Chromosome Counts for the Asian Myristicaceae (Magnoliales)

Abstract

Myristicaceae, a family with pantropical distribution and sister to the rest of the Magnoliales, are poorly understood with respect to chromosome numbers. Here we report somatic chromosome numbers of 14 species in five of the six Asian genera. Chromosome numbers were consistent within individual genera but markedly differ among the genera. Based on our observations, we concluded that the generic base number is x=20 in Endocomia, x=22 in Gymnacranthera and Knema, x=25 in Myristica, and x=26 in Horsfieldia. Although reliable data on chromosome numbers are currently limited to Asian genera, a great divergence in base numbers is a marked contrast to the low molecular divergence within the family, casting a doubt to dating Myristicaceae to be young.