Abundance, biomass and diversity of ground-beetles (Col. Carabidae) as indicators of climatic change effects over elevation strata in Tenerife (Canary Islands)

Abstract

Species relative importance distribution pattern changes of the ground-beetle assemblages were analyzed along elevation strata of Tenerife Island. The species importance estimates were expressed in terms of (i) activity density, as total catching of ground-beetle adults obtained with pitfall traps over each elevation stratum for one year, and (ii) biomass, as the total number of specimens caught multiplied by a mean dry weight in milligrams for the species. The K-dominance curves indicated moderate or insignificant perturbances, and patterns were sigmoidal following a truncated log-normal slightly skewed to the right, by using the Kolmogoroff–Smirnov test. The results also showed perceptible deviations from the truncated log-normal pattern (p<0.05) mainly with biomass data. The disturbance through successional progress and perturbances by environmental warming and cooling could be assumed by deviations from the log-normal distribution among species. Thus, assuming that the assemblages of strata exhibited generally low similarity, the results will be arranged around the following four tracks: (1) the assemblage progressed toward highest abundances, dominance and a low-diversity equilibrium state in the cloud montane stratum, (2) the assemblage was subject to severe warming and dryness, lowest abundances with dominance in biomass, such that log-normal pattern was not shown in the basal stratum, (3) a non-equilibrium state in summer-xeric montane stratum maintained the highest diversity and an archetypical log-normal pattern was described for assemblage, and (4) assemblage stressed by cold semi-arid climate showed a certain tendency to log-normality and decrease in the diversity for the summit stratum. These results indicate that variation in ground-beetle assemblages by way of advanced evolutionary and adaptive trade-offs can best be understood as consequences of selective pressures by adverse climatic changes – perturbances – or seasonal climatic fluctuations and population dynamics – disturbances – according to the elevation stratum, which can generate different deviations from the log-normal pattern; these are more directly related to magnitude and frequency of local natural disturbance regimes and the productivity of the ecosystem.