Аннотация
This study presents a comparative analysis of morphological characters of nivicolous myxomycetes of the genus Physarum Pers. recorded in the Katon-Karagay and Ile-Alatau State National Nature Parks. The aim was to identify diagnostically significant features allowing the delimitation of nivicolous taxa under conditions of high morphological similarity and ongoing taxonomic revision of the family. Material was collected in spring 2025 during active snowmelt in high-mountain regions of Eastern and Southeastern Kazakhstan at elevations of 1570–3180 m a.s.l. Morphological examination of 56 specimens was conducted using light microscopy, focusing on characters of sporocarps, peridium, capillitium, columella, and spores. Four nivicolous taxa were identified: Badhamia albescens (Ellis ex T. Macbr.) J.M. García-Martín, J.C. Zamora & Lado, Nannengaella alpestris (Mitchel, S.W. Chapm. & M.L. Farr) J.M. García-Martín, J.C. Zamora & Lado, Physarum nivale (Meyl.) Mar. Mey. & Poulain, and Physarum vernum Sommerf. The most abundant species was Ph. vernum (45 specimens), while N. alpestris, Ph. nivale, and B. albescens were represented by 6, 4, and 1 specimens, respectively. The most informative diagnostic characters were the type and shape of fruiting bodies, presence of a stalk, degree and pattern of calcification of the peridium and capillitium, presence and morphology of the columella, and spore size and ornamentation. Specimens of N. alpestris, Ph. nivale, and Ph. vernum generally correspond to their protologues, whereas some Kazakh specimens of B. albescens show notable differences, suggesting the possible presence of closely related, yet undescribed taxa in the region. The results confirm the high diagnostic value of morphological characters for nivicolous Physarum spp. and highlight the perspectives of integrated morphological and molecular studies in Kazakhstan.