Distribution and threat status of the cytotypes of Pteris vittata L. (Pteridaceae) species complex in India

In India, Pteris vittata L. is very common and widely distributed. This fern is reportedly a 'species complex' and includes five cytotypes, viz. diploid, triploid, tetraploid, pentaploid and hexaploid with the basic number being 29 chromosomes. A survey of the literature indicated that some of the cytotypes were reported and collected only once or twice and never thereafter. In order to determine the current availability of these cytotypes, several collection excursions were undertaken, and a number of plants were collected from all over India and maintained in the fernery at National Botanical Research Institute (NBRI), Lucknow, India. In the absence of clear morphological characters specific to any cytotype, only the chromosome analysis of these plants confirmed their ploidy status. It was observed that only the tetraploid form was collected from different places. The hexaploid first reported in South India was not traceable during subsequent collection trips to this region. Similarly, in none of our collection trips did we come across any diploid form. In case of the triploid and pentaploid cytotypes, the only specimen available are those maintained in the NBRI fernery ever since their first report. The cytological abnormalities and reproductive failures along with other factors are probably responsible for the extinction of the cytotypes in their natural habitats. Thus in India, only the tetraploid cytotype is abundant while diploid and hexaploid are probably extinct. The triploid and pentaploid cytotypes, represented only by the limited specimens maintained at NBRI fernery, must also be considered as extinct in natural habitats.