The remaining diversity of conifers

Compared with the gigantic diversity of angiosperms (c. 400,000 species), the gymnosperms, once one of the dominant plant types on Earth, are at present, with c.900 species, a tiny minority. With some 630 species in 70 genera and 8 families, the conifers form the bulk of this remnant diversity, the remainder being mostly cycads plus ephedras, gnetums, Welwitschia and Ginkgo. The conifers, though presently recognised as a monophyletic group in relation to other seed plants, are nevertheless a typical mixture reflecting two phenomena: extinction and radiation. The author recognises three families with but a single genus, one family with a single species, and numerous unispecific genera. This classification reflects extinction of closely allied lineages rather than character accumulation within single taxa. In other families, some genera are prolific in species and many of these are rapidly evolving (e.g., Pinus) and widely spread and successful in certain environments related to severe climatic change (e.g., Juniperus). Such genera display radiation. Conifers, despite their minute diversity in comparison with angiosperms, occupy an enormous range of environments on all continents but Antarctica, where they became extinct. The author presents an overview of this diversity.