Vol.:(0123456789) 1 3 Polar Biology https://doi.org/10.1007/s00300-018-2308-3 ORIGINAL PAPER Genetic structure of Galdieria populations from Iceland Ayla Eren 1  · Manuela Iovinella 2  · Hwan Su Yoon 3  · Paola Cennamo 4  · Mario de Stefano 5  · Olga de Castro 6  · Claudia Ciniglia 5 Received: 21 May 2017 / Revised: 8 March 2018 / Accepted: 15 March 2018 © Springer-Verlag GmbH Germany, part of Springer Nature 2018 Abstract Galdieria is a photosynthetic unicellular protist, inhabiting thermoacidic environments around the world. The synchronicity of these thermoacidophilic algae with their extreme habitats makes them unable to thrive in diferent ecological conditions. The genetic structure of Galdieria populations has not yet been studied. In this report, the level of genetic diversity and struc- ture of fve Galdieria populations from Iceland were assessed through both random amplifed polymorphic DNA (RAPD) markers, and a partial calmodulin gene fragment (previously used to assess the population structure of these extremophilic algae). The level of population diferentiation from both the RAPD and CaM markers was estimated using PLP, percentage of polymorphic loci; H, the expected heterozygosity; I, Shannon’s information index, Ks, Kst. The migration ability of the Galdieria populations was suggested by the high level of genetic variations scored within each Galdieria population and by the small number of polymorphisms detected between the diferent Icelandic populations. The low genetic diversity between the two species was highlighted by RAPD and calmodulin markers, suggesting for the frst time an interspecifc genetic fow between species as strategy to evolve in stressful environments. Keywords CaM gene · Galdieria · Genetic structure · Microalgae · RAPD · Iceland · Rhodophyta Introduction The biodiversity of acidic and thermal environments has become increasingly interesting, as these environments were widespread during the early life of our planet, therefore the organisms isolated from these sites may be representative of archaic life forms. The Galdieria genus (Cyanidiophyceae, Rhodophyta) represents one of most ancient groups of algae (Yoon et al. 2004; Cennamo et al. 2012) which have a panmictic distribu- tion across most geothermal areas worldwide (Ciniglia et al. 2004, 2007; Toplin et al. 2008; Ciniglia et al. 2014). Their emerald colour characterizes the hydrothermal soils, where temperatures rise above 50 °C, and high sulphuric acid con- centrations greatly reduce the pH to values prohibitive for the majority of eukaryotic life forms (pH 0.5–3.0) (Brock 1978; Albertano et al. 2000; Pinto et al. 2003; Ciniglia et al.2004; Pinto et al. 2007; Cennamo et al. 2017). Galdie- ria spp. reproduction is exclusively asexual and neither gam- etes nor resting spores have ever been observed during their life cycle (Pinto et al. 2003; Ciniglia et al. 2004). The high level of rbcL gene sequence divergence within this genus has contributed to the taxonomy of Galdieria (Cozzolino et al. 2000; Pinto et al. 2003; Ciniglia et al. 2004), the main lineages identifed so far are: G. phlegrea (ex Galdieria-B; Pinto et al. 2007) comprising strains col- lected in thermoacidic Italian sites; G. sulphuraria, a group that is geographically dispersed worldwide, including G. Ayla Eren and Manuela Iovinella have equally contributed to this paper * Claudia Ciniglia claudia.ciniglia@unicampania.it 1 Sakarya University, Sakarya, Turkey 2 Department of Biology, University of York, Wentworth Way, York, UK 3 Department of Biological Sciences, Sungkyunkwan University, Seoul, South Korea 4 Faculty of Letters, University of Naples Suor Orsola Benincasa, Naples, Italy 5 Department of Environmental, Biological and Pharmaceutical Science and Technology, University of Campania “L. Vanvitelli”, Caserta, Italy 6 Department of Biology, University of Federico II, Naples, Italy