Latitudinal concordance between biogeographic regionalization, community structure, and richness patterns: a study on...

Latitudinal patterns in species richness may be affected by both continuous variations in macroecological factors as well as discrete change between biogeographic regions. We examined whether latitudinal reptilian richness and community structure in China were best explained by three macroecological patterns (mid-domain effects, Rapoport's rule effects, or environmental correlates) within or across the ranges of biogeographic realms. The results showed that (1) there was a weak mid-domain effect within the Oriental Realm. However, the mid-domain effect was detected neither at the overall regional scale nor in the Palaearctic Realm. (2) Rapoport's rule was only weakly supported for reptilian fauna in China at lower latitudinal areas. (3) Environmental variables were more strongly correlated with species' latitudinal community structure and richness patterns at the scale of biogeographic realms. Based on the faunal similarity of reptilian community across latitudinal bands, we proposed a latitudinal delineation scheme at 34° N for dividing East Asia into Oriental and Palaearctic biogeographic realms. At last, at the functional group level, we also evaluated the relevant ecological patterns for lizard and snake species across different latitudinal bins, showing that the distributions of lizards presented strong mid-domain effects at the latitudinal ranges within the Oriental Realm and over the whole range but did not support Rapoport's rule. In comparison, snake species supported Rapoport's rule at low latitudinal zones but did not present any remarkable mid-domain effects at any spatial extents. In conclusion, biogeographic realms are an appropriate scale for studying macroecological patterns. Reptilian latitudinal richness patterns of China were explained by a combination of environmental factors and geometric constraints, while the latitudinal community structure patterns were greatly affected by environmental gradients. Functional guilds present differentiated macroecological patterns along the latitudinal gradients.