As much as 80 percent of the world’s biodiversity occurs in tropical forests. The cloud forests of the eastern Andean slopes of Perú are among regions of highest biodiversity and endemism in the world and are seriously threatened by land conversion to agriculture. As climate change becomes more than a prediction, cloud forests are expected to retreat with appropriate habitat shifting to higher elevations, potentially affecting every organism within these highly fragile ecosystems (Pounds 1999). Understanding such changes in biodiversity requires baseline data. In these forests there are no systematic surveys of beetles (Order: Coleoptera), the most diverse taxon on Earth. Ground beetles (Carabidae) are useful biological indicators because they are highly speciose, have low dispersal due to flightless characteristics, and are relatively easy to collect (Niemelä et al. 2000). Although Erwin (1990) studied carabid communities in the Amazon Basin of Perú, no studies have since been conducted on their biodiversity in the highly diverse and imperiled Andean slopes. This study examined carabid beetle diversity along an altitudinal gradient in the tropical montane cloud forests of Perú. Beetles were collected both actively (by hand searches) and passively (by pitfall traps) over a one year period in Manu National Park, southeastern Perú.
Results/Conclusions
We estimate that more than 60% of the 77 morphospecies collected have not yet been described (T. Erwin, pers. comm). There was a mid-altitude peak in species richness, likely due to habitat overlap of high and low elevation species. McCoy (1990) suggests that such results are expected for short-term sampling while a more comprehensive study will reveal peaks in diversity at lower elevations. Seasonality, defined by wet and dry seasons, affected both species number and species composition. Carabid body length was negatively correlated with altitude, probably due to the energetic considerations along an increasing altitudinal gradient. The number of fully winged species was significantly higher at lower altitudes, which we attribute to selection for dispersal ability in the patchy habitat of lowland tropical forests. Recent efforts to inventory insect diversity along an altitudinal gradient have important climatic implications. For example, Chen et al. (2009) found that geometrid moth (Lepidoptera) communities increased 67 m over a 40 year interval in Borneo; the shift in altitudinal zone was most likely due to a changing climate. The present study was the first attempt at an official survey of Carabidae diversity along an elevational gradient in the cloud forests of southeastern Perú.