Biodiversity higher in the tropics, but species more likely to arise at higher latitudes
A study of 2300 species of mammals and 6700 species of birds helps explain why there are more species in the tropics than at higher latitudes. Researchers found that while the tropics harbor more species, the number of subspecies increases in the harsher environments typical of higher latitudes. The results suggest that the latitudinal diversity gradient may be due higher species turnover -- speciation counterbalanced by extinction -- towards the poles than near the equator.<img src="http://feeds.feedburner.com/~r/sciencedaily/~4/2Sy391n2c4I" height="1" width="1"/>
