Abstract
BackgroudFoliicolous algae are a common occurrence in tropical forests. They are referable to a few simple morphotypes (unicellular, sarcinoid-like or filamentous), which makes their morphology of limited usefulness for taxonomic studies and species diversity assessments. The relationship between algal community and their host phyllosphere was not clear. In order to obtain a more accurate assessment, we used single molecule real-time sequencing of the 18S rDNA gene to characterize the eukaryotic algal community in an area of South-western China.ResultWe annotated 2922 OTUs belonging to five classes, Ulvophyceae, Trebouxiophyceae, Chlorophyceae, Dinophyceae and Eustigmatophyceae. Novel clades formed by large numbers sequences of green algae were detected in the order Trentepohliales (Ulvophyceae) and the Watanabea clade (Trebouxiophyceae), suggesting that these foliicolous communities may be substantially more diverse than so far appreciated and require further research. Species in Trentepohliales, Watanabea clade and Apatococcus clade were detected as the core members in the phyllosphere community studied. Communities from different host trees and sampling sites were not significantly different in terms of OTUs composition. However, the communities of Musa and Ravenala differed from other host plants significantly at the genus level, since they were dominated by Trebouxiophycean epiphytes.ConclusionThe cryptic diversity of eukaryotic algae especially Chlorophytes in tropical phyllosphere is very high. The community structure at species-level has no significant relationship either with host phyllosphere or locations. The core algal community in tropical phyllopshere is consisted of members from Trentepohliales, Watanabea clade and Apatococcus clade. Our study provided a large amount of novel 18S rDNA sequences that will be useful to unravel the cryptic diversity of phyllosphere eukaryotic algae and for comparisons with similar future studies on this type of communities.
Highlights
The phyllosphere comprises the aerial parts of plants and is mainly constituted by the leaves, which can be considered an ephemeral environment [1]
Our study provided a large amount of novel 18S rDNA sequences that will be useful to unravel the cryptic diversity of phyllosphere eukaryotic algae and for comparisons with similar future studies on this type of communities
Most coccoid green algae or SSU rDNA sequences retrieved from leaves are nested into trebouxiophycean clades corresponding to the genera Chlorella, Auxenchlorella, Myrmecia, Coccomyxa, Elliptochloris, Diplosphaera, Stichococcus, Prasiola, Trebouxia and Asterochloris [15, 23,24,25,26,27,28], whereas filamentous green algae belong to the genera Phycopeltis, Cephaleuros, Trentepohlia and Klebsormidium [9, 17, 29, 30]
Summary
The phyllosphere comprises the aerial parts of plants and is mainly constituted by the leaves, which can be considered an ephemeral environment [1]. Most studies on microbial life in the phyllosphere have focused on bacteria and fungi. The composition of their communities, their adaptions to the phyllosphere and. It has been shown that these epiphyllous forms represent a very heterogeneous and evolutionarily diverse assemblage, which mainly consist of cyanobacteria and green microalgae such as coccoid trebouxiophycean algae and branched trentepohliacean algae [9, 10]. Cultivation-independent studies reported that eukaryotic algae are abundant on rainforest leaves, and the available knowledge about these forms suggests that there may be a huge number of unknown species [16,17,18,19]. The Xanthophyceaen genus Heterococcus was reported as phycobiont in lichens [26]
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