Oleaceae
Overview

The type genus for Oleaceae is Olea, the olives. Recent classifications recognize no subfamilies, but the family is divided into five tribes. The distinctiveness of each tribe has been strongly supported in molecular phylogenetic studies, but the relationships among the tribes were not clarified until 2014. The phylogenetic tree for Oleaceae is a 5- grade that can be represented as {Myxopyreae }.

The major centers of diversity for Oleaceae are in Southeast Asia and Australia. There are also a significant number of species in Africa, China, and North America. In the tropics the family is represented in a variety of habitats, from low-lying dry forest to montane cloud forest. In Oleaceae, the seed dispersal is almost entirely by wind or animals. In the case that the fruit is a berry, the species is mostly dispersed by birds. The wind-dispersed fruits are samaras.

Some of the older works have recognized as many as 29 genera in Oleaceae. Today, most authors recognize at least 25, but this number will change because some of these genera have recently been shown to be polyphyletic.

Estimates of the number of species in Oleaceae have ranged from 600 to 900. Most of the species number discrepancy is due to the genus Jasminum in which as few as 200 or as many as 450 species have been accepted.

In spite of the sparsity of the fossil record, and the inaccuracy of molecular-clock dating, it is clear that Oleaceae is an ancient family that became widely distributed early in its history. Some of the genera are believed to be relictual populations that remained unchanged over long periods because of isolation imposed by geographical barriers like the low-elevation areas that separate mountain peaks.
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