Movement and ranging patterns of a tropical rat (Leopoldamys sabanus) in logged and unlogged rain forests

Knowledge of how animals move through the environment is important for predicting effects of habitat change on faunal distributions. Logging of tropical rain forests produces habitat changes on multiple scales that may affect movement and habitat use by small mammals. To explore the effects of such habitat changes, we compared movement and ranging patterns of the long-tailed giant rat (Leopoldamys sabanus) in logged and unlogged rain forests in Borneo. On a small scale, movement was quantified using spool-and-line tracks; on a larger scale, movement was quantified via radiotracking. At the small scale, paths (49 tracks of 55.2 m ± 20.7 SD each) were relatively straight, with similar step (straight-line section) length distributions in both forest types. At the larger scale, the rats (16 individuals tracked for 4 nights each, X̄ = 1,443 ± 991 m of movement per night) moved with similar speed through both forest types (mean distance covered per 10-min interval = 32 ± 45 m). Based on telemetry data, mean nightly activity periods for individual rats averaged 485 ±109 min (areas covered = 2,083–9,829 m2), with no statistically significant differences between logged and unlogged forests. The large variability in individual movement parameters was not predicted by sex or forest type, suggesting that the paths taken were most likely responses to the local distribution of resources in a heterogeneous rain-forest environment. We conclude that the logged and unlogged forests did not differ with respect to features that are important to movement and ranging patterns of L. sabanus, suggesting that general differences associated with logging may not predict the effects of this type of disturbance on habitat use by individual species of small mammals.Konstans Wells, Elisabeth K. V. Kalko, Maklarin B. Lakim, Martin Pfeiffe

Bat echolocation calls: adaptation and convergent evolution

Bat echolocation calls provide remarkable examples of ‘good design’ through evolution by natural selection. Theory developed from acoustics and sonar engineering permits a strong predictive basis for understanding echolocation performance. Call features, such as frequency, bandwidth, duration and pulse interval are all related to ecological niche. Recent technological breakthroughs have aided our understanding of adaptive aspects of call design in free-living bats. Stereo videogrammetry, laser scanning of habitat features and acoustic flight path tracking permit reconstruction of the flight paths of echolocating bats relative to obstacles and prey in nature. These methods show that echolocation calls are among the most intense airborne vocalizations produced by animals. Acoustic tracking has clarified how and why bats vary call structure in relation to flight speed. Bats using broadband echolocation calls adjust call design in a range-dependent manner so that nearby obstacles are localized accurately. Recent phylogenetic analyses based on gene sequences show that particular types of echolocation signals have evolved independently in several lineages of bats. Call design is often influenced more by perceptual challenges imposed by the environment than by phylogeny, and provides excellent examples of convergent evolution. Now that whole genome sequences of bats are imminent, understanding the functional genomics of echolocation will become a major challenge

Exploratories for large-scale and long-term functional biodiversity research

Current changes in biodiversity and their functional consequences for ecosystem processes matter for both fundamental and applied reasons. In most places the most important anthropogenic determinant of biodiversity is land use. The effects of type and intensity of land use are modulated by climate and atmospheric change, nutrient deposition and pollution and by feedback effects of changed biological processes. However, it is not known whether the genetic and species diversity of different taxa responds to land-use change in similar ways. Moreover, consequences of changing diversity for ecosystem processes have almost exclusively been studied in model experiments of limited scope. Clearly, there is an urgent scientific and societal demand to investigate the relationships between land use, biodiversity and ecosystem processes in many replicate study sites in the context of actual landscapes. Furthermore, these studies need to be set up in long-term frameworks. Moreover, because monitoring and comparative observation cannot unravel causal mechanisms they need to be complemented by manipulative experiments. In the ‘Exploratories for large-scale and long-term functional biodiversity research’ (see http://www.biodiversity-exploratories.de), we provide a platform for such successful long-term biodiversity research. The biodiversity exploratories aim at contributing to a better understanding of causal relationships affecting diversity patterns and their change, developing applied measures in order to mitigate loss of diversity and functionality, integrating a strong research community to its full potential, training a new generation of biodiversity explorers, extending the integrated view of functional biodiversity research to society and stimulating long-term ecological research in Germany and globally. Our experience has several implications for long-term ecological research and the LTER network including the necessity of formulating common research questions, establishing a joint database, applying modern tools for meta-analysis or quantitative review and developing standardised experimental and measurement protocols for facilitating future data synthesis

Keystone species in seed dispersal networks are mainly determined by dietary specialization

A central issue in ecology is the definition and identification of keystone species, i.e. species that are relatively more important than others for maintaining community structure and ecosystem functioning. Network theory has been pointed out as a robust theoretical framework to enhance the operationality of the keystone species concept. We used the concept of centrality as a proxy for a species’ relative importance for the structure of seed dispersal networks composed of either frugivorous bats or birds and their food-plants. Centrality was expected to be determined mainly by dietary specialization, but also by body mass and geographic range size. Across 15 Neotropical datasets, only specialized frugivore species reached the highest values of centrality. Furthermore, the centrality of specialized frugivores varied widely within and among networks, whereas that of secondary and opportunistic frugivores was consistently low. A mixed-effects model showed that centrality was best explained by dietary specialization, but not by body mass or range size. Furthermore, the relationship between centrality and those three ecological correlates differed between bat- and bird-fruit networks. Our findings suggest that dietary specialization is key to understand what makes a frugivore species a keystone in seed dispersal networks, and that taxonomic identity also plays a significant role. Specialized frugivores may play a central role in network structuring and ecosystem functioning, which has important implications for conservation and restoration