Climate change and its impact on epigean and hypogean carabid beetles

Abstract

Background and purpose: The approaches to the impact of climate change on carabid beetles are highly differentiated. We review here most studies that tried to compare past situations with present time conditions that may concern ground beetle species, populations and phenology, area and upslope shifts. Both epigean and hypogean domains have taken in consideration and, whenever possible, all time scales addressed by the authors.

Materials and methods: The methods adopted vary in relation to the time scale. Geo-period studies cover the largest time lapse, and compare Plio-Pleistocene fossil species assemblages with present ones. Further approaches concern long-term observations based on museum materials and the response of carabids to climate or man-conditioned habitat changes. Primarily devoted to the understanding of climate change impacts on communities are the space-for-time and the time-per-time approach, that imply the comparison of year samples collected in the same site after some decades. Other long-term studies are devoted to the phenology changes. The impact on cave dwelling carabids has studied by recording the new taxa discoveries during the last two centuries.

Results: Geo-period studies reveal strong area expansions restrictions or local extinctions of presently living ground beetles. The old idea of a stability of taxonomic status of such beetles seems to give way to a more dynamic vision of speciation events during the Quaternary, as suggested by recent population genetics studies on Trechines and some Carabus species. Long term studies based on museum materials reveal population and area declines of large and brachypterous species of open lands, but the climate responses are difficult to disentangle from anthropogenous habitat and landscape modifications. The space-for-time approach focuses especially glacier forelands but seems promising also in forecasting species declines starting from climate gradients in forests. The time-for-time (time lapse) monitoring of ground beetle assemblages has adopted so far in Mediterranean mountains and Dolomites. It reveals that in the last three decades a strong uphill shift has observed especially in open land assemblages. In the Dolomites local extinctions and decline of species’ diversity has recorded around or above the tree line. The long-term monitoring of carabids in defined habitats provides extremely rich databases that can be useful in explain the relationships between climate change, population decline or increase and species phenology. Hypogean obligate troglobitic carabids revealed to be extremely sensitive to global warming, as testified by the continuous appearance of new highly evolved taxa that concentrate in the periods of fastest temperature rise of the last century.

Conclusions: Epigean and hypogean carabid beetles are excellent and “multitask” indicators of climate change. Moreover, their response time to climate changes seems to be shorter than for plants.

Key words: space-for-time monitoring, time-per-time, species decline, extinction, species assemblages, phenology, global warming impact, long-term monitoring