Fig 1.
Examples of HOF models (types II-VII) showing the responses of species along a pH gradient.
A species with model type I shows no response along the gradient (b shows Chrysosplenium alternifolium). Thick vertical solid lines describe the position of the optima, thin vertical solid lines denote the upper and lower central borders. The dotted grey line corresponds to a probability of occurrence of y = 0.05, and its intersection(s) with the response curve marks the lower and / or upper limit.
Table 1.
Modeling set-up with 14 different combinations of presence and frequency based on random sampling.
Four different presence scenarios (number of randomly selected presences being 10, 25, 50 or 100) combined with four different frequency scenarios (by varying the number of absences) were modeled. Two combinations could not be applied due to model restrictions or data paucity.
Fig 2.
Frequency distribution of model types chosen in the different Pre:Fre scenarios.
Dps gives the number of overall data points used for model fitting.
Fig 3.
Spearman-correlation matrices for all Pre:Fre scenarios.
Given are: a) model type (chosen most often from 100 repetitive model fittings for each species), b) optimum, c) lower limit and d) upper limits. Central numbers show the correlation coefficients. In a) axes are sorted based on the number of data points used for fitting. For b)–d) axes are sorted by frequency and presence numbers.
Fig 4.
Results of the linear mixed model identifying the trends of niche parameters.
Results for a) Index of Qualitative Variation (IQV), b) optimumany, c) LowLimany and d) UppLimany along the frequency gradient for all four Pre scenarios are presented. Colored lines show the regressions for every single species, whereas the black line reflects the mean across species (the population trend).