Saxifragales

The Saxifragales (saxifrages) are an order of flowering plants (Angiosperms). They are an extremely diverse group of plants which include trees, shrubs, perennial herbs, succulent and aquatic plants. The degree of diversity in terms of vegetative and floral features makes it difficult to define common features that unify the order. In the Angiosperm Phylogeny Group classification system, the Saxifragales are placed within the major division of flowering plants referred to as eudicots, specifically the core eudicots. This subgroup consists of the Dilleniaceae, superasterids and superrosids. The superrosids in turn have two components, rosids and Saxifragales. The Saxifragales order has undergone considerable revision since its original classification, which was based purely on plant characteristics. The modern classification is based on genetic studies using molecular phylogenetics. There is an extensive fossil record from the Turonian-Campanian (late Cretaceous) time, about 90 million years ago (Myr). However, molecular studies suggest an earlier origin in the early Cretaceous (102–108 Myr) with rapid early diversification to more modern forms. The order Saxifragales consists of 15 families, about 100 genera and 2,470 species. Of the 15 families, many are small, with 8 having only a single genus, the largest family being the Crassulaceae (stonecrops) with about 35 genera. Saxifragales are found worldwide, though rarely in the tropics, and in a wide variety of habitats from desert to aquatic. They also have a wide variety of uses, from timber to foodstuffs and ornamental plants. Apart from ornamentals, the major economically important group is the Grossulariaceae (currants and gooseberries), particularly blackcurrant. The order Saxifragales is extremely morphologically diverse (hyper-diverse). It includes trees (e.g. witch hazel, witch alder in Hamamelidaceae), fruit bearing shrubs (e.g. currants, gooseberries in Grossulariaceae), lianas, annual and perennial herbs, rock garden plants (e.g.