the phylogeography of this group provides examples of various speciation mechanisms at work in this scenario ancestors of this group became isolated from the remaining ilex when the earth mass broke away into gondwana and laurasia about  million years ago resulting in a physical separation of the groups and beginning a process of change to adapt to new conditions this mechanism is called allopatric speciation over time survivor species of the holly genus adapted to different ecological niches this led to reproductive isolation an example of ecological speciation in the pliocene around five million years ago mountain formation diversified the landscape and provided new opportunities for speciation within the genus