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

Cytogenetic investigations of 13 natural populations of Coptis teeta, an en demic and endangered medicinal plant from the Eastern Himalaya, were carrie d out. About 70-80% individuals in some of the populations were synaptic mu tants. The predominantly sexually breeding plant populations were confined to higher cooler latitudes, whereas the mutant apomict inhabited lower wann er latitudes. The breeding systems were observed to be associated with morp hological differentiation and ecological preference of some populations. In dividuals of subsp. tata reproduced sexually as well as vegetatively, but t hose of subsp. lohitensis have adapted almost entirely to a vegetative mode of reproduction. Though no variation was observed in somatic chromosome nu mber and karyotypes, the two subspecies differed significantly with respect to their. male meiotic behaviour and rhizome morphology. The mutants eithe r produced little fertile pollen or wore completely sterile, leading to low seed production or none at all. This has resulted in low reproductive fitn ess, localized distribution and small population sizes of the taxon. (C) 20 00 The Linnean Society of London.