The pygmy mole cricket Xya variegata as an indicator for dynamic river systems

There is an urgent need to conserve and restore dynamic floodplains as one of the last wildernesses in Europe and to maintain their unique plant and animal communities. Disturbance-dependent ecosystems such as natural floodplains harbour many highly specialised and endangered insect species. One of these species is the pygmy mole cricket Xya variegata Latreille, 1809 (Orthoptera: Tridactylidae), a floodplain specialist of the Ponto-Mediterranean region. However, as with many endangered insect species detailed knowledge on the requirements of X. variegata is largely unknown, even though such knowledge is of particular importance for successful nature conservation. The aim of this study was to analyze the ecological requirements of X. variegata and to verify the species' suitability as an indicator for dynamic river systems of the Ponto-Mediterranean region. Therefore, microhabitat analyses were conducted in August 2010 on 42 plots in a nearly natural floodplain of the western Spanish Pyrenees. The results show that patch occupancy in X. variegata was determined by a high amount of fine sediment particles and low vegetation coverage. Moreover, population sizes were positively correlated with low vegetation and gravel/stone coverage. The plots with the highest population sizes (29 and 36 individuals/0.5 mA(2)) had no vegetation at all. Habitats of X. variegata were usually located distant to the main channel; that is areas where fine sediment particles are deposited after a flood event. Disturbance is thus mandatory for the persistence of the species and makes X. variegata a suitable indicator for dynamic river systems.