Dissertations, Theses, and Capstone Projects

Date of Degree

9-2021

Document Type

Dissertation

Degree Name

Ph.D.

Program

Biology

Advisor

José D. Anadón

Committee Members

David C. Lahti

Lisa L. Manne

Julie L. Lockwood

José Antonio Sanchez-Zapata

Subject Categories

Biodiversity | Nature and Society Relations | Ornithology | Other Ecology and Evolutionary Biology | Terrestrial and Aquatic Ecology | Zoology

Keywords

Biodiversity, Elevational diversity gradient, Ecosystem services, Ecosystem function, Socioecology, Conservation in South Asia

Abstract

A growing number of studies recognize the ecological significance of vertebrate scavengers, and several species belonging to this diverse, functional guild are of high conservation importance around the globe. Studies on taxonomic and functional components of biodiversity often use elevation gradients to comprehensively examine patterns and drivers across multiple spatial scales. Yet, there are relatively few elevational studies on large vertebrates or multi-taxa guilds, and the related variation of their ecosystem services. In particular, scavenger research has largely focused on local-scale studies or regional/global comparisons of local-scale investigations. Moreover, these studies primarily consider taxonomic community characteristics and the patterns of functional diversity remain understudied for vertebrate scavenger communities.

In this dissertation, I examine the taxonomic and functional characteristics of vertebrate scavenger assemblages along an elevation and biome gradient in the Chitwan-Annapurna landscape of Central Nepal. Specifically, I present an integration of ecological and socioecological approaches, across four chapters, to develop our understanding of how distribution, structure, function and human perception vary in relation to scavengers across a species-rich, heterogeneous landscape. By monitoring 43 vertebrate scavenger assemblages with remote, motion-triggered cameras, I collected data on community characteristics across three main elevation bands (i.e. lowland, midland, highland) of the gradient. Then, I compiled relevant functional trait characteristics for all recorded species to calculate a range of functional diversity measures that were used across all four chapters. In the first section of the dissertation, I characterize the taxonomic and functional patterns of diversity (Chapter 1) and community structure (Chapter 2) across the gradient. I test a selection of leading hypotheses related to biodiversity distribution, and scavenger diversity in specific, to evaluate the effects of elevation, and other biotic or abiotic factors. For both taxonomic and functional components, I found that richness is jointly driven by elevation and human impact, whereas other environmental factors (i.e. canopy cover, annual temperature range) and human impact shape community composition at local assemblages. While elevation played an overarching role in the distribution of richness within each elevation band as a function of human impact, compositional differences between local assemblages were largely a consequence of environmental filtering, characterized by high taxonomic species turnover and functional redundancy.

The latter portion of this dissertation, I focus on the taxonomic and functional characteristics that influence scavengers’ capacity to provide ecosystem functions, and the human-dimension in regard to the perception of these roles across the landscape. I test hypotheses related to the relative contribution of taxonomic and functional trait-based indices on the efficiency of key ecological processes provided by scavengers. I found that carcass detection was influenced by a combination of overall biomass and functional richness, whereas biomass and a greater proportion of carnivores drove carcass consumption rate. Also, I find preliminary evidence of the diversity-stability relationship in a vertebrate scavenging guild, related to the ecosystem function of carcass consumption at assemblages with greater overall biomass and functional richness. Finally, I consider the social perceptions of an important stakeholder in this landscape (i.e. livestock farmers) on the ecosystem service provisioning and functional importance of species in this diverse guild, and assess the influence of sociodemographic traits that may drive these attitudes. I find that farmers only perceive avian scavengers as beneficial ecosystem service providers. However, there was species-specific variation regarding their perception of functional importance. Accordingly, the two responses were coupled for obligate scavengers and decoupled for facultative scavengers that suggests disconnect between the appreciation of ecosystem service and knowledge of ecosystem function for several species (other than vultures) in this guild. Relatedly, I find that affluence-related traits drove positive perceptions of ecosystem service provisioning and local ecological knowledge was related to increased valuation of functional importance. Overall, I highlight the potential role of formal education in shaping positive attitudes towards vertebrate scavengers in this landscape. Correspondingly, I emphasize the need to address latent human-wildlife conflicts that might restrict any perceived value of ecosystem services for facultative scavengers, in spite of environmental education and other forms of local ecological knowledge.

The collective findings in this dissertation provides a deeper understanding of the patterns and mechanisms of diversity and ecosystem services for a unique vertebrate scavenger guild, which occurs in a region and at a landscape-scale that is understudied in existing literature. Through this work I build on our scientific knowledge of scavenger ecology and biodiversity-elevation research for vertebrate guilds. I present novel findings of distribution patterns and underlying processes that shape the diversity and ecosystem function of a critical vertebrate guild in a biodiversity hotspot, and explore the multifaceted socioecological relationship between scavengers and humans. Ultimately, these findings may also help inform the identification of key conservation areas, maintain key ecosystem processes, and facilitate inclusive conservation initiatives within the landscape.

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