Determination of the scale of pattern and distribution in Helicteres isora L (Sterculiaceae)

Abstract

Helicteres isora L. is a traditional multipurpose plant used by indigenous community and villagers inall the three major climatic zones in Sri Lanka. It naturally occurs in the edges of forests and indisturbed secondary vegetation. It is fastly disappearing in the wet zone due to land clearing and highextraction rates. The present study was conducted to understand the pattern and the scale of distributionof H. isora in order to provide information for biodiversity conservation and further to enable thesustainable use.

Twelve natural populations were identified in wet, intermediate and dry zones and the distribution ofindividuals was studied using gradient directed transect method. The t test was performed for eachpopulation to detect the pattern of distribution and pattern analysis was carried out to determine thescale of pattern.

Out of twelve populations surveyed, only five populations showed contagious distribution (p < 0.05)while seven populations showed random pattern of distribution. This indicates that the populations ofH isora do not fall into a particular pattern of distribution in nature. This may be due to the highdisturbance present in and around the populations.

The results of the pattern analysis reveal more peaks in smaller block sizes (2m2) and larger blocksizes (32m2) indicating aggregated pattern in respective block sizes. Peaks in smaller block sizes aredue to the morphology of the plant as it produces new plants from roots. Peaks at larger block sizesare due to the extrinsic factors and these results could be utilized in the in- situ conservation of Hisora .