Partition among niche and neutral explanations for metacommunity patterns of fish from Cerrado streams

The Species-Sorting concept, one of the models developed to explain patterns in metacommunity structure, suggests that relationships between biological communities and environmental conditions is the basic means of the species selection processes. A second concept is Neutral Theory, and the idea of neutral dynamics underpinning metacommunity structure, cannot be overlooked. The third mechanism is the Mass-Effect concept, that focuses on the interaction between environmental condition and neutral effects. In the present study, we partitioned fish communities in streams between niche and neutral theory concepts, identifying the best representation of metacommunity structure, and assessed if linear and hydrographic distance were equivalent in the representation of neutral processes. The result points to the importance of species sorting mechanisms in structuring fish communities with neutral processes best represented by the linear distances. These results are important for the fish fauna conservation leading to three considerations: (i) the variation of the landscape and habitat is important for the stream fish, (ii) the natural barriers are an important landscape component to be considered, and (iii) the artificial barriers (dams and impoundments) need to be planned taking in account the catchment basin as the landscape unit.

Background selection theory overestimates effective population size for high mutation rates

Simple models from the neutral theory of molecular evolution are claimed to be flexible enough to incorporate the complex effects of background selection against linked deleterious mutations. Complexities are collapsed into an "effective" population size that specifies neutral genetic diversity. To achieve this, current background selection theory assumes linkage equilibrium among deleterious variants. Data do not support this assumption, nor do theoretical considerations when the genome-wide deleterious mutation is realistically high. We simulate genomes evolving under background selection, allowing the emergence of linkage disequilibria. With realistically high deleterious mutation rates, neutral diversity is much lower than predicted from previous analytical theory.

Variation in the Accuracy of Endpoint Selection in Clinical Studies for Rare Diseases in Respect of Increasing Knowledge on Disease-Severity Measurement

Background: Previous research assessed the accuracy of disease-severity measurement in clinical studies as a mathematical relationship between the set of endpoints selected and the disease-severity scale (DSS), a surrogate for the theoretical Neutral list of indicators representing the disease phenotype. New DSSs are continually developed, so clinical studies’ operationalisation of the Neutral list and resulting relative neutrality may vary over time. We assessed variation in the neutrality of clinical studies over time and the probability of false positive and false negative classifications at different disease prevalence rates.Methods: We used search strings extracted from the Orphanet Register of Rare Diseases using a proprietary algorithm to conduct a systematic review of studies published until January 2021 per Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. Overall, 483 studies and 12 rare diseases met inclusion criteria. We extracted all indicators from clinical studies and calculated neutrality and its components, sensitivity and specificity, as well as the probability of misclassifications at 20%, 50% and 80% disease prevalence rates at two time points, the times of publication of the first and last DSS. Surrogate Neutral lists were the first DSS and a composite of all later DSSs.Results: Over time, the neutrality of clinical studies increased for six diseases and decreased for five diseases, driven by sensitivity for all but Friedreich ataxia. The neutrality of clinical studies in encephalitis decreased, but sensitivity remained constant at zero. At both timepoints, the likely false negative rate increased and the likely false positive rate decreased with increasing disease prevalence. The probability that the least neutral clinical study for most diseases would yield a false positive result was equal to one at all disease prevalence rates. Conclusions: The potential for accurate clinical trial disease-severity measurement increases over time. Neutral theory showed that endpoint selection and DSSs may need improvement in Charcot Marie Tooth disease, Gaucher disease Type I, Huntington’s disease, Sjogren’s syndrome and Tourette syndrome. Using Neutral theory to benchmark disease-severity measurement in rare disease clinical trials may reduce the risk of misclassification, ensuring that recruitment and treatment effect assessment optimise medicine adoption and benefit patients.

The relative abundance of languages: Neutral and non-neutral dynamics

Credible estimates suggest that a large number of the nearly 7000 languages in the world could go extinct this century, a prospect with profound cultural, socioeconomic, and political ramifications. Despite its importance, we still have little predictive theory for language dynamics and richness. Critical to the language extinction problem, however, is to understand the dynamics of the number of speakers of languages, the dynamics of language abundance distributions (LADs). Many regional LADs are very similar to the bell-shaped distributions of relative species abundance predicted by neutral theory in ecology. Using the tenets of neutral theory, here we show that LADs can be understood as an equilibrium or disequilibrium between stochastic rates of origination and extinction of languages. However, neutral theory does not fit some regional LADs, which can be explained if the number of speakers has grown systematically faster in some languages than others, due to cultural factors and other non-neutral processes. Only the LADs of Australia and the United States, deviate from a bell-shaped pattern. These deviations are due to the documented higher, non-equilibrium extinction rates of low-abundance languages in these countries.

Indonesia Languange Utterance by Nias People in Gunung Sitoli

This research aims to find out the factors that influence the pronunciation of Nias people when using Indonesian as a second language, to find out the rules of language change. The theory used in this research is the theory of behaviorism and neutral theory. This research used qualitative research methods and observation techniques to collect data. Data were taken based on interviews with respondents, video recordings of interviews and field notes found in the form of words. The collected data were analyzed using inductive methods and using error analysis techniques to analyze research data. This research interviewed forty five years old man and forty two years woman who are living in Gunung Sitoli. The data collected is related to basic swadesh vocabulary and vocabulary that is not included in swadesh which changes when spoken into Indonesian. The results of the collected data describe and represent the wrong pronunciation when pronouncing Indonesian. The results of this research indicate four factors that influence the change in Nias language in Indonesian. These factors occur because of the differences in the language system of Nias and Indonesian. The use of the Nias language is more dominant than the Indonesian language, the Nias people always use the regional language (Nias) in a formal atmosphere.

Self-consistent migration puts tight constraints on the spatio-temporal organization of species-rich metacommunities

Biodiversity is often attributed to a dynamic equilibrium between immigration of species and competition-driven extinction. This equilibrium forms a common basis for studying ecosystem assembly from a static reservoir of migrants—the mainland. Yet, natural ecosystems often consist of many coupled communities (i.e. metacommunities) and migration occurs between these communities. The pool of migrants then depends on what is sustained in the ecosystem, which in turn depends on the dynamic migrant pool. This chicken-and-egg problem of survival and migration is poorly understood in communities of many competing species, except for the neutral case - the "unified neutral theory of biodiversity". Employing spatio-temporal simulations and mean-field analyses, we show that self-consistent migration puts rather tight constraints on the dynamic migration-extinction equilibrium. When the number of species is large, even weak competitions push species to the edge of their global extinction, such that the overall diversity is highly sensitive to perturbations in demographic parameters, including growth and dispersal rates. When migration is short-range, the resulting spatio-temporal abundance patterns follow broad scale-free distributions that correspond to a directed percolation phase transition. The qualitative agreement of our results for short-range and long-range migration suggests that this self-organization process is a general property of species-rich metacommunities. Our study shows that self-sustaining metacommunities are highly sensitive to environmental change and provides insights into how biodiversity can be rescued and maintained.

Genetic diversity patterns of human ethnic groups as inferred from the 1000 genomes

Human genetic diversity remains to be better understood. We here analyzed data from the 1000 Genomes Project and defined group specific fixed alleles (GSFAs) as those that are likely fixed in one ethnic group but non-fixed in at least one other group. The fraction of derived alleles in GSFAs indicates relative distance to apes because such alleles are absent in apes. Our results show that different groups differed in GSFA numbers consistent with known genetic diversity patterns, but also differed in the fraction of derived alleles in GSFAs throughout the entire genome, with East Asians having the largest fraction, followed by South Asians, Europeans, Native Americans, and Africans. Fast evolving sites such as intergenic regions were enriched with derived alleles and showed greater differences in GSFA numbers between East Asians and Africans. Furthermore, GSFAs in East Asians are mostly not fixed in other groups especially Africans, which was particularly more pronounced for fast evolving noncoding variants, while GSFAs in Africans are mostly also fixed in East Asians. Finally, variants that are likely non-neutral such as those leading to stop codon gain/loss and splice donor/acceptor gain/loss showed patterns similar to those of fast-evolving noncoding variants. These results can be accounted for by the maximum genetic diversity theory but not by the neutral theory or its inference that Eurasians suffered bottlenecks, and have implications for better management of group specific genetic diseases.

Ancient uniparental DNAs in distinguishing the competing theories of molecular evolution and modern human origins

Analyses of extant people have resulted in two models for the uniparental DNA phylogenetic trees of modern humans rooted in either Africa or East Asia. The Africa model is based on the neutral theory. The Asia model is reached from the maximum genetic diversity (MGD) theory. To test the two competing theories, we examined published data of ancient uniparental DNAs. Many ancient samples belonging to a terminal haplogroup were found to have mutated only in some, but not all, of the sites that define a more basal haplogroup. This pattern was found for the non-controversial haplogroups shared by the two competing models, and also for the haplogroups specific to the Asia model. Furthermore, many ancient samples that do not belong to some of the haplogroups of the Africa model nonetheless had mutations in them, which makes it impossible to unambiguously assign them to a haplogroup within the Africa model. Finally, uniparental DNAs of archaic humans were found to carry some modern alleles present in the first uniparental DNAs in the Asia model, indicating convergent evolution. Therefore, the data from ancient DNAs have verified the MGD theory and the actual existence of the haplogroups specific to the Asia model.

Analysing the distance decay of community similarity in river networks using Bayesian methods

The distance decay of community similarity (DDCS) is a pattern that is widely observed in terrestrial and aquatic environments. Niche-based theories argue that species are sorted in space according to their ability to adapt to new environmental conditions. The ecological neutral theory argues that community similarity decays due to ecological drift. The continuum hypothesis provides an intermediate perspective between niche-based theories and the neutral theory, arguing that niche and neutral factors are at the opposite ends of a continuum that ranges from competitive to stochastic exclusion. We assessed the association between niche-based and neutral factors and changes in community similarity measured by Sorensen’s index in riparian plant communities. We assessed the importance of neutral processes using network distances and flow connection and of niche-based processes using Strahler order differences and precipitation differences. We used a hierarchical Bayesian approach to determine which perspective is best supported by the results. We used dataset composed of 338 vegetation censuses from eleven river basins in continental Portugal. We observed that changes in Sorensen indices were associated with network distance, flow connection, Strahler order difference and precipitation difference but to different degrees. The results suggest that community similarity changes are associated with environmental and neutral factors, supporting the continuum hypothesis.

The Dynamic Hypercube as a Niche Community Model

Different models of community dynamics, such as the MacArthur–Wilson theory of island biogeography and Hubbell’s neutral theory, have given us useful insights into the workings of ecological communities. Here, we develop the niche-hypervolume concept of the community into a powerful model of community dynamics. We describe the community’s size through the volume of the hypercube and the dynamics of the populations in it through the fluctuations of the axes of the niche hypercube on different timescales. While the community’s size remains constant, the relative volumes of the niches within it change continuously, thus allowing the populations of different species to rise and fall in a zero-sum fashion. This dynamic hypercube model reproduces several key patterns in communities: lognormal species abundance distributions, 1/f-noise population abundance, multiscale patterns of extinction debt and logarithmic species-time curves. It also provides a powerful framework to explore significant ideas in ecology, such as the drift of ecological communities into evolutionary time.