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(Myxomycetes from caatinga and brejo de altitude areas in the semi-arid region of Pernambuco, Brazil). The Caatinga biome, situated in the Brazilian semi-arid region, is distributed among the territories of nine states, including Pernambuco. The objectives of this study were: (1) to understand the alpha and gamma diversity of the Caatinga myxobiota; and (2) to compare the composition of the myxobiota present in two areas of typical xerophilous vegetation situated in Serra Talhada (ST) and Mirandiba (M) municipalities with an enclave of rain forest situated in the municipality of Triunfo (T). Specimens were collected on woody debris (173), litter (26), debris of succulent plants (3), bark of a living tree (1) and dung (1). Hemitrichia calyculata was the most abundant species (60 records). Other common species were Arcyria cinerea (20), Ceratiomyxa fruticulosa (19), A. denudata (16) and H. serpula (13), which were collected during dry and humid periods. An annotated list is presented with records of 37 species from 17 genera, seven families and five orders. Myxomycetes assemblages differed from each other: CCM/ST = 0.25, CCM/T = 0.06, CCST/T = 0.39. The species/genus ratio was rather low in the caatinga and relatively high in the humid forest (S/G(M) = 1.0, S/G(ST) = 1.3, S/G(T) = 2.14). Specimen abundance and the total number of species (M = 4/4, ST = 26/12, T = 172/29) increased with increasing precipitation and altitude. Fuligo megaspora is reported for the first time for the Northeast Region and Didymium perforatum is a new record for Brazil.