Matrix type affects carabid beetle community and trait composition, and intraspecific variation in remnant forests

Abstract

AimThe Anthropocene is characterised by urban and agricultural landscapes. Within these landscapes, natural to semi‐natural habitats are fragmented, isolated and disturbed to varying degrees. Species associated with these natural habitats have to content with the surrounding landscape, both in terms of level of isolation, and matrix type and quality. We investigated the community structure, trait distribution and individual traits of carabid beetles in boreal forest fragments within three matrices: urban, agricultural and freshwater lake.LocationCity of Lahti and its surroundings, southern Finland.TaxonColeoptera, Carabidae.MethodsUsing pitfall traps from June to October 2019, we collected carabid beetles from eight spruce‐dominated forest fragments in the urban matrix, 10 fragments in an agricultural matrix, seven fragments on lake islands and three large control forests at the outskirts of the city.ResultsCompared to natural forests, carabid beetles in forest fragments in these matrices showed distinct assemblages, and with beetle diversity the highest in fragments in the agricultural landscape. Fragments in the urban and lake island landscapes were characterised by small‐sized species, and those capable of flight. We also found strong intraspecific trait responses in terms of body size, with some generalist species being significantly smaller in urban, agricultural or lake island fragments compared to the controls.Main ConclusionsThe matrix has a clear effect on carabid beetle communities, both in terms of taxonomic and trait distribution, and filters for communities of smaller sized species and those capable of flight. Such overall community and intraspecific effects can have considerable effects on populations and community assemblages: As anthropogenic effects intensify in urban and agricultural landscapes, our findings may be the expression of further morphological and physiological responses, and eventually in the adaptation of those species that can cope with the Anthropocene.