Discussion
Widespread species masked thebiogeographic patterns of
microbes
Nearly half of the reported NTF species (N = 44) in 3 genera were found
during this study. At the species level, the distribution pattern was
random and had no heterogeneous pattern. The number of common species
only accounted for less than 5% of the total species but contributed to
70% of the OF. When excluding the 4
widespread species, the pattern
tended to be non-random with a clear heterogenous pattern. If the
distribution of the species with high OF were gradually superimposed,
the patterns of NTF tended to be random. The results indicated that the
extreme high OF and wide distribution of the common species mask
microbial heterogeneous biogeographic patterns.
The 31 rare species were restricted to 0.44% ~ 9.21%
of the sampling sites. The genera Dactylella andDrechslerella were restricted in 7.02% and 7.89% of the
sampling sites respectively. Because the limited distribution and the
existence of endemic species were representative of the biogeographic
pattern in itself5, we concluded that NTF has
heterogeneous biogeographic patterns..Although the rare species were low
in abundance, they played a key role in understanding microbial
biogeographic patterns. A low sampling effort may have limited any
observations of these species. In this study, rare species (OF
< 1%) accounted for 70.45% of the 2,250 specimens collected
in Yunnan Province. Had the sampling effort been reduced by 10%, we
estimated that 29 of all species (93.54% of rare species) would have
been more difficult to observe. Studies that used metagenomics to
investigate microbial diversity patterns reported a sampling intensity
interval between 3~300 samples, with an average of 40
samples collected (summarised according to articles published in The
ISME Journal and Microbiome over the past five years). Sampling efforts
were subsequently reduced to same time and resources when using
metagenomic methods (Karimi et al ., 2018). With low sampling
efforts, many rare species would be ignored.