Environmental correlates of darkling beetle population size (Col. Tenebrionidae) on the Cañadas of Teide in Tenerife (Canary Islands)

The seasonal and yearly patterns in the adult population sizes of the darkling beetle Pimelia radula ascendens (Col. Tenebrionidae) were analysed in relation to climatic and biotic variables in a montane arid ecosystem of Tenerife. Pitfall trapping was conducted from 1988 to 2000, and capture–recapture technique and the Jolly–Seber method were used to estimate population sizes. The population had a long activity period, with seasonal patterns of activity from April to October. Activity densities and population sizes showed a similar seasonal pattern each year, reaching values of more than 13,000 individuals ha−1during the summer and decreasing to 2000 per hectare before diapause. Minimum temperature is positively correlated to population size but not with activity density. During summer, darkling beetles showed a greater increase in population size than in activity density due to lower capture and recapture rates. Pimelia radula ascendens was the most abundant darkling beetle and their population size remained relatively stable over the study period, likely due to the absence of predation and competition, and to the environmental stability.