Does the Distribution of Breeding Bird Species Richness in Taiwan Follow the Mid-Domain Effect?

Abstract

In this paper, we examined the breeding bird species richness along an elevational gradient in northern Taiwan. These data obtained from 144 sites were used to test the mid-domain model. We compared the species richness with expectations from the mid-domain models, and identified elevational ranges at which the species richness was excessive or depauperate in species, relative to expectations. In addition, we compared the observed spatial distributions of geographic ranges with those predicted by mid-domain models to explore how species richness deviations were produced. Along the entire elevational gradient, observed species richness in most sites obviously deviated from those predicted by mid-domain models. We hypothesize that asymmetrical hump-shaped curve of the species richness may come from the combination of the favorableness hypothesis, the productivity hypothesis, and the mid-domain effect. Comparisons between observed and predicted spatial distributions of geographic ranges indicated that the nonrandomness of the distributions of endpoints or midpoints was highly congruent with vegetation transitions along the elevational gradient. The time hypothesis may account for the nonrandomness below 500m.