Do sub-groups of butterflies display different elevational distribution patterns in the Eastern Himalaya, India?

Sailendra Dewan,Sudeep Ghatani,Bhoj Kumar Acharya,Ole R. Vetaas

doi:10.21425/f5fbg49643

Abstract

Understanding the pattern of biodiversity along environmental gradients helps in identifying diversity hotspot areas that can be prioritized for conservation. While the elevational distribution of several taxa has been studied, responses of the sub-groups within a taxon to elevation and its associated factors are not properly understood. Here we study species richness and butterfly density along an elevation gradient in Sikkim, Eastern Himalaya, India and explore the underlying causes of the patterns. We sampled butterflies using a fixed-width point count method in 16 elevational bands (150–200 m intervals), between a range of 300 and 3300 m a.s.l. We categorized butterflies into various sub-groups based on family, range size, biogeographic affinity, and host-plant specialization. We recorded 3603 individuals and 253 species of butterflies after the completion of 1860 point counts. Overall, species richness in the majority of the sub-groups (except for Riodinidae and Palearctic species) declines with elevation, as does the density of almost all the sub-groups. From a selection of environmental factors, annual actual evapotranspiration has the strongest effect on the species richness pattern of butterflies as well as on the density of the overall butterfly community, especially the Lycaenidae family. The richness and density of butterfly groups display varied responses to the richness and density of trees and shrubs. The conducive climatic conditions and diverse habitats in the lower valleys of the Eastern Himalaya support a high diversity of butterflies (with majority of small range species) and thus warrants conservation attention.

Highlights

There has been an upsurge in studies assessing biodiversity patterns across broad spatial scales, explaining the underlying processes, and exploring any conservation implications (Stevens 1992, Sánchez-Rodríguez and Baz 1995, Rahbek 2005, Acharya et al 2011a, Wu et al 2013a, Li and Feng 2015, Rana et al 2019, Supriya et al 2019)
This study examines the pattern of species richness and density of butterfly communities along an elevation gradient in Rangeet Valley in Sikkim, Eastern Himalaya, India
The trends in species richness and density and associated biotic, abiotic, and spatial factors vary with the sub-groups considered

Summary

Introduction

There has been an upsurge in studies assessing biodiversity patterns across broad spatial scales, explaining the underlying processes, and exploring any conservation implications (Stevens 1992, Sánchez-Rodríguez and Baz 1995, Rahbek 2005, Acharya et al 2011a, Wu et al 2013a, Li and Feng 2015, Rana et al 2019, Supriya et al 2019). Environmental gradient studies e-ISSN: 1948-6596 https://escholarship.org/uc/fb doi:10.21425/F5FBG49643 Factors such as contemporary climate, habitat heterogeneity, evolutionary events, and area or space have been proposed to explain diversity patterns along elevational gradients (Wiens et al 2007, McCain and Grytnes 2010). The climatic factors include temperature, precipitation, humidity, and cloud cover (Rosenzweig 1992, Sánchez-Rodríguez and Baz 1995, Despland et al 2012) These factors regulate the productivity and water-energy dynamics of mountainous ecosystems (O’Brien 2006, Wu et al 2013b, Hu et al 2017, Vetaas et al 2019). Taxon or regionally specific studies need to be conducted so as to develop more specialized models

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