The spatial distribution of mistletoe in a Southern Indian tropical forest at multiple scales

Abstract

Taxillus tomentosus is a mistletoe of significant management concern in southern India. This mistletoe affects the productivity of several nontimber forest products, most significantly Amla (Phyllanthus emblica and Phyllanthus indofischeri), whose fruits provide an important source of income for indigenous forest communities. Management interventions are required to secure the continued viability of Amla and thereby its role in livelihoods. To enhance the scientific basis for management, we characterized the distribution of T. tomentosus at three scales, examined potential mechanisms underlying this distribution, and compared both with those documented in other habitats. Mistletoes were aggregated at all three scales: on individual trees, within forest plots of 500 m², and at scales of 3-4 km. Seed deposition patterns provide an initial distribution 'template' that largely determines patterns at tree and plot scales. This initial pattern is subsequently altered as variation in host suitability and mistletoe mortality from forest fires influence establishment success and postestablishment survival. Local prevalence of infection contributed most to infection spread, and areas of high infection prevalence are highlighted as appropriate foci for management intervention. Although novel underlying mechanisms and variation in the scale of aggregation have been identified, mistletoe distribution in a tropical forest appears to be shaped by similar forces as those documented previously in temperate systems.