Molecular and morphological diversity of Zygnema and Zygnemopsis (Zygnematophyceae, Streptophyta) from Svalbard (High Arctic)

• Published in: European journal of phycology 2018-10, Vol.53 (4), p.492-508
• Main Authors: Pichrtová, Martina, Holzinger, Andreas, Kulichová, Jana, Ryšánek, David, Šoljaková, Tereza, Trumhová, Kateřina, Nemcova, Yvonne
• Format: Article
• Language: English
• Subjects: Adaptation; Arctic; Arctic region; chloroplast shape; Chloroplasts; confocal laser scanning microscopy; Confocal microscopy; Conjugation; cryptic diversity; Cytology; Environmental conditions; environmental factors; Filaments; Genetic diversity; Genetic variation; genotype; Genotypes; Lasers; Meltwater; microalgae; Microscopy; molecular phylogeny; Morphology; New records; Norway; Phylogeny; Polar environments; rbcL; ribulose-bisphosphate carboxylase; Sexual reproduction; snowmelt; Svalbard; Taxonomy; Terrestrial environments; trophic relationships; Zygnema; Zygnemopsis; Zygospores
• ISSN: 0967-0262; 1469-4433; 1469-4433
• DOI: 10.1080/09670262.2018.1476920

Filamentous conjugating green microalgae (Zygnematophyceae, Streptophyta) belong to the most common primary producers in polar hydro-terrestrial environments such as meltwater streamlets and shallow pools. The mats formed by these organisms are mostly composed of sterile filaments with Zygnema morphology, but the extent of their diversity remains unknown. Traditional taxonomy of this group is based on reproductive morphology, but sexual reproduction (conjugation and formation of resistant zygospores) is very rare in extreme conditions. In the present study we gave the first record of zygospore formation in Svalbard field samples, and identified conjugating filaments as Zygnemopsis lamellata and Zygnema cf. calosporum. We applied molecular phylogeny to study genetic diversity of sterile Zygnema filaments from Svalbard in the High Arctic. Based on analysis of 143 rbcL sequences, we revealed a surprisingly high molecular diversity: 12 Arctic Zygnema genotypes and one Zygnemopsis genotype were found. In addition, we characterized individual Arctic genotypes based on cell width and chloroplast morphology using light and confocal laser scanning microscopy. Our findings highlight the importance of a molecular approach when working with sterile filamentous Zygnematophyceae, as hidden diversity might be very beneficial for adaptation to harsh environmental conditions, and experimental results could be misinterpreted when hidden diversity is neglected.