The major tribes and sub-families of grasses occupy worldwide latitudinal belts, which can be related to an evolutionary sequence of climatic adaptations. However, genera tend to be confined to individual continents, suggesting that grasses do not easily cross the oceans, and that the worldwide distribution of the family may have been achieved when the continents were closer together. Species distributions are likewise strongly influenced by the effect of climatic adaptation and continental isolation, but they show a number of aberrations. These are probably a legacy of climatic disturbance during the Pleistocene.
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