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

Urbanization can alter the composition of arthropod communities. However, little is known about how urbanization affects ecological interactions. Using experimental colonies of the black bean aphid Aphis fabae Scopoli reared on Vicia faba L, we asked if patterns of predator-prey, host-parasitoid and ant-aphid mutualisms varied along an urbanization gradient across a large town in southern England. We recorded the presence of naturally occurring predators, parasitoid wasps and mutualistic ants together with aphid abundance. We examined how biotic (green areas and plant richness) and abiotic features (impervious surfaces and distance to town center) affected (1) aphid colony size, (2) the likelihood of finding predators, mutualistic ants and aphid mummies (indicating the presence of parasitoids), and (3) how the interplay among these factors affected patterns of parasitoid attack, predator abundance, mutualistic interactions and aphid abundance. The best model to predict aphid abundance was the number of mutualistic ants attending the colonies. Aphid predators responded negatively to both the proportion of impervious surfaces and to the number of mutualistic ants farming the colonies, and positively to aphid population size, whereas parasitized aphids were found in colonies with higher numbers of aphids and ants. The number of mutualistic ants attending was positively associated with aphid colony size and negatively with the number of aphid predators. Our findings suggest that for insect-natural enemy interactions, urbanization may affect some groups, while not influencing others, and that local effects (mutualists, host plant presence) will also be key determinants of how urban ecological communities are formed

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

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

La0.1Ca0.9MnO3/Co3O4 for oxygen reduction and evolution reactions (ORER) in alkaline electrolyte

Non-precious metal bifunctional catalysts are of great interest for metal–air batteries, electrolysis, and regenerative fuel cell systems due to their performance and cost benefits compared to the Pt group metals (PGM). In this work, metal oxides of La0.1Ca0.9MnO3 and nano Co3O47 catalyst as bifunctional catalysts were used in oxygen reduction and evolution reactions (ORER). The catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N2 adsorption isotherms. The electrocatalytic activity of the perovskite-type La0.1Ca0.9MnO3 and Co3O4 catalysts both as single and mixtures of both were assessed in alkaline solutions at room temperature. Electrocatalyst activity, stability, and electrode kinetics were studied using cyclic voltammetry (CV) and rotating disk electrode (RDE). This study shows that the bifunctional performance of the mixed La0.1Ca0.9MnO3 and nano Co3O4 was superior in comparison to either La0.1Ca0.9MnO3 or nano Co3O4 alone for ORER. The improved activity is due to the synergistic effect between the La0.1Ca0.9MnO3 and nano Co3O4 structural and surface properties. This work illustrates that hybridization between these two metal oxides results in the excellent bifunctional oxygen redox activity, stability, and cyclability, leading to a cost-effective application in energy conversion and storage, albeit to the cost of higher catalyst loadings.QC 20180212</p