Cytotaxonomical Studies in South Indian Ranunculaceae

Abstract

Fifteen species of Ranunculaceae under eight genera have been studied, mostly collected from different regions of Ooty and Kodaikanal of Western Ghats. First record of chromosome numbers has been made in Ranunculus wallichianus, R. subpinnatus, R. reniformis, Clematis wightianus, Thalictrum dalzellii and T. saniculaeforme. On the basis of previous and present cytological data, there are n=7 and n=8 series in Ranunculus. All the species of Ranunculus studied here are higher polyploids and both aneuploidy and euploidy play important role in speciation.
The previous karyological analyses of Anemone reveal two distinct series, one with n=8 and the other n=7. Both A. rivalaris and A. japonica have 2n=24 chromosomes and they should have derived from n=8 series. Both in the larger size and the same number of chromosomes, Naravelia zeylanica and Clematis wightianus are related together.
The presence of fewer number of chromosomes and larger size of them indicates that Nigella damascena is a primitive species. All the three species of Thalictrum, namely T. javanicum, T. dalzellii and T. saniculaeforme possess 2n=16 chromosomes and perhaps, these taxa are diploids derived from n=8 series. The chromosomes are comparatively smaller in size in all these species.
Aquilegia canadensis has 2n=32 chromosomes. This may be a polyploid and it should have originated from n=8 basic chromosome series.
The population of Delphinium ajacis studied here is a diploid and that of D. belladonna a triploid and the basic chromosome number in Delphinium may be n=8. As far as this genus is concerned, higher polyploidy plays important role in specification.
In general, the taxa of Ranunculaceae studied show a wide range of chromo-some numbers from 2n=12 to 2n=46. As most of the taxa studied show either 2n=16 or multiples of n=8, the basic number of the family may be n=8 and the other basic numbers should have derived from it. The species are highly variable and polyphyletic in nature, as evidenced by the wide range of chromosome numbers, chromosome sizes and total chromosome lengths of various species studied.