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Ecological networks are more sensitive to plant than to animal extinction under climate change
(2016)
Impacts of climate change on individual species are increasingly well documented, but we lack understanding of how these effects propagate through ecological communities. Here we combine species distribution models with ecological network analyses to test potential impacts of climate change on >700 plant and animal species in pollination and seed-dispersal networks from central Europe. We discover that animal species that interact with a low diversity of plant species have narrow climatic niches and are most vulnerable to climate change. In contrast, biotic specialization of plants is not related to climatic niche breadth and vulnerability. A simulation model incorporating different scenarios of species coextinction and capacities for partner switches shows that projected plant extinctions under climate change are more likely to trigger animal coextinctions than vice versa. This result demonstrates that impacts of climate change on biodiversity can be amplified via extinction cascades from plants to animals in ecological networks.
In recent years, interest in the environmental occurrence and effects of microplastics (MPs) has shifted towards our inland waters, and in this chapter we provide an overview of the issues that may be of concern for freshwater environments. The term ‘contaminant of emerging concern’ does not only apply to chemical pollutants but to MPs as well because it has been detected ubiquitously in freshwater systems. The environmental release of MPs will occur from a wide variety of sources, including emissions from wastewater treatment plants and from the degradation of larger plastic debris items. Due to the chemical makeup of plastic materials, receiving environments are potentially exposed to a mixture of micro- and nano-sized particles, leached additives, and subsequent degradation products, which will become bioavailable for a range of biota. The ingestion of MPs by aquatic organisms has been demonstrated, but the long-term effects of continuous exposures are less well understood. Technological developments and changes in demographics will influence the types of MPs and environmental concentrations in the future, and it will be important to develop approaches to mitigate the input of synthetic polymers to freshwater ecosystems.
The ubiquitous detection of microplastics in aquatic ecosystems promotes the concern for adverse impacts on freshwater ecosystems. The wide variety of material types, sizes, shapes, and physicochemical properties renders interactions with biota via multiple pathways probable.
So far, our knowledge about the uptake and biological effects of microplastics comes from laboratory studies, applying simplified exposure regimes (e.g., one polymer and size, spherical shape, high concentrations) often with limited environmental relevance. However, the available data illustrates species- and material-related interactions and highlights that microplastics represent a multifaceted stressor. Particle-related toxicities will be driven by polymer type, size, and shape. Chemical toxicity is driven by the adsorption-desorption kinetics of additives and pollutants. In addition, microbial colonization, the formation of hetero-aggregates, and the evolutionary adaptations of the biological receptor further increase the complexity of microplastics as stressors. Therefore, the aim of this chapter is to synthesize and critically revisit these aspects based on the state of the science in freshwater research. Where unavailable we supplement this with data on marine biota. This provides an insight into the direction of future research.
In this regard, the challenge is to understand the complex interactions of biota and plastic materials and to identify the toxicologically most relevant characteristics of the plethora of microplastics. Importantly, as the direct biological impacts of natural particles may be similar, future research needs to benchmark synthetic against natural materials. Finally, given the scale of the research question, we need a multidisciplinary approach to understand the role of microplastics in a multiple-particle world.
Mutations are the ultimate basis of evolution, yet their occurrence rate is known only for few species. We directly estimated the spontaneous mutation rate and the mutational spectrum in the nonbiting midge C. riparius with a new approach. Individuals from ten mutation accumulation lines over five generations were deep genome sequenced to count de novo mutations that were not present in a pool of F1 individuals, representing parental genotypes. We identified 51 new single site mutations of which 25 were insertions or deletions and 26 single nucleotide mutations. This shift in the mutational spectrum compared to other organisms was explained by the high A/T content of the species. We estimated a haploid mutation rate of 2.1 × 10−9 (95% confidence interval: 1.4 × 10−9 – 3.1 × 10-9) that is in the range of recent estimates for other insects and supports the drift barrier hypothesis. We show that accurate mutation rate estimation from a high number of observed mutations is feasible with moderate effort even for nonmodel species.
The Asian tiger mosquito, Aedes albopictus (Diptera: Culicidae, SKUSE), is an important threat to public health due to its rapid spread and its potential as a vector. The eggs of Ae. albopictus are the most cold resistant life stage and thus, the cold hardiness of eggs is used to predict the future occurrence of the species in distribution models. However, the mechanism of cold hardiness has yet to be revealed. To address this question, we analyzed the layers of diapausing and cold acclimatized eggs of a temperate population of Ae. albopictus in a full factorial test design using transmission electron microscopy. We reviewed the hypotheses that a thickened wax layer or chorion is the cause of cold hardiness but found no evidence. As a result of the induced diapause, the thickness of the dark endochorion as a layer of high electron density and thus an assumed location for waxes was decreasing. We therefore hypothesized a qualitative alteration of the wax layer due to compaction. Cold acclimation was causing an increase in the thickness of the middle serosa cuticle indicating a detachment of serosa membrane from the endochorion as a potential adaptation strategy to isolate inoculating ice formations in the inter-membranous space.
Biotic interchange after the connection of previously independently evolving floras and faunas is thought to be one of the key factors that shaped global biodiversity as we see it today. However, it was not known how biotic interchange develops over longer time periods of several million years following the secondary contact of different biotas. Here we present a novel method to investigate the temporal dynamics of biotic interchange based on a phylogeographical meta-analysis by calculating the maximal number of observed dispersal events per million years given the temporal uncertainty of the underlying time-calibrated phylogenies. We show that biotic influx from mainland Asia onto the Indian subcontinent after Eocene continental collision was not a uniform process, but was subject to periods of acceleration, stagnancy and decrease. We discuss potential palaeoenvironmental causes for this fluctuation.
Phylogenetic reconstruction from transposable elements (TEs) offers an additional perspective to study evolutionary processes. However, detecting phylogenetically informative TE insertions requires tedious experimental work, limiting the power of phylogenetic inference. Here, we analyzed the genomes of seven bear species using high-throughput sequencing data to detect thousands of TE insertions. The newly developed pipeline for TE detection called TeddyPi (TE detection and discovery for Phylogenetic Inference) identified 150,513 high-quality TE insertions in the genomes of ursine and tremarctine bears. By integrating different TE insertion callers and using a stringent filtering approach, the TeddyPi pipeline produced highly reliable TE insertion calls, which were confirmed by extensive in vitro validation experiments. Analysis of single nucleotide substitutions in the flanking regions of the TEs shows that these substitutions correlate with the phylogenetic signal from the TE insertions. Our phylogenomic analyses show that TEs are a major driver of genomic variation in bears and enabled phylogenetic reconstruction of a well-resolved species tree, despite strong signals for incomplete lineage sorting and introgression. The analyses show that the Asiatic black, sun, and sloth bear form a monophyletic clade, in which phylogenetic incongruence originates from incomplete lineage sorting. TeddyPi is open source and can be adapted to various TE and structural variation callers. The pipeline makes it possible to confidently extract thousands of TE insertions even from low-coverage genomes (∼10×) of nonmodel organisms. This opens new possibilities for biologists to study phylogenies and evolutionary processes as well as rates and patterns of (retro-)transposition and structural variation.
The lichen-forming genus Pertusaria under its current circumscription is polyphyletic and its phylogenetic affiliations are uncertain. Here we study the species of the genera Pertusaria and Varicellaria which containlecanoric acid as major constituent, have disciform apothecia, strongly amyloid asci, non-amyloid hymenial gel, 1-2-spored asci, and 1- or 2-celled ascospores with thick, 1-layered walls. We infer phylogenetic relationships using maximum likelihood and Bayesian analyses based on four molecular loci (mtSSU, nuLSU rDNA, and the protein-coding, nuclear RPB1 and MCM7 genes). Our results show that the lecanoric acid-containing species form a well-supported, monophyletic group, which is only distantly related to Pertusaria s.str. The phylogenetic position of this clade is unclear, but placement in Pertusaria s.str. is rejected using alternative hypothesis testing. The circumscription of the genus Varicellaria is enlarged to also include species with non-septate ascospores. Seven species are accepted in the genus: Varicellaria culbersonii (Vězda) Schmitt & Lumbsch, comb. nov., Varicellaria hemisphaerica (Flörke) Schmitt & Lumbsch, comb. nov., Varicellaria kasandjeffii (Szatala) Schmitt & Lumbsch, comb. nov., Varicellaria lactea (L.) Schmitt & Lumbsch, comb. nov., Varicellaria philippina (Vain.) Schmitt & Lumbsch, comb. nov., Varicellaria rhodocarpa (Körb.) Th. Fr., and Varicellaria velata (Turner) Schmitt & Lumbsch, comb. nov. A key to the species of Varicellaria is provided.
Erstmals trägt dieses nationale Assessment den Forschungsstand zum Klimawandel umfassend für alle Themenbereiche und gesellschaftlichen Sektoren zusammen. Womit müssen wir in Deutschland rechnen, welche Auswirkungen werden die Klimaveränderungen auf Wirtschaft und Gesellschaft haben, und wie können wir uns wappnen? 126 Autoren aus ganz Deutschland äußern sich zu Themen wie bereits beobachtete und zukünftige Veränderungen, Wetterkatastrophen und deren Folgen, den Projektionen für die Zukunft, den Risiken sowie möglichen Anpassungsstrategien.
Die Autoren stellen in verständlicher Sprache den aktuellen Forschungsstand dar und veranschaulichen die wichtigsten Gedanken in Grafiken und Tabellen. Alle Texte wurden mehrfach wissenschaftlich begutachtet. Klimawandel in Deutschland ist die erste Gesamtschau zu dem Themenkomplex, benennt offene Fragestellungen und liefert eine Grundlage für Entscheidungen im Zusammenhang mit dem Klimawandel.
Deutschland reiht sich damit ein in die Liste von Ländern wie die Vereinigten Staaten, Österreich und Großbritannien, in denen derartige Berichte bereits vorliegen.