Performance of amphibian and dragonfly larvae in an agro-industrial landscape

Author(s)

Daniel Din Betin Negri

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Biociências (IBIOC/SB)
• Defense date: 2015-07-07

Examining board members

Luís César Schiesari; Carlos Arturo Navas Iannini; Ricardo Jannini Sawaya

• Advisor: Luís César Schiesari

Abstract

The global increase in human population and in per capita consumption patterns has created a strong demand for food, fiber and biofuels that only an industrial model of agricultural production can meet. However, industrial agriculture has serious impacts on biodiversity and on the environment. This thesis aimed at testing the hypothesis that land use and land management for the intensive production of soybeans results in a significant reduction in the performance of freshwater organisms, as indicated by survivorship, growth and/or development. This hypothesis was tested by means of field and lab experiments exposing dragonfly larvae and tadpoles to conditions of temporary ponds distributed across a gradient in environmental degradation comprising cerrado, pastures and sugarcane fields. The performance of dragonfly larvae was significantly influenced by land use and land management. Whereas dragonfly survivorship in cerrado and pastures ranged between 50 and 60%, dragonflies transplanted to soybean fields were rapidly eradicated. The synchrony between pesticide application and temporal patterns in mortality strongly suggests that pesticides are the main driver of environmental change precluding the effective colonization of soybean fields by dragonflies. The performance of tadpoles of Physalaemus cuvieri was also significantly influenced by land use and land management. However, tadpole responses were in general less strong and less consistent than those of dragonflies. Tadpoles transplanted to 10-day old soybean fields (first experiment) and 55-day old soybean fields (second experiment) performed as well or better than tadpoles transplanted to reference sites; in strong contrast, tadpoles transplanted to 50-day old soybean fields (second experiment) suffered 100% mortality. Therefore, specific land management practices mediate P. cuvieri performance along the crop cycle. Pastures were always relatively favorable to tadpole survivorship, growth and development. These results have important implications to our conceptualization of the permeability of the agricultural matrix to aquatic and semiaquatic fauna and, therefore, to the conservation of biodiversity in agroindustrial landscapes. In regards to larval habitat, pastures have shown to be highly permeable to the colonization of tadpoles and dragonflies. In turn, soybean plantations appeared to be impermeable to dragonfly development, but temporally permeable to the development of tadpoles (AU)

• FAPESP's process: 13/19834-9 - Performance of larval amphibians and aquatic insects in agroindustrial landscapes
• Grantee: Daniel Din Betin Negri
• Support Opportunities: Scholarships in Brazil - Master