Cross-taxon congruence in a trekking corridor of Sikkim Himalayas: Surrogate analysis for conservation planning

Abstract

Summary The use of surrogate taxon in conservation planning has become an important tool in the recent years. Woody tree, bird and butterfly diversity indices were used to investigate their potential as surrogates in the Sikkim Himalayas. Woody trees, birds and butterflies were surveyed in 19 permanent plots/transects at open (canopy cover 40%) forest conditions along two sets of forest types [warm temperate broadleaf forest (1780–2350 m), and cool temperate sub-alpine forest (2350–3600 m)] in the Khangchendzonga Biosphere Reserve of Sikkim Himalayas, India, during 1998-1999. Cross-taxon congruence among the three taxonomic groups was investigated along a 26 km trekking corridor to examine the extent to which these group of organisms can function as surrogates for each other. Diversity indices (Shannon diversity index and Margalef species richness) of the three taxonomic groups were used to assess the congruence pattern in open and closed canopy conditions within warm temperate broadleaf forest and cool temperate sub-alpine forest and the altitudinal gradients (irrespective of forests conditions and types). Although the woody tree, bird and butterfly diversity indices showed differences between the open and closed canopy conditions, they were insignificant. But, when they were compared between the warm temperate broadleaf forest and cool temperate sub-alpine forest, all of these indices were significantly related showing higher values in the warm temperate broadleaf forest and the pattern along the altitudinal gradients was found in to be in a decreasing order. In addition, simple regression among the three taxonomic groups and their Pearson correlations further supplemented the congruence patterns suggesting their potential for surrogates usable as a conservation planning tool. These congruence patterns are discussed in context of regional and global studies to validate its applicability for conservation and tourism planning.