Cytology and its Bearing on the Systematics and Phylogeny of the Piperaceae.

Abstract

Systematic relationships and phylogeny of the Piperaceae are discussed in the light of chromosome data, with special reference to the South Indian taxa which comprise 17 species of Piper, 8 species of Peperomia and the monotypic Heckeria. Chromosomes of species of Piper are very small sized, and those of Peperomia large sized, while Heckeria has medium sized chromosomes. Species of Piper and Peperomia are x=13 and x=11 basic respectively occurring at different ploidy levels; and the species of Heckeria is a diploid on x=13. It is postulated that the Piper group had diversified much earlier than Peperomia so much so the former had enjoyed a much longer evolutionary span than Peperomia during which appropriate chromosome structural changes have operated more in Piper leading to marked size diminution of chromosomes. It is evident that karyomorphologically the genus Piper is more evolved than Peperomia. The genus Peperomia (x=11) appears to be a connecting link between Piperaceae and Saururaceae (x=11). The marked karyological distinction between Piper and Peperomia noticed in the South Indian taxa provides confirmatory evidence in support of the proposed segregation of Peperomia to separate family rank (Peperomiaceae).