Urbanisation at multiple scales is associated with larger size and higher fecundity of an orb-weaving spider.

Elizabeth C Lowe,Dieter F Hochuli,Shawn M Wilder,Maura (Gee) G Chapman

doi:10.1371/journal.pone.0105480

Abstract

Urbanisation modifies landscapes at multiple scales, impacting the local climate and changing the extent and quality of natural habitats. These habitat modifications significantly alter species distributions and can result in increased abundance of select species which are able to exploit novel ecosystems. We examined the effect of urbanisation at local and landscape scales on the body size, lipid reserves and ovary weight of Nephila plumipes, an orb weaving spider commonly found in both urban and natural landscapes. Habitat variables at landscape, local and microhabitat scales were integrated to create a series of indexes that quantified the degree of urbanisation at each site. Spider size was negatively associated with vegetation cover at a landscape scale, and positively associated with hard surfaces and anthropogenic disturbance on a local and microhabitat scale. Ovary weight increased in higher socioeconomic areas and was positively associated with hard surfaces and leaf litter at a local scale. The larger size and increased reproductive capacity of N.plumipes in urban areas show that some species benefit from the habitat changes associated with urbanisation. Our results also highlight the importance of incorporating environmental variables from multiple scales when quantifying species responses to landscape modification.

Highlights

Urbanisation modifies landscapes and degrades habitats in order to support increasing human populations in cities around the world [1]
The PCA combining 12 landscape scale variables resulted in four components
Our results show support for our first hypothesis that urbanisation has a positive effect on N.plumipes body size and ovary weight at multiple landscape scales

Summary

Introduction

Urbanisation modifies landscapes and degrades habitats in order to support increasing human populations in cities around the world [1] This alteration of natural areas tends to decrease diversity while increasing densities of select species [2], resulting in biological communities with novel species interactions [3] and altered ecosystem function [4]. In the context of urbanisation, this relates to fragmentation of habitats, increases in housing and population densities and changes to the surrounding land cover from predominantly vegetation to a matrix of hard surfaces, housing, industry and parklands These broad scale increases in impermeable surfaces and decrease in vegetation can lead to changes in climate [13] which, to climate change, have been shown to alter species distributions [14]. Identifying the scale at which anthropogenic changes affect animals can aid in managing the impact of urbanisation on biodiversity and ecosystem health

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Results

Conclusion