The cytology of Actinidia, Saurauia and Clematoclethra (Actinidiaceae)

Abstract

Clematoclethra lasioclada Maxim. The chromosome numbers of Saurauia tristyla and S. miniata were 2 n = 6 x = 78, establishing a base chromosome number of x = 13 in the genus, differing from the previous report of x = 15. The chromosome number of Clematoclethra was first reported to be 2 n = 4 x = 48 ( x = 12), while that of Actinidia was x = 29, consistent with previous reports. The base chromosome number of Clematoclethra ( x = 12) was derived from an aneuploid decrease from Saurauia ( x = 13). Actinidia (x = 29) was derived from the palaeotetraploid ( x = 14), which was formed through the increase of the basic chromosome number x = 13 to x = 14 by aneuploidy and through the breakage of a centromere to add one more new chromosome. The chromosome data in Actinidia were consistent with the geographical and morphological evidence for the evolution of the three genera. The tropical American and Asian disjunct distribution pattern and the diversity of base chromosome numbers of Saurauia further support the probability that the genus was an early divergent from a common ancestor of Actinidia and Clematoclethra .