Description, culture and phylogenetic position of a new xerotolerant species of Physarum

Abstract

A new widespread myxomycete species, Physarum pseudonotabile, inhabiting the arid regions of the Eurasia, South and North America is described and illustrated. Tentatively assigned to Ph. notabile T. Macbr., a phylogeny based on the small ribosomal subunit (SSU) and elongation factor 1 alpha (EF1a) genes placed the new species in a clade far from Ph. notabile. Ph. pseudonotabile was found to be frequent in surveys based on the moist chamber culture technique with samples of litter, bark and herbivore dung collected in dry steppe and deserts of the Caspian lowland (Russia), Kazakhstan, Mongolia, China, Spain, Argentina and USA. The main morphological difference between Ph. pseudonotabile and Ph. notabile lies in spore ornamentation. Spores of the former species display irregularly distributed verrucae, whereas the latter species possesses spores with dense and regularly arranged spinulae. In addition, the ecological preferences of the two species differ. Ph. pseudonotabile inhabits the bark of living plants and ground litter in arid regions, whereas Ph. notabile is found on coarse woody debris in boreal and temperate forests. Although the new species appears to be closest to Ph. notabile morphologically, the phylogenetic analysis reveals Ph. pusillum and Ph. nivale as the closest relatives. In addition, the molecular investigations revealed a considerable amount of hidden diversity within species of Physarum with gray lime flakes. Currently we have only sufficient material to assess the morphological variation of Ph. pseudonotabile but expect that more taxa within this clade may emerge within studies combining morphological and molecular analyses.

• desert
• elongation factor alpha gene
• Myxogastria
• phylogeny
• spore-to-spore culture
• steppe
• taxonomy
• 18S rRNA

Acknowledgments

We gratefully acknowledge the technical support (SEM) provided by Ludmila A. Kartzeva. St Petersburg (Komarov Botanical Institute RAS) and A. Klahr (Greifswald University). We also thank Dr Adam Rollins (Biology Department. Lincoln Memorial University, USA), Dr Steve Stephenson (University of Arkansas), Dr G. Adamonyte (Institute of Botany, Nature Research Centre of Lithuania) and Dr A.V. Vlasenko (Central Siberian Botanical Garden, Russia) for assistance with specimens examined in the present study. We thank D.W. Mitchell for comments and linguistic help with the manuscript. Both field and molecular work was supported by grants from the Russian Foundation for Basic Research ( RFBR 10–04–00536a, 12-04-33018 mol_a_ved) by a grant from the Ministry of Education and Science of the Russian Federation (contract FNCP N 16.518.11.7071) and by a grant ( SCHN 1080/2–1) from the Deutsche Forschungsgemeinschaft.