Beetle abundance-environment relationships at the Subantarctic-Patagonian transition zone.
ADRIANA, RUGGIERO; SACKMANN, PAULA; FARJI-BRENER, ALEJANDRO G.; MARCELO, KUN
Insect Conservation and Diversity
Lugar: Oxford; Año: 2009 vol. 2 p. 81 - 92
Abstract. 1. The spatial variation in the abundance of individuals may be associatedwith the variation in environmental variables. The productivity hypothesis proposes thatclimate affects plant productivity, which may limit the abundance of beetles. The thermallimitationhypothesis proposes the direct effect of ambient temperature may limit beetleabundance. We analysed the abundance of epigaeic beetles at the SubantarcticPatagoniantransition to test for these abundanceenvironment relationships.2. We collected beetles using 450 pitfall traps within a ~150 × 150 km area representativeof the SubantarcticPatagonian transition. We used path analysis to evaluate therelationships between beetle abundance and plant cover, litter biomass, averaged minimumand daily temperature range, and mean annual precipitation. We used principal coordinatesof neighbour matrices to model the spatial autocorrelation of the data.3. The abundance of beetles increased strongly with tree canopy cover and less stronglywith herb cover. The increase in shrub cover had a positive effect on beetle abundancein areas to the east of the transition, within the scrubland-steppe, but it has a negative effecton beetle abundance in areas to the west of the transition, within the forests. The associationbetween beetle abundance and minimum daily temperature was negative or weakthroughout. Increased temperature variation had a negative effect on beetle abundance.4. We suggest that indirect positive climatic effects mediated through plant cover are importantto account for the variation in beetle abundance, which favours the productivityhypothesis. Thermal limitation may operate locally through variation in daily temperature range.