Urban soil compaction reduces cicada diversity

Abstract

[Introduction]Urbanization converts animal habitats into globally homogeneous environments. Consequently, urban communities have low diversity and are often dominated by a few species. However, proximate environmental factor(s) causing community degradation have rarely been identified among diverse and co-varying urban parameters. [Results]The present study addresses the recent loss of cicada diversity in Osaka, Japan, where cicada communities are overwhelmed by a single species, Cryptotympana facialis. A field survey across an urban-forest gradient revealed that the trend of decreasing cicada diversity toward the urban core was mostly associated with the soil hardness among the environmental variables examined. Simultaneously, the proportion of C. facialis increased with soil hardness, although this effect was partially mitigated in forest patches. Newly hatched nymphs of C. facialis exhibited greater burrowing ability than that in other native species. [Conclusions]These findings identify soil compaction due to urbanization as a possible cause of cicada diversity loss, as it impedes the passage of nymphs to underground nests. This impact of urban soil compaction may influence ecosystem functioning of soil-dwelling arthropods and their trophically associated animals.