Two new species of dictyostelid cellular slime molds in high-elevation habitats on the Qinghai-Tibet Plateau, China.

Dictyostelid cellular slime molds (dictyostelids) are key components of soil microbes. The Qinghai-Tibet Plateau is characterized by unique and important forest types because of the considerable range in elevation which exists. During the period of 2012, 2013 and 2016, 12 species of dictyostelids were yielded from samples collected in this region, including two new species and three new records for China. Six other species were new records for this region. Ontogeny, morphology, ultrastructure and systematic molecular analyses (SSU & ITS) of D. minimum and D. multiforme confirm that they are Goup 4 new species. The ornamentation of the surface of dictyostelids' spores is the first time to be observed until now. In the SSU phylogenetic tree generated in the present study, Synstelium, not assigned to order and family before, was assigned to the clade Acytosteliaceae in the Acytosteliales firstly. To our knowledge, the study reported herein is the first investigation of dictyostelid biodiversity carried out at elevations above 2000 m. Sorocarp size, sorus size, spore length, ratio of sorus and sorophore, and ratio of sorus and spore size were positively correlated with increasing elevation and no linear correlated with forest type, according to the results of linear regression analysis.