Context Matters: Contrasting Ladybird Beetle Responses to Urban Environments across Two US Regions

Monika Egerer,Kevin Li,Theresa Ong

doi:10.3390/su10061829

Abstract

Urban agroecosystems offer an opportunity to investigate the diversity and distribution of organisms that are conserved in city landscapes. This information is not only important for conservation efforts, but also has important implications for sustainable agricultural practices. Associated biodiversity can provide ecosystem services like pollination and pest control, but because organisms may respond differently to the unique environmental filters of specific urban landscapes, it is valuable to compare regions that have different abiotic conditions and urbanization histories. In this study, we compared the abundance and diversity of ladybird beetles within urban gardens in California and Michigan, USA. We asked what species are shared, and what species are unique to urban regions. Moreover, we asked how beetle diversity is influenced by the amount and rate of urbanization surrounding sampled urban gardens. We found that the abundance and diversity of beetles, particularly of unique species, respond in opposite directions to urbanization: ladybirds increased with urbanization in California, but decreased with urbanization in Michigan. We propose that in California water availability in gardens and the urbanization history of the landscape could explain the divergent pattern. Thus, urban context is likely a key contributor to biodiversity within habitats and an important consideration for sustainable agricultural practices in urban agroecosystems.

Highlights

Urbanization is changing biodiversity patterns and population distributions in cities across the world [1,2]
The divergent trend between regions was similar for shared species: shared species abundance, richness and diversity significantly increased in California with greater impervious surface, but were not significant for response measures in Michigan (Table 2)
Unique species abundance significantly increased with impervious cover in California, while unique species abundance significantly decreased in Michigan (Table 2; Figure 2)

Summary

Introduction

Urbanization is changing biodiversity patterns and population distributions in cities across the world [1,2]. Urban environments are characterized by changes in abiotic [3] as well as biotic conditions [4]. Light pollution from buildings and car traffic extends the duration and intensity of light availability, affecting the circadian rhythms of biotic elements [7]. Irrigation of lawns, parks and gardens adds water resources and maintains the presence of vegetation for organisms to exploit [8,9]. The abundance and distribution of species and resources (habitat/food/shelter) in urban areas are often supplemented or altered across time and space [1,10]

Methods

Results

Discussion

Conclusion