Relationship between inflow intensity and species richness
The species richness was positively correlated with inflow intensity
along elevation in Lebu Valley (R ²=0.31, P <0.01; Figure
4a). Species richness along elevation in Lebu Valley showed a
hump-shaped pattern (Figure 4b)—better fitted by a
cubic equation of elevation than a
linear equation and quadratic
equation (the AICc value was 197.55
for the linear equation, 157.44 for the quadratic equation, and 139.93
for the cubic equation). The species richness “hump” occurred from
2,750 to 3,650 m a.s.l. Species from both ends of the elevational
gradient in Lebu Valley would contribute to the observed hump-shaped
species richness pattern.
To test whether the proximity of the range margins of potentially
interacting species from both sides of the “hump” of species richness
was identical, we compared the inflow intensity between the low
elevational bands (band No. 1-13, from 2,350 to 3,650 m a.s.l.) and high
elevational bands (band No. 14-26, from 3,650 to 4,950 m a.s.l.). We
found that the mean of the inflow intensity of the low elevational bands
(Means=842.85, Standard Deviation=94.75) was higher than the mean of the
inflow intensity of the high elevational bands (Means=709.46, Standard
Deviation=419.32) (t-test: t =1.12, P <0.01). Moreover, we
also compared the “effective” species richness (defined as the number
of species appearing in the “hump”) of the low abundance center
species (n=83) and high abundance center species (n=40) to test the
differences in inflow intensity. We found the elevational range of 77
species (93%) in low abundance center species overlapped with the
“richness hump”, and the elevational range of 9 species (23%) of high
abundance center species overlapped with the “richness hump” (Figure
2).