Diversity, taxonomy and host preference of leaf litter inhabiting microfungi in Doi Tung, Chiang Rai Province, Thailand

Abstract

Leaf litter is an essential functional aspect of forest ecosystems, acting as a source of organic matter, a protective layer in forest soils, and a nurturing habitat for micro- and macro-organisms. Through their successional occurrence, litter-inhabiting microfungi play a key role in litter decomposition and nutrient recycling. Despite their importance in terrestrial ecosystems and their abundance and diversity, information on the taxonomy, diversity, and host preference of these decomposer taxa is scarce. The present study aimed to elucidate saprobic leaf-litter fungal diversity in six phylogenetically related host species in Doi Tung, Chiang Rai province, Thailand, using morphological characters and multi-locus phylogeny. Tree species are Dipterocarpus alatus (Dipterocarpaceae), Nayariophyton zizyphifolium and Microcos paniculata (Malvaceae), Afzelia xylocarpa, Dalbergia cana, and Dalbergia cultrata (Fabaceae), located in Doi Tung, Chiang Rai province. We hypothesized that host species phylogeny significantly influences the diversity of fungal communities, and that each community is unique across phylogenetically distantly related host species. For each host species, three replicates were assigned. Fallen senescent leaves were randomly collected beneath the canopy of each host species were taken back to the laboratory in separate paper bags and observed for ix the saprobic fungi associated with each host. Moisture chambers were established for dry litter samples to favour the emergence of saprobic fungal taxa. Samples were observed for visible fruiting structures. For ascomycetes freehand sectioning, hyphomycetes specimens were directly picked for documenting morphological characters. A light microscope, coupled with Nikon DS-U2 and a Cannon 750D camera, was used to capture digital images. The single-spore-isolation method was used, to obtain pure cultures. Molecular sequence data were obtained through DNA extraction, polymerase chain reaction, agarose gel electrophoresis and sequencing. Sequences were analyzed, and phylogenetic trees were developed using maximum likelihood, maximum parsimony and Bayesian inference. The study generated evidence of multiple levels of diversity and host preference of leaf litter fungi. Results revealed one novel family, two novel genera and 16 new species generating evidence for multiple levels of diversity and host preference of leaf litter fungi. Most reported taxa belonged to the Dothideomycetes and Sordariomycetes, distributed among two classes, 25 families and 34 genera. Moreover, the study generated sexual asexual connections for Allophoma tropica and Diplodia guttulata providing the complete life cycle of these species. Most saprobes indicated host exclusivity and lower overlap between hosts. Higher levels of host phylogeny as family levels indicated to harbour a greater number of unique saprobic taxa rather than lower levels of host phylogeny as host species or genus levels. Moreover, the saprobic fungal community was influenced by the seasonal effect dominant during the collecting period. A core group of fungi could be identified as “generalists” observed in all the host species. The study highlights the diversity of saprobes dwelling inside the leaf litter of forest ecosystems and reveals their high degree of host specificity.