Do carabids (Coleoptera: Carabidae) and chironomids (Diptera: Chironomidae) exhibit similar diversity and distributional patterns along a spatio-temporal gradient on a glacier foreland?

Abstract

Carabid beetles and chironomid midges are two dominant cold-adapted taxa, respectively on glacier forefiel terrains and in glacialstream rivers. Although their sensitivity to high altitude climate warming is well known, no studies compare the species assemblages exhibited in glacial systems. Our study compares diversity and distributional patterns of carabids and chironomids in the foreland of the receding Amola glacier in central-eastern Italian Alps. Carabids were sampled by pitfall traps; chironomids by kick sampling in sites located at the same distance from the glacier as the terrestrial ones. The distance from the glacier front was considered as a proxy for time since deglaciation since these variables are positively correlated. We tested if the distance from the glacier front affects: i) the species richness; ii) taxonomic diversity; and iii) species turnover. Carabid species richness and taxonomic diversity increased positively from recently deglaciated sites (those ca. 160 m from the glacier front) to sites deglaciated more than 160 yrs ago (those located >1300 m from glacier front). Species distributions along the glacier foreland were characterized by mutually exclusive species. Conversely, no pattern in chironomid species richness and turnover was observed. Interestingly, taxonomic diversity increased significantly: closely related species were found near the glacier front, while the most taxonomically diverse species assemblages were found distant from the glacier front. Increasing glacial retreat differently affect epigeic and aquatic insect taxa: carabids respond faster to glacier retreat than do chironomids, at least in species richness and species turnover patterns.

How do macroinvertebrate communities respond to declining glacial influence in the Southern Alps?

“…As documented for other stream ecosystems in the Alps (Lods-Crozet et al, 2001;Lencioni & Gobbi, 2018;Scotti et al, 2019), kryal sites were dominated by chironomids, representing up to 100 % of the macroinvertebrate fauna at two sites (AG1 and CR0). However, the percentage of chironomids decreased with decreasing glacial influence, and with increasing channel stability, water temperature, and food availability (e.g.…”

“…The quantitative faunal data, expressed as total invertebrate density (ind/m 2 ) per sample (site × season), were [log (x+1)] transformed prior to classification and ordination analyses for normalisation. A cluster analysis (paired group -UPGMA), based on the Bray-Curtis similarity coefficient, was performed to highlight similarities among sites in relation to the macroinvertebrate community (Sneath & Sokal, 1973;Lencioni et al, 2018). Furthermore, a distance-based redundancy analysis db(RDA) was performed to investigate the relationships between fauna and environmental conditions.…”

Recent advances in the study of Chironomidae: An overview

“…two papers addressed the focal issue of climate and environmental changes. the effects of global warming and glacier retreating were evaluated by Lencioni and Gobbi (2018) in a glacier foreland in the italian alps. they demonstrated that increasing glacial retreat differently affect epigeic and aquatic insect taxa: carabid beetles respond faster to glacier retreat than do chironomids, at least in patterns of species richness and species turnover.…”