Hidden diversity: multiple Arctic and Antarctic lineages in the cosmopolitan diatom Pinnularia borealis

• Main Authors: Pinseel, Eveline, Souffreau, Caroline, Vanormelingen, Pieter, Verleyen, Elie, Sabbe, Koen, Van de Vijver, Bart, Vyverman, Wim
• Format: Conference Object
• Language: English
• Published: 2015
• Subjects: Biology and Life Sciences; Bacillariophyta; Pinnularia borealis; Biogeography; Molecular Phylogeny; Polar Regions; Arctic; Antarctic; Canada; Livingston Island; Vega Island; Amsterdam Island; Antarc*; Marion Island; Spitsbergen
• Online Access: https://biblio.ugent.be/publication/7156765; http://hdl.handle.net/1854/LU-7156765

Pinnularia borealis Ehrenb. is a common diatom (Bacillariophyta) found on all continents. Although it has been observed in Antarctic waters with low nutrient and mineral content, P. borealis is mainly confined to (semi)terrestrial habitats such as seepages, moss vegetation and moist to dry soils. In the past, a large number of morphological forms have been described as subspecies, varieties or formas, but many of these show considerable morphological overlap resulting in an uncertain taxonomic status. Recently, detailed morphological analysis of several forms occuring in Amsterdam Island (sub-Antarctic) and Livingston Island (Maritime Antarctic) resulted in the description of inter alia P. sylviae Van de Vijver and P. quesadae Van de Vijver & Zidarova as species new to science. In parallel, a molecular phylogenetic approach was taken to tackle the species diversity, evolutionary history and biogeography of this enigmatic diatom. During field campaigns on various localities, including alpine, Arctic and Antarctic regions, samples were taken from soils, moss, seepages and the littoral zones of freshwater ponds and lakes. When P. borealis was present, cells were isolated, brought into culture and harvested for DNA and morphology analysis. In a first effort, samples were collected from Schirmacher Oasis (Continental Antarctic), Canada, Chile, Mongolia, Czech Republic, France and Belgium. Molecular phylogenies based on the plastid gene rbcL and the nuclear LSU rDNA revealed the presence of 8 lineages in P. borealis, including a distinct continental Antarctic lineage (Souffreau et al. 2013). A molecular clock estimates the origin of P. borealis at 30-47 million years ago and the age of the continental Antarctic lineage at 8 million years. Since then, the addition of 31 strains from Marion Island (sub-Antarctic), Vega Island (Maritime Antarctic), Spitsbergen (High Arctic) and Belgium resulted in the discovery of no less than 8 additional lineages and the co-existence of multiple lineages within a single region. ...