Synaptic mutation associated with gametic sterility and population divergence in Coptis teeta (Ranunculaceae)

Abstract

Cytogenetic investigations of 13 natural populations of Coptis teeta, an endemic and endangered medicinal plant from the Eastern Himalaya, were carried out. About 70–80% individuals in some of the populations were synaptic mutants. The predominantly sexually breeding plant populations were confined to higher cooler latitudes, whereas the mutant apomict inhabited lower warmer latitudes. The breeding systems were observed to be associated with morphological differentiation and ecological preference of some populations. Individuals of subsp. teeta reproduced sexually as well as vegetatively, but those of subsp. lohitensis have adapted almost entirely to a vegetative mode of reproduction. Though no variation was observed in somatic chromosome number and karyotypes, the two subspecies differed significantly with respect to their male meiotic behaviour and rhizome morphology. The mutants either produced little fertile pollen or were completely sterile, leading to low seed production or none at all. This has resulted in low reproductive fitness, localized distribution and small population sizes of the taxon.