This week at Nothing in Biology Makes Sense!, Noah Reid describes a new study that tries to explain the latitudinal biodiversity gradient—that is, the reason why a tropical rainforest has so many more species than, say, the mighty forests of British Columbia.
Almost invariably across taxonomic groups, hemispheres and continents, as one moves from polar regions towards the equator, species diversity increases (see the figure for a depiction of global bird diversity). The concept of diversity here can be broken down into three parts: “alpha diversity” or the diversity of species in a single location; “beta diversity”, or the turnover of species observed when moving among locations; and “gamma diversity” or the diversity of species found in an entire region. The latitudinal diversity gradient holds true for all three elements.
To find out what the new study reveals, go read the whole thing. ◼