Lineage Diversification and Niche Evolution in the Chinese Cobra Naja atra (Elapidae)

The role of niche evolution (niche conserva tism or niche divergence) in lineage diversification is a poorly studied area. The Chinese cobra Naja atra (Elapidae) has diverged into three lineages: Lineage E in eastern China, Lineage S in southern China and Vietnam, and Lineage W in western China. However, whether the ecological niche is conserved or divergent among these three lineages is unknown. In the present study, we used ecological niche models in geographical space to study the ecological differences among lineages. We compared the niche overlap in environmental space to test niche conservatism and niche divergence. Our results showed that the three lineages of N. atra shared an ecological niche space between Lineages E and S/W, with the climatic niches of Lineages S and W representing a specialized fraction of the climatic niche of Lineage E. We speculated that the niche divergence between Lineages S and W was a consequence of geographical barriers limiting gene flow. Our study provides evidence for lineage diversification associated with both geographical isolation and climatic niche evolution, suggesting that early niche divergence between Lineages S and W, followed by niche conservatism, causes niche divergence among lineages.