Species Density of North American Amphibians and Reptiles

<it>Kiester, A. R. (Dept. Zoology, Univ. Calif., Berkeley, Calif. 94720),</it><cross-ref type="fn" refid="fn1">1</cross-ref> <it>1971. Species density of North American amphibians and reptiles. Syst. Zool., 20:127–137</it>. Species density matrices and contour maps are presented for the amphibians and reptiles of the United States and Canada. Both classes show a regular southward increase in average density, and these patterns together with those of birds and mammals are analyzed to show the effects of topographic variability on species density. Some problems and theories about latitudinal gradients in diversity are discussed. A longitudinal complementarity between mammals and reptiles is demonstrated and some possible causes are discussed.