Habitat selection and assemblage structure of darkling beetles (Col. Tenebrionidae) along environmental gradients on the island of Tenerife (Canary Islands)

Relationships between biocoenotic variation trends in the darkling beetle assemblage and several environmental variables of sampling plots at different elevations were investigated at different spatial scales. Classification (UPGMA) and ordination (PCA, CCA) techniques were used to examine these data. Two large groups of species (coastal and mountane) were established, although two clear subgroups (sub-summit and summit) were found in the latter. Likewise, the sub-summit subgroup was divided into a ‘lower-montane’ and ‘middle-montane’. At large scale, several grouping trends showing significant relationships to some climatic factors were observed, principally the height of dew point temperature and the trade wind inversion zones during summer (1200 m a.s.l.) or winter (1600 m a.s.l.). The major trend was conditioned firstly by temperature and secondly by sand content on the soil (xeric habitats). The second trend was influenced by rainfall (moist habitats) and vegetation type. The third trend was opposite to the previous trends. At a fine scale (altitudinal band or stratum), vegetation parameters and edaphic variables were also significant factors (open–closed or sandy–clay microhabitats) as concerns the distribution and abundance of these detritivorous beetles. The observations at different scales reflected different conclusions in the definition of darkling beetle associations and the environmental factors