Directional selection of bisexual plants in natural populations of Isoetes pantii (Pteridophyta: Isoetaceae) with chromosome evolution

Population biology studies during 1966-2010 have revealed that the proportion of bisexual plants has declined in natural populations of Isoetes pantii at Narsinghgarh (Central India), where it has been growing with the parental species I. coromandelina L. and I. sampathkumaranii Rao. Since many fundamental discoveries have been observed from within the microsporangia (male sporangia) over four decades the decline of production of male sporangia by this species has been briefly presented in the light of chromosomal as well as ecological factors. Directional selection appears to have favoured this decline.