe variations of central area, raphe, areola vela and partectal position have a tendency to be very homologous and useful in recovering phy- logenies. The typical character states of this section, such as rounded apices represents an ancestral homology. The phylogenetic hypothesis supports the probable monophyletic origin of the section Ellip- ticae (synapomorphy). Moreover, we completed the taxonomical review of the section Ellipticae, with the description of seven species, M. cocconeiformis, M. cribrosa, M. fimbriata, M. ovata, M. pseudolate- costata, and of two species new to science, M. rosalbae and M. aegyptiaca. Finally, this study provides historical and new information on the geographical distribution of Mastogloia species. © 2016 Elsevier GmbH. All rights reserved. Key words: Cladistic analysis; morphological features; Mastogloia; microphytobenthos; phylogeny; section Ellipticae. Introduction Mastogloia Thwaites ex W. Smith (1856) is a large, mostly marine diatom genus occurring in 1 Corresponding author; fax +390712204650 e-mail c.pennesi@univpm.it (C. Pennesi). coastal benthic environments of temperate to tropical regions (Hustedt 1933; Novarino 1989; VanLandingham 1971) and together with other biraphid (i.e., Diploneis Ehrenberg ex Cleve, Amphora Ehrenberg ex Kützing) and monoraphid (i.e., Cocconeis Ehrenberg, Achnanthes Bory de Saint-Vincent) genera, is highly diversified and http://dx.doi.org/10.1016/j.protis.2016.02.003 1434-4610/© 2016 Elsevier GmbH. All rights reserved.