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.

Phylogeny of Physarida (Amoebozoa, Myxogastria) Based on the Small‐Subunit Ribosomal RNA Gene, Redefinition of Physarum pusillum s. str. and Reinstatement of P. gravidum Morgan

“…This sequence was later used to assign the name “ P. pusillum ” to the sequences – of the specimens LE255719 and LE255721 by Novozhilov et al. (). The tree published therein included only one sequence of Physarum in addition to the sequences obtained by the authors: thus, the grouping of the sequence with the sequences and was due to undersampling.…”

Biogeographical assessment of myxomycete assemblages from Neotropical and Asian Palaeotropical forests

“…Most of our knowledge about myxomycete assemblages has been derived from surveys which have recorded fructifications in the field or from moist chamber cultures (Stephenson et al ., ). In terms of biogeography, most studies have been carried out in temperate regions of the Northern Hemisphere, including alpine and subalpine mountains (Ronikier & Ronikier, ; Novozhilov et al ., ), tundra (Novozhilov et al ., ; Stephenson et al ., ), winter‐cold deserts (Schnittler & Novozhilov, ; Schnittler, ; Novozhilov & Schnittler, ) and temperate grasslands (Rollins & Stephenson, ). Only recently have other parts of the world, such as tropical zones, warm deserts or the Patagonian steppe been studied systematically (Estrada‐Torres et al ., ; Wrigley de Basanta et al ., ; Lado et al ., , , ).…”

“…Moreover, certain vegetation types contain species that are locally abundant but do not occur elsewhere. This is best documented for deserts; examples include Physarum pseudonotabile Novozh., Schnittler & Okun in Central Asia (Novozhilov & Schnittler, ; Novozhilov et al ., ), or Perichaena calongei Lado, D. Wrigley & Estrada, Didymium infundibuliforme D. Wrigley, Lado & Estrada and Physarum atacamense D. Wrigley, Lado & Estrada in South America (Lado et al ., ; Wrigley de Basanta et al ., , ; Araujo et al ., ). Whether this is due to the lack of data from many areas of the world or due to some morphologically recognizable myxomycete species occurring with a limited distribution is a question being debated.…”

“…Moreover, certain vegetation types contain species that are locally abundant but do not occur elsewhere. This is best documented for deserts; examples include Physarum pseudonotabile Novozh., Schnittler & Okun in Central Asia Novozhilov et al, 2013) Wrigley de Basanta et al, 2009Araujo et al, 2015). Whether this is due to the lack of data from many areas of the world or due to some morphologically recognizable myxomycete species occurring with a limited distribution is a question being debated.…”

A workflow for low-cost automated image analysis of myxomycete spore numbers, size and shape

“…Even more interesting, what is the genetic constitution of such spores? Are they multinucleated (as shown for myxomycetes, Novozhilov et al, 2013 ), or do they represent restitutional diploid nuclei after an aberrant meiosis? There is evidence that in myxomycetes, meiosis usually occurs after spore cleavage inside the young spores ( Clark & Haskins, 2013 ).…”