Soil arthropods in extreme environments: biodiversity and community structure in the Ansanto Valley (Mefite, Southern Italy)

Soil arthropods play key roles in ecosystem functioning and can be used to detect the impact of environment alterations. The Mefite Geological Site (Campania, Southern Italy) hosts a sulphurous lake, a rare geological phenomenon of gaseous exhalations in a non-volcanic land that affects the vegetation cover in the vast 3km radius. The aim of this study was to characterise the response of soil arthropod community to this extreme condition, underlining its bioindicator role as well as the taxa that can cope with this environment. Arthropods were extracted from soil cores sampled (by Kempson extractor) at 3 distances from the lake: A) 30m, B) 80m and C) 120m away and identified at order level (with a focus on Collembola families, and Protura genera). Community structure (with PERMANOVA based on Bray-Curtis dissimilarity) and taxa associations (with Indicator Species Analysis), Shannon and Simpson biodiversity, and QBS-ar (based on the number of groups morphologically well adapted to soil; PARISI, 2005)(with Mann-Whitney test) were evaluated to understand the extent of the impact of the sulphurous emissions on soil arthropods. Arthropod community composition at order level, as well as QBS-ar index, differ both in A and B compared to C, and the poorest soil biodiversity was found in A. No orders were particularly associated with A, while Acarina and Coleoptera were linked to B and C, and Tetramerocerata was associated to C. Collembola did not show a significant difference in family composition between the different distances from the lake, however Hypogastruridae resulted clearly associated with A. On the other hand, Protura confirmed to be a highly sensitive group, being absent in A and with Acerentulus genera only present in C. Arthropod community composition at order level resulted a sensitive soil bioindicator in sulphurous environments, reflecting soil biological quality (e.g. Tetramerocerata confirmed to prefer more structured soils); however, Collembola showed responses at family level, with Hypogastruridae being tolerant to higher sulphurous environments and Onychiuridae often dominant in the less ones. Proturan’s high sensitivity to disturb is well known, but their presence in Campania is scarcely recorded (first records belong to GALLI, 2021; GALLI and SARÀ, 2022), reporting Acerentulus as the dominant genera, here only present at the major distance from the lake. Firsts records of Acerentomon and Proturentomon in Campania were reported in this study.