No abstract

No abstract

Summary A detailed chromosome study has been made of 58 species in 30 genera of the tropical family Meliaceae. The results largely confirm observations, by other investigators on similar tropical woody groups, that high chromosome numbers are common and that polyploidy is a frequent phenomenon. Although the chromosomes are, in most species, very small and metacentric, some differences in chromosome size and shape are detectable. Many genera seem to have a high base number and/or several different numbers. The Meliaceae, unlike some other tropical woody groups, are particularly interesting because of the considerable range of chromosome numbers they exhibit. Differences in number have been observed between even closely related species in the economically important timber genera Swietenia, Cedrela and Toona, and this has an obvious bearing on future tree breeding and tree improvement studies. The taxonomic significance of chromosome numbers is discussed.

Variation in the pseudostrobus group of species in Pinus was examined using a series of numerical techniques involving principal components and canonical discriminant analyses. As a result, the group is divided into three species: P. maximinoi, P. douglasiana and P. pseudostrobus. The latter, which is very variable, is further divided into two subspecies and one variety. The formal taxonomy of the group is revised and information on the distribution, ecology and relationships of the taxa recognized is given. Because of the very great economic importance of these pines within and outside their natural distribution areas and the considerable nomenclatural confusion which exists, a full treatment of synonymy and relevant literature is provided.

No abstract