Variation in species richness of plants and diverse groups of invertebrates in three calcareous grasslands of the Swiss Jura mountains

Abstract

Species richness and abundance of vascular plants and several groups of invertebrates (spiders, oribatid mites, diplopods, grasshoppers and bush crickets, ground beetles, butterflies and terrestrial gastropods) were recorded in three calcareous grasslands (Nenzlingen, Movelier and Vicques) in the northwestern Swiss Jura mountains. Species richness varied both between taxonomical groups and between sites (species richness ranges: 96-116 vascular plants, 60-66 spiders, 18 oribatid mites at each site, 1-7 diplopods, 10-16 grasshoppers and bush crickets, 19-21 ground beetles, 32-46 butterflies and 15-21 terrestrial gastropods). Species overlap (number of species that occured at all sites) was relatively large in terrestrial gastropods (59,1%), butterflies (56,5%), vascular plants (53,8%) and gasshoppers (47,1%), but relatively low in oribatid mites (32,3%), spiders (25,0%), ground beetles (18,4%) and diplopods (12,5%). Diversity expressed by the Shannon-Wiener index (H') was compared for five groups of invertebrates. Diversity was largest in spiders and ground beetles and lowest in terrestrial gastropods. Different taxonomical groups had their maximum diversity at different sites: each grassland had the highest diversity in a least one groupe. The three sites also varied in the abundance of different invertebrate groups. Most groups had the highest densities in Nenzlingen and the lowest densities in Vicques. All three sites contained a high proportion of species listed in the Red Data Book of Switzerland with values averaging 49,5% in grasshoppers and buch crickets, 28,9% in butterflies, 18,9% in vascular plants, 11,2% in terrestrial gastropods, and 6,7% in ground beetles. One spieder species (Oxyptila pullata) and two mite species (Epilohmannia cylindrica minima and Pergalumna myrmophila) were recorded for the first time in Switzerland.