Major Histocompatibility Complex (MHC) genes encode for proteins that recognize foreign protein antigens to initiate T-cell mediated adaptive immune responses. They are often the most polymorphic genes in vertebrate genomes. How evolution maintains this diversity is still an unsettled issue. Three main hypotheses seek to explain the maintenance of MHC diversity by invoking pathogen-mediated selection: heterozygote advantage, frequency-dependent selection, and fluctuating selection across landscapes...
Wed Aug 19, 2020 03:00
Although molecular mechanisms associated with the generation of mutations are highly conserved across taxa, there is widespread variation in mutation rates between evolutionary lineages. When phylogenies are reconstructed based on nucleotide sequences, such variation is typically accounted for by the assumption of a relaxed molecular clock, which, however, is just a statistical distribution of mutation rates without any underlying biological mechanism. Here, we propose that variation in accumulated...
Wed Aug 19, 2020 03:00
Dominant theory maintains that organisms age due to resource allocation trade-offs between the immortal germline and the disposable soma. Strikingly, adulthood-only downregulation of insulin signalling, an evolutionarily conserved pathway regulating resource allocation between reproduction and soma, increases lifespan and offspring fitness without fecundity cost in the nematode, Caenorhabditis elegans. Nevertheless, theory suggests that reduced germline maintenance can be a hidden cost of lifespan...
Wed Aug 19, 2020 03:00
Inference using mathematical models of infectious disease dynamics is a powerful tool to analyse epidemiological data and elucidate pathogen life cycles. Key epidemiological parameters can be estimated from demographic time series by computing the likelihood of alternative models of pathogen transmission. Here we use this inference approach to analyze data from an evolution experiment in which we monitored both the epidemiology and the evolution of the temperate bacteriophage during an epidemic....
Wed Aug 19, 2020 03:00
Evolutionary genetic studies have uncovered abundant evidence for genomic hotspots of phenotypic evolution, as well as biased patterns of mutations at those loci. However, the theoretical basis for this concentration of particular types of mutations at particular loci remains largely unexplored. In addition, historical contingency is known to play a major role in evolutionary trajectories, but has not been reconciled with the existence of such hotspots. For example, do the appearance of hotspots...
Wed Aug 19, 2020 03:00
Metabarcoding of Metazoa using mitochondrial genes may be confounded by both the accumulation of PCR and sequencing artefacts and the co-amplification of nuclear mitochondrial pseudogenes (NUMTs). The application of read abundance thresholds and denoising methods is efficient in reducing noise accompanying authentic mitochondrial amplicon sequence variants (ASVs). However, these procedures do not fully account for the complex nature of concomitant sequences and the highly variable DNA contribution...
Wed Aug 19, 2020 03:00
Gene duplication is an important source of evolutionary innovation, but the adaptive division-of-labor between duplicates can be opposed by ongoing gene conversion between them. Here we document a tandem duplication of Na+,K+-ATPase subunit 1 (ATP1A1) shared by frogs in the genus Leptodactylus, a group of species that feeds on toxic toads. One ATP1A1 paralog evolved resistance to toad toxins while the other paralog retained ancestral susceptibility. We show that the two Leptodactylus paralogs are...
Wed Aug 19, 2020 03:00
Ancient DNA sampling methods--although optimized for efficient DNA extraction--are destructive, relying on drilling or cutting and powdering (parts of) bones and teeth. As the field of ancient DNA has grown, so have concerns about the impact of destructive sampling of the skeletal remains from which ancient DNA is obtained. Due to a particularly high concentration of endogenous DNA, the cementum of tooth roots is often targeted for ancient DNA sampling, but standard destructive sampling methods often...
Wed Aug 19, 2020 03:00
Organisms rely on plasticity to track environmental variation within their native range. However, it remains unclear how adaptation and plasticity interact, and how adaptive divergence affects the evolution of plasticity. To test for variation in plastic responses among two closely related but ecologically divergent ragwort species (Senecio, Asteraceae), we sampled c.40 genotypes of each species from natural populations. We then transplanted multiple clones of each genotype into four field sites...
Tue Aug 18, 2020 03:00
Hepatitis deltavirus (HDV) is an obligate hyper-parasite that increases the severity of hepatitis B virus (HBV) in humans. The origins of HDV and the mechanisms through which it and related animal deltaviruses diversify are unknown. We report the epidemiology and evolutionary history of new mammal-infecting deltaviruses. Despite geographic under-representation in over 348 terabases of globally-distributed RNA sequence data from mammals, deltaviruses originated exclusively from the Americas, infecting...
Tue Aug 18, 2020 03:00
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