Zhang Xin-Hua, Xia Nian-He. CARYOLOGIA. 2007, 60 (1-2): 52-63

ABSTRACT: A karyomorphological study on eleven and one hybrid belonging to Michelia L. and Manglietia Blume (Magnoliaceae, sensu stricto) was conducted, The structure of interphase nuclei and prophase chromosomes of representatives of the two genera were presented here for the first time. Three karyomorphological types at resting nuclei and two types of prophase chromosomes were recognized according to TANAKA'S catalogue (1971; 1977; 1980) respectively. It might provide information to distinguish the intergeneric and infrageneric relationships in Magnoliaceae. An evolutionary trend is proposed that awaits verification by further study. All taxa studied have the same diploid number of chromosomes (2n=38) in somatic cells, three of them were reported for the first time, and others were comfirmed. The karyotype analysis have shown a predominance of chromosomes with centromeres in a median position and a few submedian centromeres, except for Michelia hypolampra with subterminal and terminal point centromeres, which also showed high karyotypic symmetry. The karyotype data documented with 2n=38 indicate that the speciation may have taken place predominantly at the diploid level in Michelia and Manglietia and that minor structural alternation of chromosomes may have resulted in distinct morphological divergence and probably played the most important role in the evolution of genus and species.