Abstract
Cytological investigations were carried out on 24 taxa representing Aristolochia subgenera Siphisia and Aristolochia. Of them, 17 taxa (16 species and one variety) were examined for the first time. In subgeneus Siphisia, all the eight species, A. austoyunnanensis, A. kwangsiensis, A. macrophylla, A. moupiensis, A. nakaoi, A. paracleta, A. salvadorensis and A. tricaudata show the same number of 2n=32. While in subgenus Aristolochia three different chromosome numbers were observed ; 2n=16 in A. maxima and A. ovalifolia ; 2n=14 in A. arcuata, A. argentiana, A. clematitis, A. cymbifera var. abbreviata, A. fimbriata, A. goliathiana, A. macroura, A. micrantha, A. odoratissima, A. ringens and A. tiangularis ; 2n=12 in A. jackii, A. kankauensis and A. tagala. The chromosome numbers obtained are relatively well in congruence with the classification system and with the molecular phylogeny. Based on the present and previous studies the subgenus Siphisia is characterized by the number 2n=32. In contrast, the subgenus Aristolochia is diversified in chromosome number, showing the three different numbers. Subsection Podanthemum and series Thyrsicae seem to be characterized by the numbers, 2n=12 and 2n=16, respectively.
