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 B 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 ÃŽÂ² diversity, in the tropics compared to temperate regions. Here, we leverage a large botanical dataset to map taxonomic and phylogenetic ÃŽÂ² diversity, as mean turnover between neighboring 100 ÃƒÂ— 100 km cells, across the Americas and determine key climatic drivers. We find taxonomic and tipÃ¢Â€Âweighted phylogenetic ÃŽÂ² diversity is higher in the tropics, but that basalÃ¢Â€Âweighted phylogenetic ÃŽÂ² diversity is highest in temperate regions. Supporting Janzen's Ã¢Â€Â˜mountain passesÃ¢Â€Â™ hypothesis, tropical mountainous regions had higher ÃŽÂ² diversity than temperate regions for taxonomic and tipÃ¢Â€Âweighted metrics. The strongest climatic predictors of turnover were average temperature and temperature seasonality. Taken together, these results suggest ÃŽÂ² diversity is coupled to latitudinal richness gradients and that temperature is a major driver of plant community composition and change.