Accelerating loss and degradation of tropical forests has led to a pressing need to understand the conservation value of remaining forests. Whereas most studies focus on the responses in community ...composition and taxonomic richness, more sensitive responses to habitat degradation are likely to be apparent through changes in the trophic complexity of generalist predators. Food web theory predicts that both trophic position and niche breadth of predators decrease with habitat degradation, with consequences for biotic interactions and ecosystem functioning.
Using a stable isotope approach, we analysed trophic positions and niche breaths of an important guild of top predators: insectivorous bats, in the tropical forests of Sabah, Borneo. We aimed to determine the responses in their trophic ecology across an experimental gradient of forest degradation at different spatial scales.
At the landscape scale, trophic niche breadth contracted substantially (78%) in association with a narrow reduction (26%) in forest cover. However, food chains were longer in ecosystems with lower tree canopies, representative of localised habitat simplification. Marked differences in trophic niche breath of and trophic position between echolocation guilds provided further evidence for inter‐guild niche partitioning within bat assemblages. Overall, the functionally important shifts in trophic pathways discriminated among habitats of varying degrees of degradation more reliably than conventional community descriptors, such as diversity metrics.
Synthesis and applications. This study reveals that habitat quality thresholds—below which we see substantial changes to trophic complexity—are higher than previously considered. Our analysis suggests that patches of forest with cover above 90% should be prioritised for conservation over more highly degraded ecosystems. As these effects were detected after approximately 30 years post‐logging, they likely reflect relatively long‐term responses to forest degradation.
This study reveals that habitat quality thresholds—below which we see substantial changes to trophic ecology—are higher than previously considered for community composition. Our analysis suggests that patches of forest with cover above 90% should be prioritised for conservation over more highly degraded ecosystems. As these effects were detected after approximately 30 years post‐logging, they likely reflect relatively long‐term responses to forest degradation.
Habitat degradation is pervasive across the tropics and is particularly acute in Southeast Asia, with major implications for biodiversity. Much research has addressed the impact of degradation on ...species diversity; however, little is known about how ecological interactions are altered, including those that constitute important ecosystem functions such as consumption of herbivores. To examine how rainforest degradation alters trophic interaction networks, we applied DNA metabarcoding to construct interaction networks linking forest‐dwelling insectivorous bat species and their prey, comparing old‐growth forest and forest degraded by logging in Sabah, Borneo. Individual bats in logged rainforest consumed a lower richness of prey than those in old‐growth forest. As a result, interaction networks in logged forests had a less nested structure. These network structures were associated with reduced network redundancy and thus increased vulnerability to perturbations in logged forests. Our results show how ecological interactions change between old‐growth and logged forests, with potentially negative implications for ecosystem function and network stability.
Four polychrome glass fragments, excavated from tomb KV35 in the Valley of the Kings, attributed to Amenhotep II, were analysed to further investigate the composition and provenance of early Late ...Bronze Age (LBA) glasses. An additional fragment, EA64163, cited by the British Museum as being stylistically analogous to the fragments from KV35, although with a findspot simply recorded as ‘Thebes’, was also analysed. Laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS) analysis was used to analyse multiple colours on the fragments to determine the major element composition, the colouring strategies and to establish provenance using trace element analysis. The resulting data obtained were compared with four polychrome fragments of standard LBA Egyptian composition, excavated from the palace of Amenhotep III at Malkata, previously analysed by scanning electron microscopy with wavelength dispersive spectroscopy (SEM‐WDS). Analysis showed that the glasses excavated from KV35 are standard LBA glass of Egyptian composition and were most likely produced in Egypt during the 18th Dynasty. The fragment EA64163 is a low magnesia, low potash glass comparable with Iron Age composition and therefore should be reconsidered as a later glass. The analysis of glasses excavated from a reliable, early Egyptian context supports the proposition that glass technology for multiple colours was established in Egypt at least as early as 1400 bce.
Logging activities degrade forest habitats across large areas of the tropics, but the impacts on trophic interactions that underpin forest ecosystems are poorly understood. DNA metabarcoding provides ...an invaluable tool to investigate such interactions, allowing analysis at a far greater scale and resolution than has previously been possible. We analysed the diet of the insectivorous fawn leaf-nosed bat
Hipposideros cervinus
across a forest disturbance gradient in Borneo, using a dataset of ecological interactions from an unprecedented number of bat-derived faecal samples. Bats predominantly consumed insects from the orders Lepidoptera, Diptera, Blattodea, and Coleoptera, and the taxonomic composition of their diet remained relatively consistent across sites regardless of logging disturbance. There was little difference in the richness of prey consumed per-bat in each logging treatment, indicating potential resilience of this species to habitat degradation. In fact, bats consumed a high richness of prey items, and intensive sampling is needed to reliably compare feeding ecology over multiple sites. Multiple bioinformatic parameters were used, to assess how they altered our perception of sampling completeness. While parameter choice altered estimates of completeness, a very high sampling effort was always required to detect the entire prey community.
•All 41 fragments taken from the site of Serabit are of Egyptian provenance.•All fragments are standard Late Bronze Age high magnesia plant ash glass, except one fragment which is a unique example of ...natron blue glass applied as decoration to a white plant ash vessel body.•Fragments containing cobalt can be confidently dated to specific Dynasties.•Compositional information in conjunction with stylistic “landmarks” narrow the estimated period of production.
Serabit el-Khâdim, located on the western coast of the Sinai Peninsula, is the site of an ancient turquoise mine established in the early 12th Dynasty (c. 1985 BCE) and active between the 18th and 20th Dynasties (c. 1550–1136 BCE). The temple dedicated to Hathor at Serabit detail the number of offerings made, thereby recording the level of activity at Serabit during each reign. The last offerings were made by Rameses VI (1143–1136 BCE) corresponding with the collapse of the Late Bronze Age before the site was abandoned. 976 glass fragments were given to the Ashmolean Museum by Flinders Petrie following his 1905–6 excavations. 41 fragments from the collection were selected for LA-ICP-MS analysis with the aim of provenancing and dating an unknown collection of glass using composition and available stylistic features to further narrow the date of manufacture and therefore indicate the possible workshop of origin. The analysis showed that all 41 fragments are of Egyptian provenance and of standard Late Bronze Age high magnesia plant ash glass, except one fragment which is a unique example of natron blue glass applied as decoration to a white plant ash vessel body. Subtle compositional differences show that 18th Dynasty plant ash glass, plant ash Ramesside glass and natron Ramesside glass are all present, therefore corresponding with the known Egyptian activity at Serabit.
DNA identification of human remains has a valuable role in the field of forensic science and wider. Although DNA is vital in identification of unknown human remains, post-mortem environmental factors ...can lead to poor molecular preservation. In this respect, focus has been placed on DNA extraction methodologies for hard tissue samples, as these are the longest surviving. Despite decades of research being conducted on DNA extraction methods for bone and teeth, little consensus has been reached as to the best performing. Therefore, the aim of this study was to conduct a thorough systematic literature review to identify potential DNA extraction technique(s) which perform optimally for forensic DNA profiling from hard tissue samples. PRISMA guidelines were used, by which a search strategy was developed. This included identifying databases and discipline specific journals, keywords, and exclusion and inclusion criteria. In total, 175 articles were identified that detailed over 50 different DNA extraction methodologies. Results of the meta-analysis conducted on 41 articles – meeting further inclusion criteria - showed that statistically significant higher DNA profiling success was associated with solid-phase magnetic bead/resin methods. In addition, incorporating a demineralisation pre-step resulted in significantly higher profiling successes. For hard tissue type, bone outperformed teeth, and even though dense cortical femur samples were more frequently used across the studies, profiling success was comparable, and in some cases, higher in cancellous bone samples. Notably, incomplete data sharing resulted in many studies being excluded, thus an emphasis for minimum reporting standards is made. In conclusion, this study identifies strategies that may improve success rates of forensic DNA profiling from hard tissue samples. Finally, continued improvements to current methods can ensure faster times to resolution and restoring the identity of those who died in obscurity.
•Systematic literature review on DNA extraction for hard tissue samples.•Demineralisation pre-treatment significantly improved DNA yields.•Solid-phase magnetic bead extraction was associated with the highest DNA profiling success.•Bone samples outperformed teeth samples for DNA yield and profiling success.•Cancellous bone yielded more DNA compared to dense cortical bone.
Human activities, especially conversion and degradation of habitats, are causing global biodiversity declines. How local ecological assemblages are responding is less clear--a concern given their ...importance for many ecosystem functions and services. We analysed a terrestrial assemblage database of unprecedented geographic and taxonomic coverage to quantify local biodiversity responses to land use and related changes. Here we show that in the worst-affected habitats, these pressures reduce within-sample species richness by an average of 76.5%, total abundance by 39.5% and rarefaction-based richness by 40.3%. We estimate that, globally, these pressures have already slightly reduced average within-sample richness (by 13.6%), total abundance (10.7%) and rarefaction-based richness (8.1%), with changes showing marked spatial variation. Rapid further losses are predicted under a business-as-usual land-use scenario; within-sample richness is projected to fall by a further 3.4% globally by 2100, with losses concentrated in biodiverse but economically poor countries. Strong mitigation can deliver much more positive biodiversity changes (up to a 1.9% average increase) that are less strongly related to countries' socioeconomic status.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK
In Southeast Asia, biodiversity-rich forests are being extensively logged and converted to oil palm monocultures. Although the impacts of these changes on biodiversity are largely well documented, we ...know addition to samples we collected in 201 little about how these large-scale impacts affect freshwater trophic ecology. We used stable isotope analyses (SIA) to determine the impacts of land-use changes on the relative contribution of allochthonous and autochthonous basal resources in 19 stream food webs. We also applied compoundspecific SIA and bulk-SIA to determine the trophic position of fish apex predators and mesopredators (invertivores and omnivores). There was no difference in the contribution of autochthonous resources in either consumer group (70–82%) among streams with different landuse type. There was no change in trophic position for meso-predators, but trophic position decreased significantly for apex predators in oil palm plantation streams compared to forest streams. This change in maximum food chain length was due to turnover in identity of the apex predator among land-use types. Disruption of aquatic trophic ecology, through reduction in food chain length and shift in basal resources, may cause significant changes in biodiversity as well as ecosystem functions and services. Understanding this change can help develop more focused priorities for mediating the negative impacts of human activities on freshwater ecosystems.
Despite occupying only 12% of Earth's surface, tropical forests contain disproportionate biodiversity, contribute approximately 40% of terrestrial net primary productivity, and contain 20% of global ...carbon biomass. In parallel, tropical forests experience extreme destruction and degradation, leading to a pressing need to understand the value of degraded forest. Recent work suggests that degraded forests which retain a high percentage of native tree cover, or are in late stage recovery, can support levels of species richness close to those of intact forests. However, the impacts of tropical forest degradation on ecosystem functions remain unclear due to a paucity of studies. Among the key functions that may be modified by habitat degradation is the flux of energy and nutrients through an ecosystem. In chapter two, I determined insectivorous bat community response to short- and long-term pressures, climatic and logging respectively. In the second and third chapters. In the third and fourth chapters I examined how forest degradation influenced bat resource use, food web structure, and associated ecological functions. I focused on summarising complex interactions between bats, their prey and basal resources by analysing naturally abundant isotope compositions. Initially, I focused on shifts across a narrow degradation gradient, and found that both landscape- and localscale traits correlated with changes to isotopic niche and trophic position, respectively. I extended this investigation to examine patterns across both logged and primary forest, and examined how long term habitat changes correlated with dietary shift. Furthermore, I explored how short-term environmental stress interacted with established gradients of habitat quality. In the last chapter, I undertook a 15nitrogen-tracer mesocosms study to investigate dung beetle effects upon nitrogen cycling in tropical soils, facilitating future studies on the response of nitrogen processes to environmental change. This research assists in identification of landscape elements which should be favoured by management policies in order to retain ecosystem functioning.
Baited pitfall traps (BPTs) and flight intercept traps (FITs) are the most common methods employed for sampling dung beetle communities. These methods vary in their efficacy and are affected by ...factors such as the bait types used and the dispersal abilities of different dung beetle species. We present the first quantitative comparison of the community composition, taxonomic and functional diversity of dung beetles caught in human dung BPTs and FITs in Bornean tropical forests. Functional diversity metrics were calculated based on the three functional traits of nesting method, body length, and diel activity. We show that BPTs and FITs captured complementary communities with different functional traits, and that BPTs captured more functionally diverse communities. We therefore recommend using a combination of both BPTs and FITs for studies assessing the composition of dung beetles across habitat types. Our results also highlight that it is important to consider how trap type affects the trait composition of communities when relating dung beetle communities and functional traits to ecological functioning. We suggest modifications to FITs based on the design of harp traps to increase their effectiveness in capturing larger‐bodied beetles.
Through quantitative comparisons, we demonstrated that baited pitfall traps and flight interception traps captured complementary dung beetle communities with different functional traits.
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