title: Dynamics of yeast populations recovered from decaying leaves in a nonpolluted stream: a 2-year study on the effects of leaf litter type and decomposition time.
abstract: Here we report on the results of a survey of the yeast populations occurring on submerged leaves (alder, eucalyptus and oak) in a natural mountain stream, during different phases of their decomposition and through two consecutive years. Leaf litter mass loss, total yeast counts, Shannon-Weiner index (H'), yeast community structure and physiologic abilities were analyzed to evaluate the dynamics of yeast communities during decay. Seventy-two yeast taxa were recorded, and in all litter types, species of basidiomycetous affinity predominated over ascomycetous ones. Discriminant analysis of presence/absence data (yeast species) showed significant differences both among substrate types (P<0.0026) and with decomposition time (P<0.0001). Carbon and nitrogen source utilization by yeast strains also varied with the substrate (P<0.0001) and decomposition time (P<0.0001). Further conclusions were that: (1) all litter types have in common ubiquitous yeast species, such as Cryptococcus albidus, Debaryomyces hansenii and Rhodotorula glutinis, among the common 20 yeast species; (2) only a few species were dominant, and most species were rare, being recorded once or twice throughout decomposition; and (3) the order of yeast appearance, and their substrate assimilation patterns, strongly suggest a succession phenomenon. Finally, explanations for the distribution patterns and variations in yeast communities are discussed.
authors.affiliation: Centro de Estudos Tecnológicos do Ambiente e da Vida, Departamento de Engenharia Biológica e Ambiental, Universidade de Trás-os-Montes e Alto Douro, Portugal. asampaio@utad.pt
authors.forename: Ana
authors.initials: A
authors.lastname: Sampaio
authors.forename: José Paulo
authors.initials: JP
authors.lastname: Sampaio
authors.forename: Cecília
authors.initials: C
authors.lastname: Leão
mesh_terms: D044822:Biodiversity; D017753:Ecosystem; D020387:Food Chain; D018515:Plant Leaves / Q000382:microbiology*; D011174:Portugal; D045483:Rivers / Q000382:microbiology*; D015003:Yeasts / Q000145:classification* / Q000254:growth & development / Q000378:metabolism