Effects of tropical forest conversion into anthropic land uses on snake diversity

Author(s)

Gabriella Neves Leal Santos

• Document type: Doctoral Thesis
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
• Defense date: 2023-04-25

Examining board members

Marcio Roberto Costa Martins; Otavio Augusto Vuolo Marques; Márcio Borges Martins; Jean Paul Walter Metzger; Fernando Rodrigues da Silva; Marcus Vinícius Vieira

• Advisor: Marcio Roberto Costa Martins

Abstract

Natural habitat conversion into anthropic land uses is considered the main cause of species loss. Nonetheless, its effects on snake diversity are still poorly understood, including in megadiverse ecosystems such as tropical forests. In this thesis we aim to understand how distinct components of snake diversity (i.e., species, functional and phylogenetic) respond to habitat conversion, considering both the effects of local and landscape processes. We also investigated how landscapes distinctly select snake species by their traits and which traits are selected, as well as the implications of this selection for ecosystem functioning and resilience. For this, we collected data of snake communities in a fragmented area of Mata Atlântica composed of different land uses (silviculture and pasture). We identified that loss of forest cover induced loss of all diversity components, although at different spatial scales. Species diversity increased with the proportion of forest cover and the number of forest patches in the landscape. Similarly, phylogenetic diversity increased with the proportion of forest cover and, unexpectedly, with the proportion of silviculture at the local scale, indicating that snake species with movement restriction and/or habitat specialist are evolutionarily distant. Thus, conservation strategies should consider multiple spatial scales in order to conserve distinct components of snake diversity. Moreover, we also identified that spatial configuration of forest and land use types are the main factors influencing the distribution of snake functional traits in the studied landscapes. The distance among forest patches distinctly selected snake species based on their body size and diet specialization, whereas the type of land use selected snakes by their foraging mode. This organization of snake communities mediated by landscape resulted in potential loss of functioning and resilience of the ecosystems associated with communities dominated by generalist species. Because functional traits (i.e., body size, diet specialization and foraging mode) selected by landscape present standardized ways of measuring, we propose they are considered as functional markers in other studies that aim to understand snake response to environmental disturbances. Therefore, we concluded that forest proportion and proximity among forest patches are two fundamental factors to conserve the distinct components of snake diversity, to allow forest connection for different snake species and to enable the maintenance of ecosystem processes in mosaics of tropical forest and land uses. In practical terms, this highlights the importance of the maintenance of legal reserves and areas of permanent protection in private properties, especially if they form ecological corridors, contributing to ensure the persistence of different snake species and ecosystem processes. (AU)

• FAPESP's process: 17/11478-0 - Snakes diversity in native and eucalyptus forests in Monte Verde region, Camanducaia, MG: subsidies for conservation
• Grantee: Gabriella Neves Leal Santos
• Support Opportunities: Scholarships in Brazil - Doctorate