Abstract
Simple SummaryUrbanization is an important driver of global change, with negative consequences for biodiversity. Specialist species living in isolated urban forest fragments may be the most impacted by urbanization-driven environmental modifications. We compared various life history parameters of a forest specialist ground beetle in its original forest habitat and in urban forest fragments. Abundance was more than five times higher in the rural forest stands than in the urban forest fragments. We found no significant differences in body size or condition between the rural and urban individuals of either sex. Despite higher temperatures in urban habitats, the beginning of the reproductive period did not start earlier in the urban than the rural habitat. The number of ripe eggs was significantly higher in urban than rural females. The urban environmental conditions, however, seemed to cause high mortality of the immature stages, preventing the growth of urban populations.Urbanization is increasing worldwide and causes substantial changes in environmental parameters, generating various kinds of stress on arthropods, with several harmful consequences. We examined a forest specialist ground beetle, Carabus convexus, in forested habitats to evaluate the changes in four important life history traits between rural and urban populations. Analyzing beetles from the overwintered cohort in their first breeding season, we found no significant differences in body length or body mass between the rural and urban individuals. Body condition, judged by fat reserve scores, was similarly poor in both habitats, indicating that beetles were not able to accumulate substantial fat reserves at either habitat. Females with ripe eggs in their ovaries were first captured at the same time in both areas. The number of ripe eggs, however, was significantly higher in females of the low-density urban population (6.13 eggs/female) than in those of the high-density rural population (4.14 eggs/female), indicating density-dependent fecundity. Altered environmental and habitat conditions by urbanization, however, seemed to cause high mortality during egg hatching and/or larval development, preventing the growth of the urban population to the level of rural one.
Highlights
Anthropogenic activities, including agriculture and urbanization, are important drivers of global change, with negative consequences for biodiversity [1]
We modelled the response variables with count data using a Poisson distribution with log-link function, while the other response variables were analyzed using normal error distribution with log-link function [56]
As neither the body mass nor the body length of rural females or males was significantly different from their urban counterparts, we did not include body mass or length as either a fixed or a random factor in the further generalized linear mixed models (GLMMs) on life history traits
Summary
Anthropogenic activities, including agriculture and urbanization, are important drivers of global change, with negative consequences for biodiversity [1]. Urbanization is a human niche-creating activity, resulting in land take, resource concentration, and modulated environmental and ecological processes, from climatic regimes [5]. Urbanization-related processes cause modifications in habitat structure, composition, and environmental parameters but can result in urban ecological novelties (UEN, [12]). The former may generate various kinds of stress on living organisms (on both vertebrates and invertebrates), with consequences on their activity pattern, spatial distribution, phenology, body condition, fecundity, behaviour, and biotic interactions [2,13,14]. UEN could provide novel resources for urban-dwelling organisms but can lead them into an “ecological trap”, which is a preferred habitat that results in a cost to fitness [15]
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