The compositae revisited

Abstract

Bentham’s treatment of the Compositae in the Genera Plantarum is still, after more than a century, the most important basic reference work on the family. The scholarly challenge to Bentham’s views by Small in 1917–1919 is severely compromised by Small’s reliance on the Age and Area hypothesis. In 1955 I published a comprehensive paper on the phylogeny and taxonomy of the Compositae. My outlook was highly compatible with that of Bentham, as it remains today.

A significant change in my views after 20 years is that I now take the woody habit to be primitive within the family, and the herbaceous habit derived, rather than the other way around. Many of the herbs have retained an active cambium, however, and some of these have reverted to a secondarily woody habit.

The fossil record does not connect the Compositae to any other group. Recog nizable members of the family can be traced back to the top of the Oligocène epoch. Some of the older fossils that have been referred to the Compositae, such as the Upper CretaceousPalaeanthus problematicus, clearly do not belong, and others are at best doubtful.

The ancestry of the Compositae remains in dispute. A long series of extinct forebears must be postulated in order to relate them to anything at all, and the chemical data are not in harmony with the morphological data. The most similar modern family is the Calyceraceae, but these can be no more than collateral rela tives. I still hold to the view that the ancestry of the Compositae probably lies in the vicinity of the Rubiaceae.

There is now a ferment about tribal classification in the Compositae, and several new tribes have recently been proposed. The least controversial of these is the Liabeae, which seems likely to become generally accepted. Application of recent chemical data may lead to further restriction of the Senecioneae, with several genera being transferred to the Heliantheae or elsewhere. It now seems to be generally agreed that Bentham’s tribe Helenieae must be dismembered, and that at least some of its components must be included in a more broadly defined tribe Heliantheae. Elevation of the Tagetinae to tribal status can be defended on both morphological and chemical grounds, but may not be necessary, since the rela tionship of the Tagetinae to the Heliantheae is clear.

Carlquist’s recent proposal to organize the tribes of Compositae into two sub families of 6 tribes each is interesting but faulty. It has the virtue of putting most of the radiate tribes into one subfamily, but it minimizes the significance of the Arctotideae as a group connecting the radiate tribes to the discoid ones. Furthermore, it ignores the most obvious dichotomy in the family, which separates the Lactuceae from all the remaining tribes.