A karyomorphological study of 40 species in 11 genera of the Magnoliaceae from China

Abstract

In this paper, 40 species in 11 genera of the Magnoliaceae from China were karyomorphologically investigated for a better understanding of the intergeneric relationships in the family and the systematic positions of some species, particularly those in the genus Manglietia. The 20 Manglietia species studied are all diploid with 2n=38, indicating that in this genus the speciation may have taken place predominantly at the diploid level and that minor structural changes of chromosomes may have resulted in distinct morphological divergence. In the genus Magnolia, cytotypes with various ploidy levels from 2x to 6x have been found, which may be, at least to some degree, associated with the wide distributional range and complex gross-morphological variation of the genus. Our results indicate that Manglietia should be an independent genus from Magnolia and do not support the treatment of merging them as a genus. All the Michelia species already with chromosome numbers are diploid with 2n=38, while most of the species in Magnolia subgen. Yulania are polyploid, suggesting that Michelia is not closely allied with Yulania and that the two groups should not be merged as a genus. All Parakmeria members are polyploid. It is noteworthy that cytological evidence is generally less informative in clarifying the intergeneric relationships of the Magnoliaceae than the interspecific relationships within a given genus of the family because reticulate evolution may have extensively occurred in this family. Systematic positions of some species in Manglietia are discussed based on evidence from cytology, morphology and geographical distribution.