Urban mires as hotspots of epigaeic arthropod diversity

Natural habitats are lost and fragmented by urbanization globally, resulting in isolated urban remnants of low biodiversity, devoid of specialist species. This homogenization of the urban landscape can be redressed if urban biodiversity hotspots are identified and conserved. Mires have the potential of being such refuges, since they host many mire specialist species of, e.g. arthropods. Here we investigated twenty pine mires that differed in urbanization level (low, intermediate and high) in southern Finland by evaluating the responses of carabid beetle and spider species and communities to potential landscape (level of urbanization, total mire area) and local (pH of peat, vegetation cover, wood volume) drivers. Pitfall trapping was used to collect the arthropods. We showed that high levels of urbanization have a negative effect on mire arthropod biodiversity. However, urban mire community structure seems not to be very different from rural communities as urban mires are still inhabited by mire specialists. Furthermore, tree-covered parts of urbanized mires can serve as refuges for rare forest specialist species and Sphagnum mosses play an important role in supporting mire species and communities, thus Sphagnum growth should be promoted. We showed that urban mires can be considered urban biodiversity hotspots and their protection should be secured in urban development.