Species delimitation in the cyanolichen genus Rostania
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(2020) 20:115
RESEARCH ARTICLE
Open Access
Species delimitation in the cyanolichen genus Rostania Alica Košuthová1* , Johannes Bergsten2, Martin Westberg3 and Mats Wedin1
Abstract Background: In this study, we investigate species limits in the cyanobacterial lichen genus Rostania (Collemataceae, Peltigerales, Lecanoromycetes). Four molecular markers (mtSSU rDNA, β-tubulin, MCM7, RPB2) were sequenced and analysed with two coalescent-based species delimitation methods: the Generalized Mixed Yule Coalescent model (GMYC) and a Bayesian species delimitation method (BPP) using a multispecies coalescence model (MSC), the latter with or without an a priori defined guide tree. Results: Species delimitation analyses indicate the presence of eight strongly supported candidate species. Conclusive correlation between morphological/ecological characters and genetic delimitation could be found for six of these. Of the two additional candidate species, one is represented by a single sterile specimen and the other currently lacks morphological or ecological supporting evidence. Conclusions: We conclude that Rostania includes a minimum of six species: R. ceranisca, R. multipunctata, R. occultata 1, R. occultata 2, R. occultata 3, and R. occultata 4,5,6. Three distinct Nostoc morphotypes occur in Rostania, and there is substantial correlation between these morphotypes and Rostania thallus morphology. Keywords: Biodiversity, Fungi, Integrative taxonomy, Lichens, Phylogeny, Symbiosis, Systematics
Background Species delimitation as a topic has experienced a renaissance since the turn of the millennium [1]. Largely driven by the increasing use of molecular data in both phylogenetics and population genetics, the two historically parallel research fields now contribute different methodological and conceptual aspects to the interface where they meet in species delimitation and population divergence research [2]. However, while the genomic era offers ever increasing power to detect small differences between populations it is in no means the magic bullet to the problem of species delimitation [3, 4]. As an illustration, even with genomic data at hand, researchers still disagree about how many species of giraffes, orangutans or Darwin ground-finches exist [5, 6]. Recent appeals * Correspondence: [email protected] 1 Department of Botany, Swedish Museum of Natural History, P.O. Box 50007, SE-104 05 Stockholm, Sweden Full list of author information is available at the end of the article
discourage relying on genomic data alone for species delimitation and plea for an integrative approach including information on phenotypic and ecological variation [3, 6], in essence the concept of integrative taxonomy [7, 8]. Although not solving all problems with species delimitation, new molecular technologies have boosted the discovery of undescribed diversity in the lichen symbiosis. Until relatively recently, lichens have been viewed as a symbiosis between a single fungus (the mycobiont) and one or two photosynthesizing symbionts (the photobionts
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