Date Published: August 1, 2017
Publisher: Public Library of Science
Author(s): Bernhard Klarner, Helge Winkelmann, Valentyna Krashevska, Mark Maraun, Rahayu Widyastuti, Stefan Scheu, Louis-Felix Bersier.
Conversion of tropical rainforests into plantations fundamentally alters ecological niches of animal species. Generalist predators such as centipedes (Chilopoda) may be able to persist in converted ecosystems due to their ability to adapt and switch to alternative prey populations. We investigated variations in community composition and trophic niches of soil and litter living centipedes in a range of ecosystems including rainforests, jungle rubber agroforests, and rubber and oil palm monocultures in two landscapes in Sumatra, Indonesia. Including information on environmental factors in the soil and litter habitat, we explored drivers shaping ecological niches of soil living invertebrate predators in one of the world’s hotspots of rainforest conversion. Conversion of rainforests into agroforests and plantations was associated with a marked change in the composition of centipede communities. However, irrespective of major differences in habitat characteristics, changes in total abundances were small and the overall diversity and biomass of centipedes was similar in each of the systems investigated, suggesting that the number of ecological niches for this group of predators remains unchanged. By using stable isotope analysis (15N and 13C), we investigated trophic niche shifts of the centipede community; lower δ13C values of centipedes in oil palm plantations as compared to other ecosystems suggests that centipedes switch from decomposer prey to other prey, presumably understory associated herbivores, due to reduced availability of litter associated prey species. The results suggest that the ability to utilize alternative prey is a key feature enabling invertebrate predators to persist in ecosystems undergoing major structural changes due to anthropogenic land use change.
Large areas of tropical forest are logged and converted into cropland, driven by the global demand for commodities such as timber, biofuels and agricultural goods . As a consequence, structurally complex habitats with species rich natural plant and animal communities are progressingly shrinking and making way for landscapes dominated by comparatively monotonous plantations. The intensive management of plantation systems is associated with disturbances such as soil degradation, which have been shown to influence soil animal diversity and biomass, thereby altering and reducing ecosystem services provided by these organisms [2–4]. In South-East Asia logged rainforest sites have been planted in large with rubber (Hevea brasiliensis) and oil palm (Elaeis guineensis), with in particular oil palm gaining importance in the last decades [5,6]. The world’s leading producer country for palm oil and the second ranking producer of natural rubber is Indonesia [7,8]. The Jambi province in Central Sumatra currently is in focus of a large-scale collaborative research project, investigating the ecological functions of natural rainforest and its transformation systems, as well as the human dimensions and economic factors driving the land use change (EFForTS—Ecological and socio-economic functions of tropical lowland rainforest transformation systems; for details see ). Sumatra underwent drastic deforestation in the last decades, with only 30% of its former forests remaining in 2007 . At present the study region is shaped by small-holder and industrial scale rubber and oil palm plantations , but also by remnants of lowland rainforest, thereby providing the opportunity to study consequences of rainforest conversion into agroforestry / agricultural systems in a replicated design.
The number of ecological niches of soil living centipedes in tropical rainforests remains similar even after substantial alteration of the aboveground habitat by conversion of rainforest to plantation systems. Changes in community composition suggest that this is due to euryoecious species replacing rainforest species, but also to the capability of some rainforest species to acclimate to altered conditions in replacement ecosystems by utilizing alternative prey. Identifying these alternative prey groups and developing effective measures to foster generalist predator populations in plantation systems may help in controlling insect pest species thereby contributing to the sustainable management of oil palm and other tropical monoculture plantation systems. Further, conservation measures are needed. A number of rainforest species likely cannot acclimate to conditions in converted systems and are replaced by more common species, which may result in the loss of unique evolutionary lines. The potential loss or weakening of associated ecological functions needs closer investigation. Investigating food web interactions using state-of-the-art techniques such as stable isotope, fatty acid and molecular gut content analysis is key for understanding how changes in community composition alters ecosystem functioning.