Bracken fern (Pteridium aquilinum (L.) Kuhn) overgrowth on dry Alpine grassland impedes Red List Orthoptera but supports local orthopteran beta diversity

Abstract The native bracken fern ( Pteridium aquilinum (L.) Kuhn) has become increasingly invasive in abandoned or undergrazed Alpine grasslands. Bracken stands are generally assumed to be poor species, but there is still very little information about the impact on fauna. We recorded Orthoptera communities of 24 sample plots with varying cover. Compared only sparse medium cover, species richness was highly significantly lower densely overgrown plots, while former two did not differ markedly. Multivariate ordination analyses revealed gradients unequal orthopteran communities, showing distinct patterns cover clustering. Based indicator values, 13 23 turned out marginally associated a single stratum combination strata, whereby all nine Red List were primarily restricted However, some generalist found favor denser stands, such as Tettigonia viridissima , contributing local beta diversity. Our data suggest that ongoing rotational sheep grazing temporary paddocks regarded most preferable management system. selected parts study area, which have vegetation and no pressure scrub overgrowth, recommended alternately left ungrazed for few years allow coexistence different successional stages. Low-intensity control measures, situationally by mowing uprooting, considered appropriate should pursued. Implications insect conservation Even though specialized rare Western Europe tend prefer sparsely vegetated areas, subareas even dense might promote certain leading higher richness.