Search results for "Biological Evolution"
showing 10 items of 522 documents
Evolutionary distances corrected for purifying selection and ancestral polymorphisms.
2019
Abstract Evolutionary distance formulas that take into account effects due to ancestral polymorphisms and purifying selection are obtained on the basis of the full solution of Jukes–Cantor and Kimura DNA substitution models. In the case of purifying selection two different methods are developed. It is shown that avoiding the dimensional reduction implicitly carried out in the conventional model solving is instrumental to incorporate the quoted effects into the formalism. The problem of estimating the numerical values of the model parameters, as well as those of the correction terms, is not addressed.
Tremblaya phenacola PPER: an evolutionary beta-gammaproteobacterium collage
2017
Many insects rely on bacterial endosymbionts to obtain nutrients that are scarce in their highly specialized diets. The most surprising example corresponds to the endosymbiotic system found in mealybugs from subfamily Pseudococcinae in which two bacteria, the betaproteobacterium 'Candidatus Tremblaya princeps' and a gammaproteobacterium, maintain a nested endosymbiotic consortium. In the sister subfamily Phenacoccinae, however, a single beta-endosymbiont, 'Candidatus Tremblaya phenacola', has been described. In a previous study, we detected a trpB gene of gammaproteobacterial origin in 'Ca. Tremblaya phenacola' from two Phenacoccus species, apparently indicating an unusual case of horizonta…
Under pressure: phenotypic divergence and convergence associated with microhabitat adaptations in Triatominae
2021
AbstractBackgroundTriatomine bugs, the vectors of Chagas disease, associate with vertebrate hosts in highly diverse ecotopes. When these blood-sucking bugs adapt to new microhabitats, their phenotypes may change. Although understanding phenotypic variation is key to the study of adaptive evolution and central to phenotype-based taxonomy, the drivers of phenotypic change and diversity in triatomines remain poorly understood.Methods/FindingsWe combined a detailed phenotypic appraisal (including morphology and morphometrics) with mitochondrialcytband nuclear ITS2 DNA-sequence analyses to studyRhodnius ecuadoriensispopulations from across the species’ range. We found three major, naked-eye phen…
Evolutionary History of the Nesophontidae, the Last Unplaced Recent Mammal Family
2016
The mammalian evolutionary tree has lost several major clades through recent human-caused extinctions. This process of historical biodiversity loss has particularly affected tropical island regions such as the Caribbean, an area of great evolutionary diversification but poor molecular preservation. The most enigmatic of the recently extinct endemic Caribbean mammals are the Nesophontidae, a family of morphologically plesiomorphic lipotyphlan insectivores with no consensus on their evolutionary affinities, and which constitute the only major recent mammal clade to lack any molecular information on their phylogenetic placement. Here, we use a palaeogenomic approach to place Nesophontidae with…
Computational Fluid Dynamics Suggests Ecological Diversification among Stem-Gnathostomes.
2020
Summary The evolutionary assembly of the vertebrate bodyplan has been characterized as a long-term ecological trend toward increasingly active and predatory lifestyles, culminating in jawed vertebrates that dominate modern vertebrate biodiversity [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ]. This contrast is no more stark than between the earliest jawed vertebrates and their immediate relatives, the extinct jawless, dermal armor-encased osteostracans, which have conventionally been interpreted as benthic mud-grubbers with poor swimming capabilities and low maneuverability [ 9 , 10 , 11 , 12 ]. Using computational fluid dynamics, we show that osteostracan headshield morphology is compatible with a dive…
Mitigating anticipated effects of systematic errors supports sister-group relationship between Xenacoelomorpha and Ambulacraria.
2019
International audience; Xenoturbella and the acoelomorph worms (Xenacoelomorpha) are simple marine animals with controversial affinities. They have been placed as the sister group of all other bilaterian animals (Nephrozoa hypothesis), implying their simplicity is an ancient characteristic ]; alternatively, they have been linked to the complex Ambulacraria (echinoderms and hemichordates) in a clade called the Xenambulacraria , suggesting their simplicity evolved by reduction from a complex ancestor. The difficulty resolving this problem implies the phylogenetic signal supporting the correct solution is weak and affected by inadequate modeling, creating a misleading non-phylogenetic signal. …
A functional zeaxanthin epoxidase from red algae shedding light on the evolution of light-harvesting carotenoids and the xanthophyll cycle in photosy…
2017
The epoxy-xanthophylls antheraxanthin and violaxanthin are key precursors of light-harvesting carotenoids and participate in the photoprotective xanthophyll cycle. Thus, the invention of zeaxanthin epoxidase (ZEP) catalyzing their formation from zeaxanthin has been a fundamental step in the evolution of photosynthetic eukaryotes. ZEP genes have only been found in Viridiplantae and chromalveolate algae with secondary plastids of red algal ancestry, suggesting that ZEP evolved in the Viridiplantae and spread to chromalveolates by lateral gene transfer. By searching publicly available sequence data from eleven red algae covering all currently recognized red algal classes we identified ZEP cand…
Using host species traits to understand the Wolbachia infection distribution across terrestrial beetles.
2019
AbstractKnowledge of Wolbachia prevalence with respect to its hosts is restricted mainly to taxonomic/phylogenetic context. In contrast, relations between infection and most host’s ecological and biological traits are poorly understood. This study aimed to elaborate on relations between bacteria and its beetle hosts in taxonomic and the ecological contexts. In particular, the goal is to verify which ecological and biological traits of beetles could cause them to be prone to be infected. Verification of Wolbachia infection status across 297 beetle taxa showed that approximately 27% of taxa are infected by supergroups A and B. Only minor support for coevolution between bacteria and its beetle…
Co-regulation of paralog genes in the three-dimensional chromatin architecture.
2016
Paralog genes arise from gene duplication events during evolution, which often lead to similar proteins that cooperate in common pathways and in protein complexes. Consequently, paralogs show correlation in gene expression whereby the mechanisms of co-regulation remain unclear. In eukaryotes, genes are regulated in part by distal enhancer elements through looping interactions with gene promoters. These looping interactions can be measured by genome-wide chromatin conformation capture (Hi-C) experiments, which revealed self-interacting regions called topologically associating domains (TADs). We hypothesize that paralogs share common regulatory mechanisms to enable coordinated expression acco…
Sublethal streptomycin concentrations and lytic bacteriophage together promote resistance evolution.
2017
Sub-minimum inhibiting concentrations (sub-MICs) of antibiotics frequently occur in natural environments owing to wide-spread antibiotic leakage by human action. Even though the concentrations are very low, these sub-MICs have recently been shown to alter bacterial populations by selecting for antibiotic resistance and increasing the rate of adaptive evolution. However, studies are lacking on how these effects reverberate into key ecological interactions, such as bacteria-phage interactions. Previously, co-selection of bacteria by phages and antibiotic concentrations exceeding MICs has been hypothesized to decrease the rate of resistance evolution because of fitness costs associated with re…