Urbanization Breaks Up Host-Parasite Interactions: A Case Study on Parasite Community Ecology of Rufous-Bellied Thrushes (Turdus rufiventris) along a Rural-Urban Gradient

Abstract

Urbanization drastically alters natural ecosystems and the structure of their plant and animal communities. Whereas some species cope successfully with these environmental changes, others may go extinct. In the case of parasite communities, the expansion of urban areas has a critical effect by changing the availability of suitable substrates for the eggs or free-larval stages of those species with direct life cycles or for the range of hosts of those species with complex cycles. In this study we investigated the influence of the degree of urbanization and environmental heterogeneity on helminth richness, abundance and community structure of rufous-bellied thrushes (Turdus rufiventris) along a rural-urban gradient in the metropolitan region of Porto Alegre, State of Rio Grande do Sul, Brazil. This common native bird species of southern Brazil hosts 15 endoparasite species at the study region. A total of 144 thrushes were collected with mist nets at 11 sites. The degree of urbanization and environmental heterogeneity were estimated by quantifying five landscape elements: buildings, woodlands, fields, bare lands, and water. Landscape analyses were performed at two spatial scales (10 and 100 ha) taking into account home range size and the potential dispersal distance of thrushes and their prey (intermediate hosts). Mean parasite richness showed an inverse relationship with the degree of urbanization, but a positive relationship with environmental heterogeneity. Changes in the structure of component communities along the rural-urban gradient resulted from responses to the availability of particular landscape elements that are compatible with the parasites' life cycles. We found that the replacement of natural environments with buildings breaks up host-parasite interactions, whereas a higher environmental (substrate) diversity allows the survival of a wider range of intermediate hosts and vectors and their associated parasites.

Urbanisation lowers great tit Parus major breeding success at multiple spatial scales

“…In this study, we chose a single structural component (buildings) rather than multiple (green, grey, blue) components as advocated by Moll et al (2019), driven by the need for a simple metric that could be easily quantified at multiple spatial scales. Similar built-structure urban classifications have been used in many other studies (Coelho et al 2012, Hager et al 2012, Calegaro-Marques and Amato 2014, Vaugoyeau et al 2016; and built-up area correlates strongly with other landcover types across our study plots (Supplementary material Appendix 1). We nevertheless agree with Moll et al (2019) that there is a need to evaluate multiple metrics at multiple scales, but this was not feasible within our study.…”

Does urbanization explain differences in interactions between an insect herbivore and its natural enemies and mutualists?

“…However, there was an indication that parasitized mummies were less frequently found on more urbanized sites of the gradient (closer to the town center, Table 2, model 9), but this factor was not statistically significant. There have been studies which found negative correlations between parasitism and urbanization in a landscape context (Gibb and Hochuli 2002;Bennett and Gratton 2012;Calegaro-Marques and Amato 2014), which was not our objective in this work. The presence of physical barriers and (0) of mummies on the experimental plants.…”

Hierarchical filters determine community assembly of urban species pools

“…). Other trophic interactions can also break down in urban habitats, such as between hosts, parasitoids, and parasites (Nelson and Forbes , Calegaro‐Marques and Amato ), between songbirds and nest predators (Rodewald et al. , Fischer et al.…”