Tasmanian devils (Sarcophilus harrisii) are evolving in response to a unique transmissible cancer, devil facial tumour disease (DFTD), first described in 1996. Persistence of wild populations and the recent emergence of a second independently evolved transmissible cancer suggest that transmissible cancers may be a recurrent feature in devils. We used a targeted sequencing approach, RAD-capture, to identify genomic regions subject to rapid evolution in approximately 2,500 devils as DFTD spread across...
Fri Aug 07, 2020 03:00
Autochthonous Sudanese cattle breeds, namely Baggara for beef and Butana and Kenana for dairy, are characterized by their adaptive characteristics and high performance in hot and dry agro-ecosystems, are used largely by nomadic and semi-nomadic pastoralists. Here we analyzed the diversity and genetic structure of the BoLA-DRB3 gene, a genetic locus linked to the immune response, for the indigenous cattle of Sudan and in the context of the global cattle repository. Blood samples (n=225) were taken...
Fri Aug 07, 2020 03:00
Horizontal gene transfer (HGT) allows organisms to share genetic material with non-offspring, and is typically considered beneficial for evolving populations. Recent unexplained observations suggest that HGT rates in nature are linked with environmental dynamics, being high in static environments but surprisingly low in fluctuating environments. Here, using a geometric model of adaptation, we show that this trend might arise from evolutionary constraints. During adaptation in our model, a population...
Fri Aug 07, 2020 03:00
Species are often defined by their ability to interbreed (i.e., Biological Species Concept), but determining how and why reproductive isolation arises between new species can be challenging. In the Mimulus tilingii species complex, three species (M. caespitosa, M. minor, and M. tilingii) are largely allopatric and grow exclusively at high elevations (>2000m). The extent to which geographic separation has shaped patterns of divergence among the species is not well understood. In this study, we...
Fri Aug 07, 2020 03:00
Where is evolution fastest? The biotic interactions hypothesis proposes that greater species richness creates more ecological opportunity, driving faster evolution at low latitudes, whereas the "empty niches" hypothesis proposes that ecological opportunity is greater where diversity is low, spurring faster evolution at high latitudes. Here we test these contrasting predictions by analyzing rates of bird beak evolution for a global dataset of 1141 sister pairs of birds. We find that beak size evolves...
Fri Aug 07, 2020 03:00
Mating systems have profound effects on genetic diversity and compatibility. The convergent evolution of self-fertilization in three Caenorhabditis species provides a powerful lens to examine causes and consequences of mating system transitions. Among the selfers, C. tropicalis is the least genetically diverse and most afflicted by outbreeding depression. We generated a chromosomal-scale genome for C. tropicalis and surveyed global diversity. Population structure is very strong, and islands of extreme...
Fri Aug 07, 2020 03:00
Sex chromosomes are generally derived from a pair of autosomes that have acquired a locus controlling sex. Sex chromosomes usually evolve reduced recombination around this locus and undergo a long process of molecular divergence. Although sex chromosomes have been intensively studied in several model taxa, the actual loci controlling sex are difficult to identify in highly diverged sex chromosomes, hence they are known in relatively few species. Taxa with evolutionarily young sex chromosomes can...
Fri Aug 07, 2020 03:00
Theory predicts that the sexes can achieve greater fitness if loci with sexually antagonistic polymorphisms become linked to the sex determining loci, and this can favour the spread of reduced recombination around sex determining regions. Given that sex-linked regions are frequently repetitive and highly heterozygous, few complete Y chromosome assemblies are available to test these ideas. The guppy system (Poecilia reticulata) has long been invoked as an example of sex chromosome formation resulting...
Fri Aug 07, 2020 03:00
Identifying age-dependent trade-offs between reproductive effort and survival in wild organisms is central for understanding the evolutionary mechanisms of senescence. According to the disposable soma theory, early-life energy investments in reproduction compromise late-life investments in somatic maintenance - leading to senescence. Once thought to only be detectable in captive populations, senescence has recently been documented by several longitudinal studies of wild organisms. However, some reproductive...
Fri Aug 07, 2020 03:00
Background: New active ingredients, mostly repurposed from the agricultural sector, are gradually being introduced into malaria vector control programs. Prior to scaling up novel insecticides, it is vital to assess if their use in agriculture has already selected mosquito populations with reduced susceptibility in some areas. The aim of the present study was to determine if the use of neonicotinoids in agricultural pest management could drive resistance to clothianidin - a neonicotinoid recently...
Fri Aug 07, 2020 03:00
The causes of rate variation among sites within proteins are as yet poorly understood. Here, we compare the spatial autocorrelation of non-synonymous substitutions among species within diverse phylogenetic groups: Saccharomyces, Drosophila, Arabidopsis, and primates. Across these taxa, we find that amino acid substitutions exhibit excess clustering that extends over a 20-30 codon length (10-20 Angstrom distance) scale. We show that these substitutions cluster more strongly and exhibit compensatory...
Fri Aug 07, 2020 03:00
Oral venom systems evolved multiple times in numerous vertebrates enabling exploitation of unique predatory niches. Yet how and when they evolved remains poorly understood. Up to now, most research on venom evolution has focussed strictly on the toxins. However, using toxins present in modern day animals to trace the origin of the venom system is difficult, since they tend to evolve rapidly, show complex patterns of expression,an were incorporated into the venom arsenal relatively recently. Here...
Fri Aug 07, 2020 03:00
Interspecific gene flow by hybridization may weaken species barriers and adaptive divergence, but can also initiate reinforcement of reproductive isolation trough natural and sexual selection. The extent of interspecific gene flow and its consequences for the initiation and maintenance of species barriers in natural systems remain poorly understood, however. To assess genome-wide patterns of gene flow between the two closely related European dung fly species Sepsis cynipsea and Sepsis neocynipsea...
Fri Aug 07, 2020 03:00
It is generally accepted that the absence of recombination reduces the efficacy of natural selection for, or against, mutations. A special case is Muller's Ratchet (MR) whereby non-recombining genomes experience irreversible fitness decline due to the accumulation of deleterious mutations. MR has been a main hypothesis for sexual reproduction as well as many other biological phenomena. We now ask whether the fitness decline can indeed be stopped if an asexual population turns sexual to become recombining....
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