Moorland Beetle Communities on Limestone `Habitat Islands'. II. Flight Activity, and its Influence on Local Staphylinid Diversity

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Abstract
The staphylinid faunas of discrete limestone grassland patches and adjacent blanket peat habitat were studied on two areas of moorland in northern England [UK]. Terrestrial and aerial components of the faunas were sampled using pitfall and window traps, respectively. Two-thirds of all species taken on the Moor House National Nature Reserve were capable of flight. Flight occurred throughout the field season, peaking in late spring and at the end of the summer. Most flight activity occurred in Nomadic species which depend upon flight for the successful exploitation of patchy and transient resources such as sheep dung. Settled species exploiting relatively predictable resources associated with their peat and grassland habitats flew less. Of the Settled species, those living in peat showed least flight activity. In their expansive and continuous habitat flight is not necessary between subpopulations. Limestone species flew more than expected for the relative permanence and stability of their habitat. Flightless species were limited to limestone outcrops large enough to support stable populations. Small colonies of flying species survived by regular dispersal between outcrops, and by receiving airborne immigrants from lowland grasslands to the west. Both flightless and flying Limestone species recorded on the outcrops had a positive species-area relationship consistent with island biogeographical theory. Higher species richness on the larger outcrops is attributed to the positive influences of area per se and to increased habitat heterogenetity. For flying species, the greater interception area presented to immigrants by a larger outcrop may also be a contributing factor. As many as 59% of all staphylinid species recorded at Moor House may have been vagrants carried into the Reserve as aerial plankton, and thus not truly representative of the habitat on which they were taken.