One of the more common and dramatic patterns observed in species abundance and richness is that imposed by altitude. Many non-exclusive factors have been proposed to explain these altitudinal patterns, including climate, habitat structure, productivity, geographical factors, and historical factors. In this study, we investigated the altitudinal trend of beetle richness and diversity, trying to determine the factors affecting beetle diversity and composition along an altitudinal gradient on a high mountain of the Sierra Nevada National Park (Spain). Beetles were sampled every 15 d for 2 y using pitfall traps at 10 altitudinal sites located between 2000 and 3000 m asl. Against predictions, beetle diversity and the standardized richness indices were not correlated with altitude. Instead, lower richness and diversity values were found at middle altitude in the selected altitudinal range. Although a combination of biotic and abiotic factors satisfactorily explained these richness and diversity values, the main factor was plant diversity, which was correlated with all richness and diversity indices. A second factor was temperature; however, the interaction between beetle richness and temperature was evident only when the effect of plant diversity was removed. Multivariate analysis for species composition showed that 2 factors, plant diversity and shrub cover, explained more than 50% of the variance observed. In summary, our results suggest a strong dependence of beetle species on vegetation structure and diversity, although temperature appears to be a complementary factor determining beetle richness and diversity in the high mountains of the Sierra Nevada National Park.
Nomenclature: Fauna Europaea Web Service, 2004.