Key points are not available for this paper at this time.
Michael R. Willig, S. Kathleen Lyons, An Analytical Model of Latitudinal Gradients of Species Richness with an Empirical Test for Marsupials and Bats in the New World, Oikos, Vol. 81, No. 1 (Feb., 1998), pp. 93-98
Willig et al. (Sun,) studied this question.