Julio Arroyo

Oribatid mite (Acari) community structure in steppic habitats of Burgos Province, central northern Spain

This work is a study of the communities of oribatid mites in steppic areas of Burgos Province, central northern Spain, in relation to different habitat types belonging to natural or disturbed ecosystems. The primary objective was to find the relationship between anthropogenic use of land and several diversity indices. Parameters such as abundance, species richness, real diversity (H′) and equitability (J′) of the mite communities were calculated in 20 soil plots, sampled in spring and autumn 2000, belonging to the predominant habitat types of this area: (1) cultivated lands, (2) abandoned crop lands, (3) grasslands/pastures, and (4) natural oak forests or a pine plantation. The most widespread species in the area as well as the most abundant taxa overall are documented, together with the faunistic checklist of oribatid mites identified in the study. The results show a general decline in the composition of the oribatid community, in terms of species diversity and abundance, from non‐disturbed soils to cultivated lands. The number of species (richness) was usually higher in forest soils than in disturbed ecosystems, in which the most degraded soils showed the lowest number of species. The community analysis shows the differences due to habitat type and ubiquitous bioindicator species.

Mites occurring in the canopy of Sitka spruce growing in Ireland

Following centuries of deforestation, the area of forest in Ireland is increasing at a rate of between 20,000 and 25,000 hectares annually. However, the vast majority of the afforestation has been with Sitka spruce which is native to North America. In this study we describe the oribatid fauna of a Sitka spruce canopy in Ireland and compare it with the fauna occurring in the canopies of North America. In Ireland, 24 species of Oribatida, representing 20 genera, were recorded from two arboreal microhabitats: canopy (leaves and branches) and epiphytic moss. Two of these species, Malaconothrus (M.) egregius and Ophidiotrichus tectus, were new records for Ireland and the latter was the first record of the genus Ophidiotrichus. Diversity indices and rarefaction curves demonstrate that oribatid mite diversity is greatest in both canopy and epiphyte samples collected at the upper heights. Over 50% of the oribatids recovered from the canopy were Brachypilina and the assemblage was dominated by Phauloppia lucorum and Camisia segnis, with the remainder of the species being poorly represented (except Chamobates schuetzi and Eupelops acromios). Of the 19 species found in the moss, P. lucorum and Zygoribatula exilis were the most abundant taxa, and C. segnis was uncommon. In this microhabitat, 91% of individuals collected were Brachypilina which is not unexpected. Species richness is considerably lower than in similar habitats with native Sitka spruce and arboreal genera, such as Dendrozetes and Scapheremaeus, were not found in this study.