Pinus classification

Pinus, the Pines, is a genus of approximately 111 extant tree and shrub species. The genus is currently split into two subgenera, subgenus Pinus (Diploxylon pines or Hard pines), and subgenus Strobus (Haploxylon pines or Soft pines). Each of the subgenera have several sections within based on chloroplast DNA sequencing. Older classifications split the genus with three subgenera, Pinus (Pinus), Pinus (Strobus), and Pinus (Ducampopinus) (Pinyon, Bristlecone and Lacebark pines)physical morphology of based on cone, seed and leaf characters. DNA phylogeny has shown that Pinus (Ducampopinus) species are members of Pinus (Strobus), and the subgenus Pinus (Ducampopinus) is no longer used.

Subgenus Ducampopinus was regarded as intermediate between the other two subgenera. In many classifications, it is combined into subgenus Strobus, but it was also included in subgenus Pinus in an early classification by the Californian botanist J G Lemmon in 1888, yet it did not fit entirely well in either so it was treated as a third subgenus in its own right. In general, cone and cone scale and seed morphology and leaf fascicle and sheath morphology were emphasized and this seemed to result in a classification that had subsections of pines that were understandable and usually readily recognized by their general appearance. Pines with one fibrovascular bundle per leaf, i.e. subgenera Strobus and Ducampopinus, were known as haploxylon pines, while pines with two fibrovascular bundles per leaf, i.e. subgenus Pinus, were called diploxylon pines. Diploxylon pines tend to have harder timber and more amounts of resin than the haploxylon pines.