Abstract:
Andean mountain rainforests rank among the most diverse ecosystems of the world. Especially for insects these biomes serve as a hotspot. It is still little known about how the extremely species-rich group of moths react to gentle intrusions on naturally grown forests.
The research area of this project (Reserva Biológica San Francisco) is located at the border of the Podocarpus National park in South Ecuador. The research was carried out with moths of the species-rich group of the Arctiidae family, which were collected at 9 sampling sites in ravine forests. Three sampling sites were situated in a branch of a valley with the original undisturbed vegetation, 3 in a branch with lightly disturbed forest vegetation and 3 in a branch with stronger forestral intrusions.
The group of Arctiidae were collected in a period of time between 15.02.2005 and 17.05.2005 using light-traps, that is to say 8-11 month after the completion of the forestral experiment. Light-trapping was carried out at the 9 sampling sites between 19:00 and 22:00 local time using a light trap (with both a 15 W ultra-violet-tube and a normal tube). In 28 nights of sampling 1.054 individuals related to 140 species were caught.
For the final analysis these data were combined with earlier light-trapping data resulting from sampling amongst 4 other habitat types also ranging in elevation from 1.800 m to 2.000 m above sea level (early and late states of succession, open grassland and ridge forest).
In consideration of the abundances of the Arctiidae the 9 locations did not differ from each other nor did the 3 quebradas of the ravine forest. In the ridge forest, the ravine forest and the open grassland far less individuals were collected compared to the succession habitats. The local diversity of the butterfly communities in the ravine forest was not as pronounced as compared to the ridge forest but this might have been caused by seasonal differences and/or the relatively small sample sizes.
The samples of the Arctiidae at all 30 sampling sites were ordained within multidimensional scaling, underlying the CNESS index with the different values of the sampling-parameter m. Thereby a clear segregation of the ravine forest-sites from the ridge forest and the succession-habitats became obvious. The differences between the arctiid faunas became more apparent, if the moderate frequent species were given more weight in the analysis (m = 9-12).
Matrix-rank-correlation-tests with different environmental parameters showed an apparent coherency of the differences in arctiid fauna with the degree of the opening of the crowns (visible sky). Whereas the spatial nearness of the sampling sites to each other did not show any correlation.
The effects of the forestral experiments on the arctiid communities first became apparent when regarding the data from moths collected during the rain period. The community of species of the undisturbed quebrada Q2 clearly differs from the more or less disturbed quebradas. However they do not differ from the structure of the community of the ridge forest. Thus ? disregarding seasonal effects ? the nature forest understorey and ravine forest in the research area do not clearly differ in their fauna. Between the quebradas with different forestral treatments there was no difference in the variety and composition of the species? communities. Abundant species in the disturbed quebrada-forests were Amastus coccinator (2,5%), Areva albogrisea (13%), Melese endopyra (4%) and Napata sp.3 (3,4%).
The sites of the closed nature forest understorey are especially favoured by many monophageous species of the tribe Ctenuchini, whereas in the disturbed habitats sturdy species with stronger flying abilities can be found.
The results of this study show that already small-scale intrusions limited in time on the natural vegetation can cause a significant change in the composition of arctiid communities. At the same time no difference in the impact of the degree of forestral intrusions could be proved.
