Boom-bust population dynamics drive rapid genetic change.

Increasing environmental threats and more extreme environmental perturbations place species at risk of population declines, with associated loss of genetic diversity and evolutionary potential. While theory shows that rapid population declines can cause loss of genetic diversity, populations in some environments, like Australia's arid zone, are repeatedly subject to major population fluctuations yet persist and appear able to maintain genetic diversity. Here, we use repeated population sampling over 13 y and genotype-by-sequencing of 1903 individuals to investigate the genetic consequences of repeated population fluctuations in two small mammals in the Australian arid zone. The sandy inland mouse (Pseudomys hermannsburgensis) experiences marked boom-bust population dynamics in response to the highly variable desert environment. We show that heterozygosity levels declined, and population differentiation (FST) increased, during bust periods when populations became small and isolated, but that heterozygosity was rapidly restored during episodic population booms. In contrast, the lesser hairy-footed dunnart (Sminthopsis youngsoni), a desert marsupial that maintains relatively stable population sizes, showed no linear declines in heterozygosity. These results reveal two contrasting ways in which genetic diversity is maintained in highly variable environments. In one species, diversity is conserved through the maintenance of stable population sizes across time. In the other species, diversity is conserved through rapid genetic mixing during population booms that restores heterozygosity lost during population busts.

Widespread chromosomal rearrangements preceded genetic divergence in a monitor lizard, Varanus acanthurus (Varanidae).

Chromosomal rearrangements are often associated with local adaptation and speciation because they suppress recombination, and as a result, rearrangements have been implicated in disrupting gene flow. Although there is strong evidence to suggest that chromosome rearrangements are a factor in genetic isolation of divergent populations, the underlying mechanism remains elusive. Here, we applied an integrative cytogenetics and genomics approach testing whether chromosomal rearrangements are the initial process, or a consequence, of population divergence in the dwarf goanna, Varanus acanthurus. Specifically, we tested whether chromosome rearrangements are indicators of genetic barriers that can be used to identify divergent populations by looking at gene flow within and between populations with rearrangements. We found that gene flow was present between individuals with chromosome rearrangements within populations, but there was no gene flow between populations that had similar chromosome rearrangements. Moreover, we identified a correlation between reduced genetic variation in populations with a higher frequency of homozygous submetacentric individuals. These findings suggest that chromosomal rearrangements were widespread prior to divergence, and because we found populations with higher frequencies of submetacentric chromosomes were associated with lower genetic diversity, this could indicate that polymorphisms within populations are early indicators of genetic drift.

S2k Leitlinie akute infektiöse Gastroenteritis im Säuglings-, Kindes- und Jugendalter ­ Update 2024.

The aim of the interdisciplinary S2k guideline "Acute infectious gastroenteritis in infants, children and adolescents" is to summarise the current state of knowledge on the clinical presentation, diagnosis, treatment, prevention and hygiene of acute infectious gastroenteritis, including nosocomial gastrointestinal infections, in infants, children and adolescents on the basis of scientific evidence, to evaluate it by expert consensus and to derive practice-relevant recommendations from it. The guideline provides a corridor for action for frequent decisions. It also serves the purpose of evidence-based further education and training and is thus intended to improve the medical care of children with acute gastroenteritis. In particular, the guideline aims to avoid unnecessary hospitalisation of children with AGE and to take preventive measures to avoid and spread infection.

Episodic population fragmentation and gene flow reveal a trade-off between heterozygosity and allelic richness.

In episodic environments like deserts, populations of some animal species exhibit irregular fluctuations such that populations are alternately large and connected or small and isolated. Such dynamics are typically driven by periodic resource pulses due, for example, to large but infrequent rainfall events. The repeated population bottlenecks resulting from fragmentation should lower genetic diversity over time, yet species undergoing these fluctuations appear to maintain high levels of genetic diversity. To resolve this apparent paradox, we simulated a metapopulation of constant size undergoing repeat episodes of fragmentation and change in gene flow to mimic outcomes experienced by mammals in an Australian desert. We show that episodic fragmentation and gene flow have contrasting effects on two measures of genetic diversity: heterozygosity and allelic richness. Specifically, fragmentation into many, small subpopulations, coupled with periods of infrequent gene flow, preserves allelic richness at the expense of heterozygosity. In contrast, fragmentation into a few, large subpopulations maintains heterozygosity at the expense of allelic richness. The strength of the trade-off between heterozygosity and allelic richness depends on the amount of gene flow and the frequency of gene flow events. Our results imply that the type of genetic diversity maintained among species living in strongly fluctuating environments will depend on the way populations fragment, with our results highlighting different mechanisms for maintaining allelic richness and heterozygosity in small, fragmented populations.

Polyandry and non-random fertilisation maintain long-term genetic diversity in an isolated island population of adders (Vipera berus).

Conservation genetic theory suggests that small and isolated populations should be subject to reduced genetic diversity i.e., heterozygosity and allelic diversity. Our 34 years study of an isolated island population of adders (Vipera berus) in southern Sweden challenges this notion. Despite a lack of gene flow and a yearly mean estimated reproductive adult population size of only 65 adult adders (range 12-171), the population maintains high levels of heterozygosity and allelic diversity similar to that observed in two mainland populations. Even a 14-year major "bottleneck" i.e., a reduction in adult adder numbers, encompassing at least four adder generations, did not result in any reduction in the island adders' heterozygosity and allelic diversity. Female adders are polyandrous, and fertilisation is non-random, which our empirical data and modelling suggest are underpinning the maintenance of the population's high level of heterozygosity. Our empirical results and subsequent modelling suggest that the positive genetic effects of polyandry in combination with non-random fertilisation, often overlooked in conservation genetic analyses, deserve greater consideration when predicting long-term survival of small and isolated populations.

Large-sample-size assessment of socioeconomic predictors of community-level resource management occurrence.

Community-level resource management efforts are cornerstones in ensuring sustainable use of natural resources. Yet, understanding how community characteristics influence management practices remains contested. With a sample size of ≥725 communities, we assessed the effects of key community (i.e., socioeconomic) characteristics (human population size and density, market integration, and modernization) on the probability of occurrence of fisheries management practices, including gear, species, and spatial restrictions. The study was based in Solomon Islands, a Pacific Island country with a population that is highly dependent on coastal fisheries. People primarily dwell in small communities adjacent to the coastline dispersed across 6 island provinces and numerous smaller islands. We used nationally collected data in binomial logistic regression models to examine the likelihood of management occurrence, given socioeconomic context of communities. In contrast to prevailing views, we identified a positive and statistically significant association between both human population size and market integration and all 3 management practices. Human population density, however, had a statistically significant negative association and modernization a varied and limited association with occurrence of all management practices. Our method offers a way to remotely predict the occurrence of resource management practices based on key socioeconomic characteristics. It could be used to improve understanding of why some communities conduct natural resource management activities when statistical patterns suggest they are not likely to and thus improve understanding of how some communities of people beat the odds despite limited market access and high population density.

Los esfuerzos por manejar los recursos a nivel comunitario son pilares para garantizar el uso sustentable de los recursos naturales. Aun así, el conocimiento sobre cómo las características comunitarias influyen sobre las prácticas de manejo todavía está en discusión. Con un tamaño de muestra de ≥725 comunidades, evaluamos los efectos de las características (tamaño y densidad poblacional humana, integración del mercado y modernización) comunitarias (es decir, socioeconómicas) clave sobre la probabilidad de incidencia de las prácticas de manejo de las pesquerías, incluyendo el equipamiento, las especies y las restricciones espaciales. El estudio se ubicó en las Islas Salomón, un país isleño del Pacífico con una población altamente dependiente de las pesquerías costeras. En este país, las personas habitan principalmente en comunidades pequeñas adyacentes a la costa y dispersas en las seis provincias isleñas y en numerosas islas más pequeñas. Usamos datos recolectados en todo el país en unos modelos de regresión logística binomial para examinar la probabilidad de incidencia del manejo, dado el contexto socioeconómico de las comunidades. Contrario a las opiniones predominantes, identificamos una asociación positiva y estadísticamente significativa entre el tamaño poblacional humano y la integración del mercado y entre las tres prácticas de manejo. La densidad poblacional humana, sin embargo, tuvo una asociación negativa estadísticamente significativa y la modernización una asociación variada y limitada con la incidencia de las prácticas de manejo. Nuestro método ofrece una manera para predecir remotamente la incidencia de las prácticas de manejo de recursos con base en características socioeconómicas importantes. El método podría utilizarse para incrementar el conocimiento sobre cómo algunas comunidades llevan a cabo actividades de manejo de recursos naturales cuando los patrones estadísticos sugieren lo contrario y así mejorar el entendimiento de cómo algunas comunidades humanas superan todos los pronósticos a pesar del acceso limitado al mercado y la alta densidad poblacional. Evaluación de Muestras de Gran Tamaño de Pronosticadores Socioeconómicos de la Incidencia del Manejo de Recursos a Nivel Comunitario.

Genomewide SNP markers breathe new life into phylogeography and species delimitation for the problematic short-necked turtles (Chelidae: Emydura) of eastern Australia.

Understanding the evolutionary history of diversifying lineages and the delineation of evolutionarily significant units and species remains major challenges for evolutionary biology. Low-cost representational sampling of the genome for single nucleotide polymorphisms shows great potential at the temporal scales that are typically the focus of species delimitation and phylogeography. We apply these markers to a case study of a freshwater turtle, Emydura macquarii, whose systematics has so far defied resolution, to bring to light a dynamic system of substantive allopatric lineages diverging on independent evolutionary trajectories, but held back in the process of speciation by low level and episodic exchange of alleles across drainage divides on various timescales. In the context of low-level episodic gene flow, speciation is often reticulate, rather than a bifurcating process. We argue that species delimitation needs to take into account the pattern of ancestry and descent of diverging lineages in allopatry together with the recent and contemporary processes of dispersal and gene flow that retard and obscure that divergence. Underpinned by a strong focus on lineage diagnosability, this combined approach provides a means for addressing the challenges of incompletely isolated populations with uncommon, but recurrent gene flow in studies of species delimitation, a situation likely to be frequently encountered. Taxonomic decisions in cases of allopatry often require subjective judgements. Our strategy, which adds an additional level of objectivity before that subjectivity is applied, reduces the risk of taxonomic inflation that can accompany lineage approaches to species delimitation.

Creating new evolutionary pathways through bioinvasion: the population genetics of brushtail possums in New Zealand.

Rapid increases in global trade and human movement have created novel mixtures of organisms bringing with them the potential to rapidly accelerate the evolution of new forms. The common brushtail possum (Trichosurus vulpecula), introduced into New Zealand from Australia in the 19th century, is one such species having been sourced from multiple populations in its native range. Here, we combine microsatellite DNA- and GIS-based spatial data to show that T. vulpecula originating from at least two different Australian locations exhibit a population structure that is commensurate with their introduction history and which cannot be explained by landscape features alone. Most importantly, we identify a hybrid zone between the two subspecies which appears to function as a barrier to dispersal. When combined with previous genetic, morphological and captive studies, our data suggest that assortative mating between the two subspecies may operate at a behavioural or species recognition level rather than through fertilization, genetic incompatibility or developmental inhibition. Nevertheless, hybridization between the two subspecies of possum clearly occurs, creating the opportunity for novel genetic combinations that would not occur in their natural ranges and which is especially likely given that multiple contact zones occur in New Zealand. This discovery has implications for wildlife management in New Zealand because multiple contact zones are likely to influence the dispersal patterns of possums and because differential susceptibility to baiting with sodium fluoroacetate between possums of different origins may promote novel genetic forms.

The genetic signature left by the range expansion of red foxes in Australia is detectable after more than 80 years of population stability.

Reconstructing biological invasions from historical sources can provide insights into how they occur but are difficult to do when invasions are poorly documented. Genetic signatures left by invaders can also offer insights into invasion routes, points of origin and general biology but often present conclusions that are contradictory to expectations. Here, we test the ability of continental-wide microsatellite genotype data from 29 loci and 3122 samples to reconstruct the well-documented invasion of red foxes Vulpes vulpes from the United Kingdom into Australia over 150 years ago, an invasion that has led to the extinction of many native species. Our analysis reveals several key signals of invasion evident in Australian foxes. They display lower levels of diversity than foxes sampled from the UK, exhibit clines in diversity from the point of introduction (south-east Australia) to the edge of their range, and show strong evidence of allele surfing in westerly and north-easterly directions. These characteristics are consistent with a single point of origin followed by rapid expansion in westerly and north-easterly directions as suggested by historical records. We also find little genetic structure in foxes across Australia with only the vast Nullarbor Plains and Great Victoria Desert region presenting a detectable barrier to their dispersal. As such, no mainland region within the current range of foxes can be considered genetically isolated and therefore appropriate for localised eradication efforts. Overall, our analyses demonstrate the ability of comprehensive population genetic studies to reconstruct invasion histories even after more than 80 years since colonisation was stabilised.

slimr: An R package for tailor-made integrations of data in population genomic simulations over space and time.

Software for realistically simulating complex population genomic processes is revolutionizing our understanding of evolutionary processes, and providing novel opportunities for integrating empirical data with simulations. However, the integration between standalone simulation software and R is currently not well developed. Here, we present slimr, an R package designed to create a seamless link between standalone software SLiM >3.0, one of the most powerful population genomic simulation frameworks, and the R development environment, with its powerful data manipulation and analysis tools. We show how slimr facilitates smooth integration between genetic data, ecological data and simulation in a single environment. The package enables pipelines that begin with data reading, cleaning and manipulation, proceed to constructing empirically based parameters and initial conditions for simulations, then to running numerical simulations and finally to retrieving simulation results in a format suitable for comparisons with empirical data - aided by advanced analysis and visualization tools provided by R. We demonstrate the use of slimr with an example from our own work on the landscape population genomics of desert mammals, highlighting the advantage of having a single integrated tool for both data analysis and simulation. slimr makes the powerful simulation ability of SLiM directly accessible to R users, allowing integrated simulation projects that incorporate empirical data without the need to switch between software environments. This should provide more opportunities for evolutionary biologists and ecologists to use realistic simulations to better understand the interplay between ecological and evolutionary processes.

Swinging back from the brink? Polygamous mating strategies revealed for an iconic threatened freshwater fish.

Catastrophic fish death events are increasing in frequency and severity globally. A series of major recent fish deaths in the semi-arid lower Darling-Baaka river system (LDBR) of Australia are emblematic of these issues with tens of millions of native fish perishing. In 2018-2019 there was a major death event for Australia's largest freshwater fish, Murray cod (Maccullochella peelii). To aid the recovery and guide restoration activities of local Murray cod populations, it is essential to gather information on the mating strategies and effective population size following the fish death event. After the fish deaths, we collected larvae during the 2020 and 2021 breeding seasons and used single nucleotide polymorphisms (SNPs) to provide insight mating strategies and to estimate effective population size. Larvae were detected in both years along the entire length of the LDBR. Sixteen percent of the inferred breeding individuals were found to contribute to multiple pairings, confirming a complex and polygamous mating system. A high frequency of polygamy was evident both within and between years with 100 % polygamy identified among parents that produced offspring in both 2020 and 2021 and 95 % polygamy identified among parents involved in multiple spawning events within years. Post-larval Murray cod samples collected between 2016 and 2021 were co-analysed to further inform kinship patterns. Again, monogamy was rare with no confirmed cases of the same male-female pair contributing to multiple breeding events within or between seasons. Effective population size based on Murray cod collected after the fish death event was estimated at 721.6 (CI 471-1486), though this has likely declined following a subsequent catastrophic fish death event in the LDBR in March 2023. Our data provide insight into the variability of Murray cod mating strategies, and we anticipate that this knowledge will assist in planning conservation actions to ultimately help recover a species in crisis.

Climate warming drives a temperate-zone lizard to its upper thermal limits, restricting activity, and increasing energetic costs.

Lizards are considered vulnerable to climate change because many operate near their thermal maxima. Exposure to higher temperatures could reduce activity of these animals by forcing them to shelter in thermal refugia for prolonged periods to avoid exceeding lethal limits. While rising temperatures should reduce activity in tropical species, the situation is less clear for temperate-zone species where activity can be constrained by both low and high temperatures. Here, we measure the effects of natural variation in environmental temperatures on activity in a temperate grassland lizard and show that it is operating near its upper thermal limit in summer even when sheltering in thermal refuges. As air temperatures increased above 32 °C, lizard activity declined markedly as individuals sought refuge in cool microhabitats while still incurring substantial metabolic costs. We estimate that warming over the last two decades has required these lizards to increase their energy intake up to 40% to offset metabolic losses caused by rising temperatures. Our results show that recent increases in temperature are sufficient to exceed the thermal and metabolic limits of temperate-zone grassland lizards. Extended periods of high temperatures could place natural populations of ectotherms under significantly increased environmental stress and contribute to population declines and extinction.

Quality indicators in intensive care medicine for Germany - fourth edition 2022.

The measurement of quality indicators supports quality improvement initiatives. The German Interdisciplinary Society of Intensive Care Medicine (DIVI) has published quality indicators for intensive care medicine for the fourth time now. After a scheduled evaluation after three years, changes in several indicators were made. Other indicators were not changed or only minimally. The focus remained strongly on relevant treatment processes like management of analgesia and sedation, mechanical ventilation and weaning, and infections in the ICU. Another focus was communication inside the ICU. The number of 10 indicators remained the same. The development method was more structured and transparency was increased by adding new features like evidence levels or author contribution and potential conflicts of interest. These quality indicators should be used in the peer review in intensive care, a method endorsed by the DIVI. Other forms of measurement and evaluation are also reasonable, for example in quality management. This fourth edition of the quality indicators will be updated in the future to reflect the recently published recommendations on the structure of intensive care units by the DIVI.

Reproductive Strategies and Population Genetic Structure in Two Dryland River Floodplain Plants, Marsilea drummondii and Eleocharis acuta.

Aquatic plants share a range of convergent reproductive strategies, such as the ability to reproduce both sexually and asexually through vegetative growth. In dryland river systems, floodplain inundation is infrequent and irregular, and wetlands consist of discrete and unstable habitat patches. In these systems, life history strategies such as long-distance dispersal, seed longevity, self-fertilisation, and reproduction from vegetative propagules are important strategies that allow plants to persist. Using two aquatic plants, Marsilea drummondii and Eleocharis acuta, we investigated the proportions of sexual and asexual reproduction and self-fertilisation by employing next-generation sequencing approaches, and we used this information to understand the population genetic structure of a large inland floodplain in western New South Wales (NSW), Australia. Asexual vegetative reproduction and self-fertilisation were more common in M. drummondii, but both species used sexual reproduction as the main mode of reproduction. This resulted in a highly differentiated genetic structure between wetlands and a similar genetic structure within wetlands. The similarity in genetic structure was influenced by the wetland in the two species, highlighting the influence of the floodplain landscape and hydrology on structuring population genetic structure. The high levels of genetic variation among wetlands and the low variation within wetlands suggests that dispersal and pollination occur within close proximity and that gene flow is restricted. This suggests a reliance on locally sourced (persistent) seed, rather than asexual (clonal) reproduction or recolonisation via dispersal, for the population maintenance of plants in dryland rivers. This highlights the importance of floodplain inundation to promote seed germination, establishment, and reproduction in dryland regions.

Food web structure and biocontrol in a four-trophic level system across a landscape complexity gradient.

Decline in landscape complexity owing to agricultural intensification may affect biodiversity, food web complexity and associated ecological processes such as biological control, but such relationships are poorly understood. Here, we analysed food webs of cereal aphids, their primary parasitoids and hyperparasitoids in 18 agricultural landscapes differing in structural complexity (42-93% arable land). Despite little variation in the richness of each trophic group, we found considerable changes in trophic link properties across the landscape complexity gradient. Unexpectedly, aphid-parasitoid food webs exhibited a lower complexity (lower linkage density, interaction diversity and generality) in structurally complex landscapes, which was related to the dominance of one aphid species in complex landscapes. Nevertheless, primary parasitism, as well as hyperparasitism, was higher in complex landscapes, with primary parasitism reaching levels for potentially successful biological control. In conclusion, landscape complexity appeared to foster higher parasitism rates, but simpler food webs, thereby casting doubt on the general importance of food web complexity for ecosystem functioning.

Solving the puzzle of mercury fate and emissions by coal-fired power plants: The potential of hydrodynamic-atmospheric modelling.

There is currently a significant gap in knowledge about the emission and deposition of mercury (Hg) from coal-fired power plants in Australia. To fill this gap, we propose a novel method that combines several sources of information (stratigraphic data, hydrodynamic modelling and atmospheric modelling), to identify the sources and fates of Hg emitted from coal-fired power plants. The stratigraphic record from Lake Macquarie (Australia) shows that mercury deposition increased up to 7-times since the 1950s, which is when coal-fired power plants were commissioned in the catchment. The stratigraphy also shows a decrease in Hg deposition with power plant retrofits. Using results from multiple models (statistical modelling, hydrodynamic modelling, particle density modelling and atmospheric emissions modelling), we found that ash dams contribute little Hg to Lake Macquarie. Instead, most of the Hg contamination in the lake is a result of atmospheric emissions from the power plants, and these power plants are also depositing Hg in the urban areas to the west of the lake. Our results demonstrate that the multi-proxy approach demonstrated in the paper can be used to provide clues as to the source of Hg, so that appropriate mitigation strategies and regulatory frameworks can be implemented.

Evolution of climate niches in European mammals?

Our ability to predict consequences of climate change is severely impaired by the lack of knowledge on the ability of species to adapt to changing environmental conditions. We used distribution data for 140 mammal species in Europe, together with data on climate, land cover and topography, to derive a statistical description of their realized climate niche. We then compared climate niche overlap of pairs of species, selected on the basis of phylogenetic information. In contrast to expectations, related species were not similar in their climate niche. Rather, even species pairs that had a common ancestor less than 1 Ma already display very high climate niche distances. We interpret our finding as a strong interspecific competitive constraint on the realized niche, rather than a rapid evolution of the fundamental niche. If correct, our results imply a very limited usefulness of climate niche models for the prediction of future mammal distributions.

Experimental and Numerical Impact Analysis of Automotive Bumper Brackets Made of 2D Triaxially Braided CFRP Composites.

The impact behavior of carbon fiber epoxy bumper brackets reinforced with 2D biaxial and 2D triaxial braids was experimentally and numerically analyzed. For this purpose, a phenomenological damage model was modified and implemented as a user material in ABAQUS. It was hypothesized that all input parameters could be determined from a suitable high-speed test program. Therefore, novel impact test device was designed, developed and integrated into a drop tower. Drop tower tests with different impactor masses and impact velocities at different bumper bracket configurations were conducted to compare the numerically predicted deformation and damage behavior with experimental evidence. Good correlations between simulations and tests were found, both for the global structural deformation, including fracture, and local damage entities in the impact zone. It was proven that the developed phenomenological damage models can be fully applied for present-day industrial problems.

Advantages of volunteer-based biodiversity monitoring in Europe.

Without robust and unbiased systems for monitoring, changes in natural systems will remain enigmatic for policy makers, leaving them without a clear idea of the consequences of any environmental policies they might adopt. Generally, biodiversity-monitoring activities are not integrated or evaluated across any large geographic region. The EuMon project conducted the first large-scale evaluation of monitoring practices in Europe through an on-line questionnaire and is reporting on the results of this survey. In September 2007 the EuMon project had documented 395 monitoring schemes for species, which represents a total annual cost of about 4 million euro, involving more than 46,000 persons devoting over 148,000 person-days/year to biodiversity-monitoring activities. Here we focused on the analysis of variations of monitoring practices across a set of taxonomic groups (birds, amphibians and reptiles, mammals, butterflies, plants, and other insects) and across 5 European countries (France, Germany, Hungary, Lithuania, and Poland). Our results suggest that the overall sampling effort of a scheme is linked with the proportion of volunteers involved in that scheme. Because precision is a function of the number of monitored sites and the number of sites is maximized by volunteer involvement, our results do not support the common belief that volunteer-based schemes are too noisy to be informative. Just the opposite, we believe volunteer-based schemes provide relatively reliable data, with state-of-the-art survey designs or data-analysis methods, and consequently can yield unbiased results. Quality of data collected by volunteers is more likely determined by survey design, analytical methodology, and communication skills within the schemes rather than by volunteer involvement per se.