SPECIES RICHNESS AND LATITUDE
Species richness of low-latitude communities (communities closer to the equator) is greater than species richness of high-latitude communities (ones farther from the equator). In part, this is because species richness decreases as the habitat's environmental stress goes up. Communities at high latitudes suffer from harsher climates than communities close to the equator. Greater species richness is generally associated with reduced seasonality or more environmental stability.

Communities near the equator gain more solar energy, which may enable more species to coexist. This is called the species richness-energy hypothesis. Ecuador, for example, contains more than 1,300 bird species, twice the number living in the United States and Canada combined.