Revista Chilena de Historia Natural 82 (1): 135-151, 2009
RESEARCH ARTICLE
Mammal and butterfly species richness in Chile: taxonomic covariation and
history
Understanding species richness spatial distribution is of fundamental importance to face
the current biodiversity crisis that affects biotas around the world. Taxonomical covariation in species occurrence may offer the
possibility to identify common factors that restrict species richness, as well as some guidelines to the identification of key areas for
conservation purposes. To this aim, we analyze the geographic distribution of mammals and butterflies in Chile using 0.5° latitude and
longitude quadrats. We found that, for both taxa, there is a strong bell-shaped latitudinal gradient in species richness with a peak at
mid-latitudes (33-43° S). The results from multiple stepwise regression analysis shows that for both taxa productivity measured using
the Normalized Difference Vegetation Index (NDVI) is the most important variable driving changes in species richness followed by
glaciation and elevation depending on the taxa. Mid-domain effects were either weak or unimportant in affecting the richness pattern.
Variance partitioning analysis shows that the spatial components alone are irrelevant to the richness pattern. We show that spatial
covariation in richness of butterflies and mammals, is strongly influenced by spatial scale, possibly as the result of a scale-dependent
effects on individual species ranges, whereas factors related to specific ecological characteristics, are more important at smaller
scales. Because richness gradients are ultimately the product of speciation and colonization processes on longer time scales, we
propose that species richness gradients in Chile may be explained by the interaction between historical processes associated to
desertification and glaciation together with productivity. The former sets the domain within which productivity produces a similar
richness pattern for both taxa despite their different phylogenetic histories and physiological requirements.
Key words:
lepidoptera, mammalia,
Chile, latitudinal gradient, species richness
