Forest fragmentation and defaunation are considered the main drivers of biodiversity loss, yet the synergistic effects of landscape changes and biotic interactions on assemblage structure have been ...poorly investigated. Here, we use an extensive dataset of 283 assemblages and 105 species of small mammals to understand how defaunation of medium and large mammals and forest fragmentation change the community composition and diversity of rodents and marsupials in tropical forests of South America. We used structured equation models to investigate the relationship between small mammal species, functional and phylogenetic diversity with forest size, forest cover and the occurrence of medium and large mammals. The best‐fit model showed that defaunation reduced functional diversity, and that species diversity of small mammals increased with forest patch size. Forest cover did not affect functional and phylogenetic diversity. Our results indicate that occurrence of medium and large sized mammals (probably acting as predators, or competitors of small mammals) and forest patch size help to retain species and functional diversity in small mammal communities. Further, the number of species in a small mammal community was critical to the maintenance of phylogenetic diversity, and may have a pronounced influence on the ecological functions played by small mammals. Identifying how phylogenetic and functional diversity change in function of human pressures allows us to better understand the contribution of extant lineages to ecosystem functioning in tropical forests.
Abstract
Figs
(Ficus spp.)
has important roles in an ecosystem, for instance as food source for frugivorous, especially birds. The aims of this study were to determine species richness of bird that ...commonly visited Ficus trees in Ungaran mountain area and analyze their behaviour in dietary among fig visitors. This study used observatory method. Based on preliminary observation, we determined eight species of Ficus tree as samples to be observed according to fruit size and its availability during study. Observations were conducted at 6 - 10 am and 3 - 5 pm. Based on the results, we found 29 species of birds from 16 families and one mammal species who visited Fig trees. The observations showed four different bird activities: only perched, eating fig, eating insects, and eating fruit and insects. Ordination analysis resulted that inter-specific interactions among figs frugivorous tend to use niche partitioning mechanism based on different arrival time and canopy position. This mechanism minimizes the occurrence of competition in obtaining similar resources.
Abstract
Introduction
Glutamate concentrations in the cortex fluctuate with the sleep wake cycle in both rodents and humans. Altered glutamatergic signaling, as well as the early life onset of sleep ...disturbances have been implicated in neurodevelopmental disorders such as autism spectrum disorder. In order to study how sleep modulates glutamate activity in brain regions relevant to social behavior and development, we disrupted sleep in the socially monogamous prairie vole (Microtus ochrogaster) rodent species and quantified markers of glutamate neurotransmission within the prefrontal cortex, an area of the brain responsible for advanced cognition and complex social behaviors.
Methods
Male and female prairie voles were sleep disrupted using an orbital shaker to deliver automated gentle cage agitation at continuous intervals. Sleep was measured using EEG/EMG signals and paired with real time glutamate concentrations in the prefrontal cortex using an amperometric glutamate biosensor. This same method of sleep disruption was applied early in development (postnatal days 14–21) and the long term effects on brain development were quantified by examining glutamatergic synapses in adulthood.
Results
Consistent with previous research in rats, glutamate concentration in the prefrontal cortex increased during periods of wake in the prairie vole. Sleep disruption using the orbital shaker method resulted in brief cortical arousals and reduced time in REM sleep. When applied during development, early life sleep disruption resulted in long-term changes in both pre- and post-synaptic components of glutamatergic synapses in the prairie vole prefrontal cortex including increased density of immature spines.
Conclusion
In the prairie vole rodent model, sleep disruption on an orbital shaker produces a sleep, behavioral, and neurological phenotype that mirrors aspects of autism spectrum disorder including altered features of excitatory neurotransmission within the prefrontal cortex. Studies using this method of sleep disruption combined with real time biosensors for excitatory neurotransmitters will enhance our understanding of modifiable risk factors, such as sleep, that contribute to the altered development of glutamatergic synapses in the brain and their relationship to social behavior.
Support (if any)
NSF #1926818, VA CDA #IK2 BX002712, Portland VA Research Foundation, NIH NHLBI 5T32HL083808-10, VA Merit Review #I01BX001643
The beta-null deviation measure, developed as a null model for beta-diversity, is increasingly used in empirical studies to detect the underlying structuring mechanisms in communities (e.g. niche ...versus neutral and stochastic versus deterministic). Despite growing use, the ecological interpretation of the presence/absence and abundance-based versions of the beta-null diversity measure have not been tested against communities with known assembly mechanisms, and thus have not been validated as an appropriate tool for inferring assembly mechanisms. Using a mechanistic model with known assembly mechanisms, we simulated replicate metacommunities and examined beta-null deviation values 1) across a gradient of niche (species-sorting) to neutrally structured metacommunities, 2) through time, and 3) we compared the effect of changes in assembly mechanism on the performance of the beta-null deviation measures. The impact of stochasticity on assembly outcomes was also considered. beta-null deviation measures proved to be interpretable as a measure of niche or neutral assembly. However, the presence/absence version of the beta-null deviation measure could not differentiate between niche and neutral metacommunities if demographic stochasticity were present. The abundance-based beta-null deviation measure was successful in distinguishing between niche and neutral metacommunities and was robust to the presence of stochasticity, changes through time, and changing assembly mechanisms. However, we suggest that it is not robust to changing abundance evenness distributions or sampling of communities, and so its interpretation still requires some care. We encourage the testing of the assumptions behind null models for ecology and care in their application.
The hexadehydro-Diels-Alder reaction HOYE, Thomas R; BAIRE, Beeraiah; DAWEN NIU ...
Nature (London),
10/2012, Volume:
490, Issue:
7419
Journal Article
Peer reviewed
Open access
Arynes (aromatic systems containing, formally, a carbon-carbon triple bond) are among the most versatile of all reactive intermediates in organic chemistry. They can be 'trapped' to give products ...that are used as pharmaceuticals, agrochemicals, dyes, polymers and other fine chemicals. Here we explore a strategy that unites the de novo generation of benzynes-through a hexadehydro-Diels-Alder reaction-with their in situ elaboration into structurally complex benzenoid products. In the hexadehydro-Diels-Alder reaction, a 1,3-diyne is engaged in a 4+2 cycloisomerization with a 'diynophile' to produce the highly reactive benzyne intermediate. The reaction conditions for this simple, thermal transformation are notable for being free of metals and reagents. The subsequent and highly efficient trapping reactions increase the power of the overall process. Finally, we provide examples of how this de novo benzyne generation approach allows new modes of intrinsic reactivity to be revealed.
Aim: Predators often have important roles in structuring ecosystems via their effects on each other and on prey populations. However, these effects may be altered in the presence of anthropogenic ...food resources, fuelling debate about whether the availability of such resources could alter the ecological role of predators. Here, we review the extent to which human-provided foods are utilised by terrestrial mammalian predators (> 1 kg) across the globe. We also assess whether these resources have a direct impact on the ecology and behaviour of predators and an indirect impact on other co-occurring species. Location: Global. Methods: Data were derived from searches of the published literature. To summarise the data we grouped studies based on the direct and indirect effects of resource subsidies on predators and co-occurring species. We then compared the types of predators accessing these resources by grouping species taxonomically and into the following categories: (1) domesticated species, (2) mesopredators and (3) top predators. Results: Human-provided foods were reported to be utilised by 36 terrestrial predator species in 34 different countries. In the presence of these resources we found that: (1) predator abundance increased, (2) the dietary preferences of predators altered to include the food subsidy, (3) life-history parameters such as survival, reproduction and sociality shifted to the benefit or detriment of the predator, and (4) predators changed their home ranges, activity and movements. In some instances, these modifications indirectly affected co-occurring species via increased predation or competition. Main conclusions: The availability of human-provided food to predators often results in behavioural or population-induced changes to predators and trophic cascades. We conclude that there is an urgent need to reduce the access of predators to food subsidies to minimise human-wildlife conflicts and to preserve the integrity of ecosystem functioning in human-influenced landscapes world-wide.
Competitive exclusion and habitat filtering influence community assembly, but ecologists and evolutionary biologists have not reached consensus on how to quantify patterns that would reveal the ...action of these processes. Currently, at least 22 α‐diversity and 10 β‐diversity metrics of community phylogenetic structure can be combined with nine null models (eight for β‐diversity metrics), providing 278 potentially distinct approaches to test for phylogenetic clustering and overdispersion. Selecting the appropriate approach for a study is daunting. First, we describe similarities among metrics and null models across variance in phylogeny size and shape, species abundance, and species richness. Second, we develop spatially explicit, individual‐based simulations of neutral, competitive exclusion, or habitat filtering community assembly, and quantify the performance (type I and II error rates) of all 278 metric and null model combinations against each assembly process. Many α‐diversity metrics and null models are at least functionally equivalent, reducing the number of truly unique metrics to 12 and the number of unique metric + null model combinations to 72. An even smaller subset of metric and null model combinations showed robust statistical performance. For α‐diversity metrics, phylogenetic diversity and mean nearest taxon distance were best able to detect habitat filtering, while mean pairwise phylogenetic distance‐based metrics were best able to detect competitive exclusion. Overall, β‐diversity metrics tended to have greater power to detect habitat filtering and competitive exclusion than α‐diversity metrics, but had higher type 1 error in some cases. Across both α‐ and β‐diversity metrics, null model selection affected type I error rates more than metric selection. A null model that maintained species richness, and approximately maintained species occurrence frequency and abundance across sites, exhibited low type I and II error rates. This regional null model simulates neutral dispersal of individuals into local communities by sampling from a regional species pool. We introduce a flexible new R package, metricTester, to facilitate robust analyses of method performance.
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