Environmental changes in biodiversity hotspot ecosystems of
South Ecuador: RESPonse and feedback effECTs (FOR2730)

Resumen:

In tropical forests, herbivorous arthropods remove between 7% up to 48% of leaf area, which has forced plants to evolve defense strategies. These strategies influence the palat- ability of leaves. Palatability, which reflects a syndrome of leaf traits, in turn influences both the abundance and the mean body mass not only of particular arthropod taxa but also of the total communities. In this study, we tested two hypotheses: (H1) The abundance of two important chewer guilds (‘leaf chewers’ and ‘rostrum chewers’), dominant components of arthropod communities, is positively related to the palatability of host trees. (H2) Lower pal- atability leads to an increased mean body mass of chewers (Jarman-Bell principle). Arthro- pods were collected by fogging the canopies of 90 tropical trees representing 31 species in three plots at 1000 m and three at 2000 m a.s.l. Palatability was assessed by measuring several ‘leaf traits’ of each host tree and by conducting a feeding trial with the generalist her- bivore Gryllus assimilis (Orthoptera, Gryllidae). Leaf traits provided partial support for H1, as abundance of leaf chewers but not of rostrum chewers was positively affected by the experi- mentally estimated palatability. There was no support for H2 as neither leaf traits nor experi- mentally estimated palatability affected the mean body mass of leaf chewers. The mean body mass of rostrum chewers was positively related to palatability. Thus, leaf traits and experimentally estimated palatability influenced the abundance and mean body mass of chewing arthropods on the community level. However, the data were not consistent with the Jarman-Bell principle. Overall, our results suggest that the palatability of leaves is not among the dominant factors influencing abundance and mean body mass of the community of chewing arthropod herbivores. If other factors, such as the microclimate, predation or fur- ther (a-)biotic interactions are more important has to be analyzed in refined studies.

Resumen:

Biodiversity monitoring is a global need due to environmental degradation and climate change. Birds are often monitored indicators for environmental health because they are easy assessable, fast reacting species, which supply important ecosystem services. But conventional biodiversity monitoring can be timeconsuming, invasive and it often needs trained specialists, thus appropriate alternatives, especially for largescale assessments, like acoustic monitoring are needed. While numerous acoustic indices were generated no studies occur about their ability to reflect conventional alpha-diversity measures such as species richness, abundance, diversity or evenness under complex conditions like a gradient of elevation and degradation. We choose bird communities along an elevation gradient in natural and degraded rainforests in a highdiverse region in the Ecuadorian Andes to investigate the association among five conventional (total abundance, species richness, Shannon Index, evenness, Gini Index) and three acoustic (Acoustic Diversity Index [ADI], Bioacoustic Index [BI], Acoustic Evenness Index [AEI]) alpha-diversity measures. Furthermore, we investigated the influence of higher resolutions (FFT window size, frequency band size) on the acoustic indices. Further, we tested a new acoustic beta-diversity measure. With help of multivariate analyzes we found acoustic diversity measures were not significantly correlated with conventional diversity measures in high-diverse rainforests. The acoustic indices were correlated between another. The values of the acoustic indices increased with higher resolutions and were strongly positively correlated with their next higher resolution. The NMDS of the conventionally assessed bird communities resulted an elevation gradient and a distinct separation between degraded and natural forest communities. The NMDS of the acoustically assessed bird communities resulted no distinct gradients. The conventional and acoustic alpha-diversity measures were not significantly associated with the elevation or habitat type. ADI, BI and AEI seem not appropriate to reflect conventional diversity measures in high-diverse ecosystems, but BI can reflect avian abundance in less diverse ecosystems. Avian acoustic activity was driven by noisy species and not by species richness or abundance. Higher resolutions of the acoustic indices did not resolute acoustic activity more exactly in this case, thus for communities where birds with long or complex calls (relevant for BI) or narrow frequency ranges (relevant for ADI/AEI) are not dominating the acoustic activity the default resolutions of the acoustic indices seem sufficient. Acoustic beta-diversity assessment seems problematic because the analyzes of frequencies does not reflect species turnover among communities due to the reason that several species can occupy the same frequencies with their calls.

Resumen:

National parks are an important tool for conserving biodiversity, particularly in areas of high biodiversity and endemism such as the tropical Andes. However, national parks often face a variety of stressors related to recreation, road construction and illegal extraction of natural resources. Unfortunately, the influence of these stressors for biodiversity is rarely well documented. Cajas National Park in Ecuador is no exception. Despite being traversed by the Cuenca-Molleturo-Naranjal road, effects of the road construction on biodiversity have not been determined. We therefore assessed the influence of road proximity on bird species richness and abundance as well as composition of bird habitat groups in Cajas National Park using transect walks at 25 m and 250 m distance to the road (overall 18 transects, each 1 km length). In total, we recorded 1110 individuals of 28 páramo bird species. Overall species richness did not differ between transects near and far from the road. Nevertheless, the average abundance of shrubby páramo species was significantly higher far from the road than near the road (Far = 36, Near = 25). Moreover, we found a tendency towards differences in the composition of bird habitat groups between transects near and far from the road. One aspect potentially driving the observed patterns was the increasing proportion of planted non-native woody tree species within páramo grassland near the road, which may have caused reduced abundances of shrubby páramo bird species there. While roads represented a clear impact on the composition of bird species in the páramo, the major effect seems to be driven by the introduction of non- native plant species along the roadside. In order to reduce the impact of roads to a minimum, we suggest that park managers should control the introduction of such plant species.