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Oryza malampuzhaensis Krish. et Chand., one of the tetraploid taxa in the genus Oryza (Poaceae), is geographically restricted to Western Ghats, southern India. This is one of the poorly understood taxa in the genus, and not much is known about the nature and distribution of its genetic diversity. Five individuals each were selected randomly from 11 populations of O. malampuzhaensis from different altitudinal habitats and were grown in a common-garden experiment for 3 years (1994-1997). Sixty morphological traits and 87 random amplified polymorphic DNA (RAPD) markers, generated by 14 random primers, were used to study the genetic variation among the populations. Elevation-dependent phenotypic variation was observed for a suite of metric traits. A scatterplot of mean values for these traits separated the populations from low, middle, and high altitudes into distinct groups. Cluster analysis using RAPD distance grouped the populations according to their altitudinal habitat, and a similar pattern of clustering was observed with respect to morphological distance also. The mean of both RAPD- and morphology-based pairwise genetic distance of populations belonging to similar altitudinal levels differed significantly. These estimates also depicted a significant decrease in genetic distance with increasing altitude. The results demonstrate that (i) effective isolation from gene flow coupled with natural selection governs genetic structure in O. malampuzhaensis and (ii) ecological heterogeneity associated with elevational gradient has a crucial role in the evolution of O. malampuzhaensis.Key words: Oryza malampuzhaensis, altitude, RAPD, morphological traits, genetic variations, molecular ecology. |
