title: A MOLECULAR SYSTEMATIC APPROACH TO EXPLORE DIVERSITY WITHIN THE SELLAPHORA PUPULA SPECIES COMPLEX (BACILLARIOPHYTA)(1).
abstract: The common and cosmopolitan freshwater benthic diatom Sellaphora pupula (Kütz.) Mereschk. is a model system for studying the nature of species in microalgae; the biological significance of morphological variation in this species complex has been widely demonstrated. The aim of this study was to establish a two-gene phylogeny (18S rDNA and rbcL) for 23 Sellaphora taxa, including 19 S. pupula aggregate (agg.) demes or species, S. bacillum (Ehrenb.) D. G. Mann, and S. laevissima (Kütz.) D. G. Mann. A range of analyses on separate and combined data sets indicated that Sellaphora is a monophyletic group containing four major clades. Of the traditionally recognized species, S. bacillum and S. laevissima are natural groups, but S. pupula is paraphyletic or polyphyletic because S. bacillum groups with S. pupula"small lanceolate" and S. lanceolata. Thickened bars at the poles of valves within the core "pupula-bacillum" group may be a morphological synapomorphy; the fossil record suggests that this group is at least 12 million years old. Otherwise, there was no clear pattern in the distribution of different morphologies among the major clades; each clade was also heterogeneous with respect to mating system. More intensive and extensive sampling will doubtless uncover even greater diversity; the challenge lies in its interpretation. Our results demonstrate the limitations of paleoecological, ecological, and biogeographical research based on morphospecies.
authors.affiliation: Royal Botanic Garden Edinburgh, 20A Inverleith Row, Edinburgh EH3 5LR, UKLaboratory of Protistology and Aquatic Ecology, Department of Biology, Ghent University, Krijgslaan 281-S8, B-9000 Ghent, BelgiumRoyal Botanic Garden Edinburgh, 20A Inverleith Row, Edinburgh EH3 5LR, UK.
authors.forename: Katharine M
authors.initials: KM
authors.lastname: Evans
authors.affiliation: Royal Botanic Garden Edinburgh, 20A Inverleith Row, Edinburgh EH3 5LR, UKLaboratory of Protistology and Aquatic Ecology, Department of Biology, Ghent University, Krijgslaan 281-S8, B-9000 Ghent, BelgiumRoyal Botanic Garden Edinburgh, 20A Inverleith Row, Edinburgh EH3 5LR, UK.
authors.forename: Alexandra H
authors.initials: AH
authors.lastname: Wortley
authors.affiliation: Royal Botanic Garden Edinburgh, 20A Inverleith Row, Edinburgh EH3 5LR, UKLaboratory of Protistology and Aquatic Ecology, Department of Biology, Ghent University, Krijgslaan 281-S8, B-9000 Ghent, BelgiumRoyal Botanic Garden Edinburgh, 20A Inverleith Row, Edinburgh EH3 5LR, UK.
authors.forename: Gillian E
authors.initials: GE
authors.lastname: Simpson
authors.affiliation: Royal Botanic Garden Edinburgh, 20A Inverleith Row, Edinburgh EH3 5LR, UKLaboratory of Protistology and Aquatic Ecology, Department of Biology, Ghent University, Krijgslaan 281-S8, B-9000 Ghent, BelgiumRoyal Botanic Garden Edinburgh, 20A Inverleith Row, Edinburgh EH3 5LR, UK.
authors.forename: Victor A
authors.initials: VA
authors.lastname: Chepurnov
authors.affiliation: Royal Botanic Garden Edinburgh, 20A Inverleith Row, Edinburgh EH3 5LR, UKLaboratory of Protistology and Aquatic Ecology, Department of Biology, Ghent University, Krijgslaan 281-S8, B-9000 Ghent, BelgiumRoyal Botanic Garden Edinburgh, 20A Inverleith Row, Edinburgh EH3 5LR, UK.
authors.forename: David G
authors.initials: DG
authors.lastname: Mann
keywords: 18S rDNA; Bacillariophyta; Sellaphora pupula; biodiversity; biogeography; cryptic species; diatom; morphospecies; phylogeny; rbcL