Evaluating community-environment relationships along fine to broad taxonomic resolutions reveals evolutionary forces underlying community assembly
1Institute of Oceanography, National Taiwan University, 2Ocean Networks Canada, University of Victoria, 3Research Center for Environmental Changes, Academia Sinica, 4Institute of Marine Environment and Ecology, NTOU, 5Center of Excellence for the Oceans, NTOU
We propose a method for linking evolutionary process to community assembly by quantifying the strength of community-environment relationships hierarchically along taxonomic ranks. This approach explores the potential role of phylogenetic conservatism on habitat preferences: wherein, phylogenetically related taxa are expected to exhibit similar responses to environmental filtering if a niche is conserved over evolutionary time. Thus, the strength of community-environment relationships should not deteriorate with broadly-resolved taxonomic data. It therefore follows that broader taxonomic classification would even yield stronger associations with environmental factors by balancing potential spatiotemporal randomness in occurrences and abundances of finely-resolved taxa. In contrast, weaker community-environment relationships should be expected with broadening taxonomic resolution if niche is not phylogenetically conserved, since broadly-resolved taxa would combine finer taxa with distinct environmental responses. Here, we quantified the strength of community-environment relationships at fine to broad taxonomic resolutions using distance-based redundancy analysis, focusing on bacterial community composition (based on 454 pyrosequencing data of the 16S rRNA gene) of oceanic and soil samples. We found that among 4 cases, the amount of variation in community composition explained by environmental factors increased or remained constant with broadening taxonomic resolution from species- to order- or even phylum-level. This finding supports the hypothesis of phylogenetic conservatism in bacterial lineages and indicates that broadening taxonomic resolution may strengthen niche-related signals by removing potential uncertainty in quantifying the spatiotemporal distribution of finely-resolved taxa. Our results reinforce the current notion of ecological coherence in deep bacterial branches, emphasizing the role of niche conservatism in bacterial community assembly.
keywords:bacterial community composition,community-environment relationship,ecological coherence,phylogenetic conservatism,taxonomic resolution