Revealing an invasive plant-mammal-disease vector system in São Paulo State, Brazil

Abstract

Plant invasions can have wide-ranging ecological impacts at different scales on natural communities, and affect fundamental ecosystem functions for the conservation of ecosystem services. In southeastern Brazil, invasive herbaceous plants, such as white ginger (Hedychium coronarium) and elephant grass (Cenchrus purpureus), can alter the diversity of native species in riparian areas, as well as the distribution and abundance of capybaras (Hydrochoerus hydrochaeris), providing habitat for refuge and rest, and, potentially, food. Capybaras usually carry ticks, including Amblyomma sculptum, the agent of often-fatal Brazilian Spotted Fever (BSF) in people. Thus, invasive plants have the potential to increase the risk of BSF in the invaded areas. However, there is a lack of quantitative and qualitative information describing the intensity of these interactions involving invasive plants, capybaras and ticks. Understanding this dynamics will be fundamental to comprehend the spatio-temporal patterns of tick-borne disease risk in this region. This project's overarching goal is to describe and understand the putative invasive plant-capybara-tick system in the state of São Paulo, which will form the basis of further investigation and forecasting of the human health risks posed by this system and its component species. Our project will be supported by three workshops: two at the University of São Paulo and a final project partner workshop at Durham University. At the start of the project, Workshop 1 will establish a network of researchers, managers of protected areas, members of governmental organizations (Department of Fauna / SP, Secretariat of Health / SP), and postgraduate students. This network will form the basis of a data collection campaign to establish the distribution of invasive plants and capybaras. We will use these distribution data to select sites for tick abundance sampling and camera trap surveys, in paired invaded and uninvaded vegetation, to test whether tick abundance and capybara occupancy is greater in invaded areas. Capybara and tick data will be collected in the second half of the project, after Workshop 2, when we will provide training in camera trap methods to estimate capybara occupancy, initiate a pilot study to confirm evidence of capybara presence from vegetation features in drone images, and finalise tick survey methods. In this second workshop, we will also present and discuss preliminary results to the audience of Workshop 1, and get their perceptions and suggestions. After field data collection and analysis, we will review our key findings in Workshop 3 at the end of the project, discuss lessons learned, incorporate ideas and suggestions received in workshop 2, and develop targeted grant applications to expand the project. Our project will bring together a unique combination of skills and experience of the project partners to form the basis of a long-lasting UK-São Paulo state collaborative network, focused on systems-based research of the human impacts of invasive species. (AU)