NTF distribution: watersheds vs grids
Of the 19 rare species with non-single site distributions within grids
or watersheds, 63.16% were distributed in the same or adjacent grid,
and 84.21% were distributed in the same or adjacent watershed. With the
exception of Drechslerella dactyloides , 8 of the 9 rare species
that only appeared in 2 or 3 sites were distributed in the same or
adjacent watershed (Figure 7).
At genetic level, the phylogenetic tree revealed that the
widespread species A.
oligospora was divided into 5 large clades. When grid was used as the
unit of analysis, no clear distribution pattern of these clades was
detected. When watershed was used as the unit of analysis, the
distribution of these clades was consistent with the natural watershed
divisions in Yunnan Province, except for Irrawaddy River, which has no
corresponding clade. The strains within the other clades were
distributed within their corresponding watersheds. The
64.70%,60.71%,80.00%,63.89% and 61.11% of the strains from clade
1 to clade 5 were correspondingly distributed in the Yangtze River, Red
River, Pearl River, Mekong, and Salween-Irrawaddy watersheds
respectively (Figure 8).
Based on our phylogenetic tree, the spatial distribution A.
oligospora was machine learned using the randomly generated Voronoi
polygons and the watersheds. We found that
the 45 maps generated using polygons
all had lower accuracy than the maps watersheds generated (Table S4). On
average, the accuracy of the polygons was low (mean: 36%, median:
38%), with all but one prediction falling below 50%. By assigning the
clades according to the watershedes, 68.8% of clades were classified
correctly (Figures S2, panel a). Watershed explained nearly 70 % ofA. oligospora distribution in Yunnan. None of the additional
climate, topographic, soil and vegetation variables significantly
improved the model (Figure S3,Table S5).
We were better able to capture the distribution pattern of NTF when
using watershed as the unit of analysis compared with grid (Figure 9).
Only 17 intersections of were found when we constructed upset plots
using watershed units. We found 19 species distributed in only one
watershed unit, and that 76.2% of all species were distributed in the
adjacent watersheds. There was a large gap between the dataset (variance
was 7.89, and mean value was 2.53). Despite finding 22 combinations when
constructing the integrative diagrams by grid, only 11 species were
distributed in only one grid and 55.0% of all species were distributed
in adjacent grids. There was a small fluctuation between the dataset
(variance was 5.04, and mean value was 1.77). Ultimately, using
watershed units led to a higher observation of endemic species, more
species distributed within adjacent or similar units, and a more varied
species composition, compared with using grid units.