opinion: Relationship between local population density and environmental suitability estimated from occurrence data

Abstract

Figure 1. Idealized triangular relationship between suit-ability and abundance. Two vectors-one representing abundance (y) and another suitability (x)-were generated. In the case of x, 1000 values ranging between 0 and 1 were randomly extracted from a uniform distribution. In the case of y, 1000 values were also randomly extracted from a uniform distribution following the condition 0 ≤ y i ≤ x i (i = {1, …, 1000}). Linear quantile regressions were fitted to the 97.5 th percentile (red dashed line). From 1000 simulations, the mean goodness-of-fit statistic for quantile regressions (R 1 ; Koenker and Machado 1999) was computed, with a value of 0.60. Analyses were done in R using the quantreg package (Koenker 2009).