Principal component analysis.

<p>The gray dots represent the multivariate climatic space of the distribution of <i>L</i>. <i>catesbeianus</i> in the United States and Mexico. The yellow dots indicate the distribution of bullfrogs in climate space of native range, dark blue dots shows the distribution of this frog in climate space of Zone A (Sonora and Chihuahua), red dots in Zone B (Baja California Sur), green dots in Zone C (Sinaloa) and brown dots in Zone D (Veracruz, Hidalgo, Michoacán and Morelos).