Species Diversity at Wet Tropical Environment I. Polymorphic Variation and Population Structure of Schismatoglottis lancifolia (Araceae) in West Sumatra

Abstract

Schismatoglottis lancifolia (Araceae) is a forest floor herb in tropical rain forest and a native of Sumatra. It shows a typical outcross pollination and protogyny, i.e., the male flowers supply pollen grains one day after the female matures. The pollinator is some Diptera and/or small beetles and the pollen flow seems to be restricted in small area. The reproduction is carried out mainly by seeds with a few exception of vegetative propagation. The population of S. lancifolia preserves several polymorphic characters in not only phenotype but also karyotype, e.g., the color of beneath of the leaf, presence or absence of leaf surface mottle, type of satellite chromosome, and the number of B-chromosome. We analyze the polymorphic variations in these characters at different populations to clarify the population structure and the infra-species diversity. Sixty-one sites in 13 locations, including four plots for forest ecological survey were studied. The spatial position of individuals at these plots, Gajabuih, Pinang Pinang, Pinang Pinang Atas and Airsirah, are recorded on the maps for further analysis, and put together into clones judged from spatial arrangement, karyotype and leaf characters. The m-m methods are applied for the analysis of the spatial distribution patterns of both individuals and clones. The results indicate the existence of double clump structure in populations; smaller clump is calculated to be of about 1 ㎡, while larger the one is of about 100 ㎡ which is looser than the former. By these analyses the hierarchy of population structure is clarified as; micro-, breeding-, topo- and local-population. Variation patterns of characters in locations (almost the same as topo-populations) are classified into two types. One is that the ratio of each character fluctuates location by location. Leaf beneath color and B-chromosome show this pattern. The other pattern is that the ratio of each character takes rather constant value irrespective of location. Leaf mottle and satellite chromosome display this pattern. The correlation between some environmental gradients and ratios of the characters are analyzed. None of the characters are associated with environmental gradient, but the possibility that the polymorphism is maintained by different selection direction under different microhabitat is still a matter of debate.