McFadden, Ian R.; Sandel, Brody; Tsirogiannis, Constantinos; Morueta-Holme, Naia; Svenning, Jens-Christian; Enquist, Brian J.; Kraft, Nathan J.B. 2019. Temperature shapes opposing latitudinal gradients of plant taxonomic and phylogenetic Î² diversity. Ecology Letters. (Abstract) (Online version)
Latitudinal and elevational richness gradients have received much attention from ecologists but there is little consensus on underlying causes. One possible proximate cause is increased levels of species turnover, or Î² diversity, in the tropics compared to temperate regions. Here, we leverage a large botanical dataset to map taxonomic and phylogenetic Î² diversity, as mean turnover between neighboring 100 Ã— 100 km cells, across the Americas and determine key climatic drivers. We find taxonomic and tipâ€weighted phylogenetic Î² diversity is higher in the tropics, but that basalâ€weighted phylogenetic Î² diversity is highest in temperate regions. Supporting Janzen's â€˜mountain passesâ€™ hypothesis, tropical mountainous regions had higher Î² diversity than temperate regions for taxonomic and tipâ€weighted metrics. The strongest climatic predictors of turnover were average temperature and temperature seasonality. Taken together, these results suggest Î² diversity is coupled to latitudinal richness gradients and that temperature is a major driver of plant community composition and change.