Kris French

ABSTRACT Urbanisation causes significant changes to species composition, species interactions and ecological and evolutionary processes. Changes in host–parasite interactions have the potential to be one of the important consequences of urbanisation, influencing the species able to exploit urban landscapes. We compile information about these less-studied interactions, focusing on the interaction between parasites (ectoparasites, blood parasites and intestinal parasites) and birds. Our review of the literature identified a poor knowledge of bird–parasite interactions in urban areas. While studies identifying parasites were more common than those comparing parasite abundance or host health, studies were limited geographically and to a few bird species. We found that urbanisation could have a positive or negative effect on the diversity and prevalence of bird parasites. Very few studies have linked parasite loads to bird health. We identify some hypotheses that need further consideration across broader regions and species to determine if parasites play a role in the establishment and success of birds in cities and how their health and body condition are affected. Studies of this type could provide valuable tools to understand how to maintain and conserve urban biodiversity.

ABSTRACT AimBiological invasions and anthropogenic habitat modification are considered to be the leading drivers of global environmental change, yet their synergistic impacts on native communities remain poorly understood. We tested the effects of an invasive grass, Stenotaphrum secundatum, on an endangered coastal swamp forest community across an anthropogenic land use gradient. We also investigated the relative importance of landscape versus local community attributes in mediating the effects of S. secundatum invasion on the community. LocationFour hundred kilometres of the coastline of south-eastern Australia. Methods We compared the diversity, composition and recruitment of resident vegetation in 32 invaded and 32 non-invaded forest stands across an anthropogenic land use gradient. Local disturbance and environmental attributes of the forest (e.g. fire severity, litter abundance, canopy openness, vegetation structure) and adjacent landscape matrix (e.g. cover of forest, urban and agricultural land) were measured in detail at each site. ResultsInvasion was associated with substantial local extinctions of native plant species (i.e. 83% fewer species in invaded sites), altered community compositions and an 85% reduction in rates of woody plant recruitment. Local disturbances and environmental attributes of forest stands and adjacent landscape matrix were similar between invaded and native sites. Invasion caused a twofold increase in litter biomass, which we hypothesize is the primary mechanism by which the invader excludes native species. Landscape modification had no effect on the diversity of adjacent swamp forest. There was no interactive effect of landscape modification and invasion on the native community; species losses in response to invasion were high regardless of the condition of the adjacent matrix. Main conclusionsWe show that impacts of non-native species are not dependent on landscape context and, unexpectedly, that invasion by an alien plant poses a greater threat to diversity of endangered swamp forests than modification of the adjacent matrix.