S.G.A. Flantua

An early start for the Panama land bridge

The land bridge between North and South America formed 10 million years earlier than previously thought [Also see Report by Montes et al.] The birth of the Panama land bridge, which connects the Americas, has been associated with one of the biggest biological exchanges in Earth history as numerous species migrated from one continent to the other (1). Nevertheless, the timing of formation of the land bridge is still much debated (2). On page 226 of this issue, Montes et al. (3) propose that the Central American Seaway, which separated South and North America, closed about 15 to 13 million years ago, more than 10 million years earlier than previously thought (4), with important implications for ocean circulation, climate, and biotic exchange.

Geological and climatic influences on mountain biodiversity

Mountains are key features of the Earth’s surface and host a substantial proportion of the world’s species. However, the links between the evolution and distribution of biodiversity and the formation of mountains remain poorly understood. Here, we integrate multiple datasets to assess the relationships between species richness in mountains, geology and climate at global and regional scales. Specifically, we analyse how erosion, relief, soil and climate relate to the geographical distribution of terrestrial tetrapods, which include amphibians, birds and mammals. We find that centres of species richness correlate with areas of high temperatures, annual rainfall and topographic relief, supporting previous studies. We unveil additional links between mountain-building processes and biodiversity: species richness correlates with erosion rates and heterogeneity of soil types, with a varying response across continents. These additional links are prominent but under-explored, and probably relate to the interplay between surface uplift, climate change and atmospheric circulation through time. They are also influenced by the location and orientation of mountain ranges in relation to air circulation patterns, and how species diversification, dispersal and refugia respond to climate change. A better understanding of biosphere–lithosphere interactions is needed to understand the patterns and evolution of mountain biodiversity across space and time.Species richness in mountain environments is linked to mountain-building and climatic processes, an integration of geological, climatic, and biological datasets reveals.