The prerequisite of any program aimed at studying genetic variations is to understand distribution pattern of the target species (Bothmer and Seberg, 1995). Because the sampling procedures should recover the greatest amount of the genetic variation of the species, irrespective of the relative frequency or rarity of any genes or linked genetic combinations (Bogyo et al., 1980). In the present study, information available in floras, review articles and other related published literature was utilized to get a clear picture on the distribution of the species (Fig. 5.1). Even though A. paniculata is distributed over a broad ecogeographical range, the so called ‘native populations’ occur only in south India and Sri Lanka (Hooker, 1885; Bhat and Nanavati, 1978). Available literature also suggests that the populations found in North India, Java, Malaysia, Indonesia, West Indies, and elsewhere in Americas are ‘introduced’ (Hooker, 1885; Ridley, 1967; Backer and Brink Jr., 1967; Correll and Correll, 1982). In this study, natural populations along with a few introduced ones were included.
Apart from the wide geographical range of distribution, the habitat preferences of A. paniculata were also wide. The range of habitats (sea shore, river bed, scrub jungle, rocky exposures, fallow lands, way side, backyard of houses in villages) in which the plants were collected is indicative of the ability of the species to colonize newer areas. Besides, being a member of the family Acanthaceae, the species is well specialized in profuse setting of seeds and dispersal of the same by a rather violent bursting of the capsules. The seeds so dispersed could be easily carried away by water to distant places during the rainy season. There is no wonder therefore that this species is not likely to be endangered in the places where it occurs though genetic depletion due to indiscriminate collection might be a reality. Observations in the field also revealed luxuriant growth and seed setting in wet regions of Kerala and Kollidam and stunted growth and poor seed production in plants growing in rocky exposures of Algar Hills, probably accounting for differences in seed viability between collections recorded in the study.
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