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1.
J Biosci ; 44(4)2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31502584

RESUMO

The role of genetic relatedness in social evolution has recently come under critical attention. These arguments are here critically analyzed, both theoretically and empirically. It is argued that when the conceptual structure of the theory of natural selection is carefully taken into account, genetic relatedness can be seen to play an indispensable role in the evolution of both facultative and advanced eusociality. Although reviewing the empirical evidence concerning the evolution of eusociality reveals that relatedness does not play a role in the initial appearance of helper phenotypes, this follows simply from the fact that natural selection - of which relatedness is a necessary component - does not play a causal role in the origin of any traits. Further, separating two logically distinct elements of causal explanation - necessity and sufficiency - explains why the debate lingers on: although relatedness plays a necessary role in the evolution of helping and advanced eusociality, relatedness alone is not sufficient for their appearance. Therefore, if the relatedness variable in a given data set is held at a uniformly high value, then it indeed may turn out that other factors occupy a more prominent role. However, this does not change the fact that high relatedness functions as a necessary background condition for the evolution of advanced eusociality.


Assuntos
Comportamento Animal/fisiologia , Aptidão Genética/fisiologia , Insetos/fisiologia , Seleção Genética/genética , Animais , Aptidão Genética/genética , Insetos/genética , Reprodução/genética , Reprodução/fisiologia , Seleção Genética/fisiologia , Comportamento Social , Sociobiologia
2.
Integr Comp Biol ; 59(3): 503-516, 2019 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-31270548

RESUMO

Temporal variation is a powerful source of selection on life history strategies and functional traits in natural populations. Theory predicts that the rate and predictability of fluctuations should favor distinct strategies, ranging from phenotypic plasticity to bet-hedging, which are likely to have important consequences for species distribution patterns and their responses to environmental change. To date, we have few empirical studies that test those predictions in natural systems, and little is known about how genetic, environmental, and developmental factors interact to define the "fluctuation niche" of species in temporally variable environments. In this study, we evaluated the effects of hydrological variability on fitness and functional trait variation in three closely related plant species in the genus Lasthenia that occupy different microhabitats within vernal pool landscapes. Using a controlled greenhouse experiment, we manipulated the mean and variability in hydrological conditions by growing plants at different depths with respect to a shared water table and manipulating the magnitude of stochastic fluctuations in the water table over time. We found that all species had similarly high relative fitness above the water table, but differed in their sensitivities to water table fluctuations. Specifically, the two species from vernal pools basins, where soil moisture is controlled by a perched water table, were negatively affected by the stochasticity treatments. In contrast, a species from the upland habitat surrounding vernal pools, where stochastic precipitation events control soil moisture variation, was insensitive to experimental fluctuations in the water table. We found strong signatures of genetic, environmental (plastic), and developmental variation in four traits that can influence plant hydrological responses. Three of these traits varied across plant development and among experimental treatments in directions that aligned with constitutive differences among species, suggesting that multiple sources of variation align to facilitate phenotypic matching with the hydrological environment in Lasthenia. We found little evidence for predicted patterns of phenotypic plasticity and bet-hedging in species and traits from predictable and stochastic environments, respectively. We propose that selection for developmental shifts in the hydrological traits of Lasthenia species has reduced or modified selection for plasticity at any given stage of development. Collectively, these results suggest that variation in species' sensitivities to hydrological stochasticity may explain why vernal pool Lasthenia species do not occur in upland habitat, and that all three species integrate genetic, environmental, and developmental information to manage the unique patterns of temporal hydrological variation in their respective microhabitats.


Assuntos
Asteraceae/fisiologia , Aptidão Genética/fisiologia , Traços de História de Vida , Dispersão Vegetal , Ciclo Hidrológico , Asteraceae/genética , Ecossistema , Estações do Ano
3.
Integr Comp Biol ; 59(2): 243-250, 2019 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-31268138

RESUMO

Ten years ago, two reviews clarified the need to tie glucocorticoid (GC) levels directly to survival and reproductive measures. Three primary hypotheses emerged from that work: the CORT-Fitness hypothesis, the CORT-Adaptation hypothesis, and the CORT-Tradeoff hypothesis. The two reviews have since been cited nearly 900 times, but no clear consensus has emerged supporting one hypothesis over another. We propose that resource availability may be a major confound across studies. Life-history investment is determined by both allocation and acquisition, but current literature testing among the three GC-fitness hypotheses rarely incorporate metrics of resource availability. In 1986, van Noordwijk and de Jong (vN and dJ) proposed the acquisition/allocation Y-model to explain positive versus negative correlations between reproduction and survival across individuals. Their model elevated resources as critical to evaluating individual allocation strategies (favoring reproduction vs. survival), and therefore provides the ideal framework for testing across the three CORT hypotheses. Here, we review the three hypotheses in light of the last 10 years of data, introduce the vN and dJ framework as a model for fitness/GC hypothesis testing, and discuss best practices for using this framework. We believe incorporation of resource availability will reduce unexplained variability in GC-fitness tests, clarify support among the three hypotheses, and allow for greater power in testing across other context dependencies (e.g., life-history strategy) that likely regulate differential allocation to reproduction versus survival as GCs increase.


Assuntos
Adaptação Fisiológica/fisiologia , Aptidão Genética/fisiologia , Glucocorticoides/fisiologia , Hidrocortisona/fisiologia , Traços de História de Vida , Reprodução/fisiologia
4.
Infect Immun ; 87(10)2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31331959

RESUMO

The soil-dwelling, saprophytic actinomycete Rhodococcus equi is a facultative intracellular pathogen of macrophages and causes severe bronchopneumonia when inhaled by susceptible foals. Standard treatment for R. equi disease is dual-antimicrobial therapy with a macrolide and rifampin. Thoracic ultrasonography and early treatment with antimicrobials prior to the development of clinical signs are used as means of controlling endemic R. equi infection on many farms. Concurrently with the increased use of macrolides and rifampin for chemoprophylaxis and the treatment of subclinically affected foals, a significant increase in the incidence of macrolide- and rifampin-resistant R. equi isolates has been documented. Previously, our laboratory demonstrated decreased fitness of R. equi strains that were resistant to macrolides, rifampin, or both, resulting in impaired in vitro growth in iron-restricted media and in soil. The objective of this study was to examine the effect of macrolide and/or rifampin resistance on intracellular replication of R. equi in equine pulmonary macrophages and in an in vivo mouse infection model in the presence and absence of antibiotics. In equine macrophages, the macrolide-resistant strain did not increase in bacterial numbers over time and the dual macrolide- and rifampin-resistant strain exhibited decreased proliferation compared to the susceptible isolate. In the mouse model, in the absence of antibiotics, the susceptible R. equi isolate outcompeted the macrolide- or rifampin-resistant strains.


Assuntos
Infecções por Actinomycetales/tratamento farmacológico , Antibacterianos/farmacologia , Claritromicina/farmacologia , Macrófagos Alveolares/microbiologia , Rhodococcus equi/efeitos dos fármacos , Rifampina/farmacologia , Infecções por Actinomycetales/imunologia , Infecções por Actinomycetales/microbiologia , Animais , Contagem de Colônia Microbiana , Farmacorresistência Bacteriana , Aptidão Genética/efeitos dos fármacos , Aptidão Genética/fisiologia , Cavalos , Fígado/efeitos dos fármacos , Fígado/microbiologia , Pulmão/efeitos dos fármacos , Pulmão/microbiologia , Macrófagos Alveolares/efeitos dos fármacos , Masculino , Camundongos , Camundongos Nus , Testes de Sensibilidade Microbiana , Cultura Primária de Células , Rhodococcus equi/fisiologia , Baço/efeitos dos fármacos , Baço/microbiologia
5.
Genetica ; 147(3-4): 291-302, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31240599

RESUMO

Meiotic recombination is evolutionarily ambiguous, as being associated with both benefits and costs to its bearers, with the resultant dependent on a variety of conditions. While existing theoretical models explain the emergence and maintenance of recombination, some of its essential features remain underexplored. Here we focus on one such feature, recombination plasticity, and test whether recombination response to stress is fitness-dependent. We compare desiccation stress effects on recombination rate and crossover interference in chromosome 3 between desiccation-sensitive and desiccation-tolerant Drosophila lines. We show that relative to desiccation-tolerant genotypes, desiccation-sensitive genotypes exhibit a significant segment-specific increase in single- and double-crossover frequencies across the pericentromeric region of chromosome 3. Significant changes (relaxation) in crossover interference were found for the interval pairs flanking the centromere and extending to the left arm of the chromosome. These results indicate that desiccation is a recombinogenic factor and that desiccation-induced changes in both recombination rate and crossover interference are fitness-dependent, with a tendency of less fitted individuals to produce more variable progeny. Such dependence may play an important role in the regulation of genetic variation in populations experiencing environmental challenges.


Assuntos
Troca Genética , Drosophila melanogaster/genética , Adaptação Fisiológica/genética , Animais , Centrômero/genética , Dessecação , Ontologia Genética , Aptidão Genética/fisiologia , Variação Genética/fisiologia
6.
Plant Biol (Stuttg) ; 21(5): 967-974, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31050864

RESUMO

The trait-fitness relationship influences the strength and direction of floral evolution. To fully understand and predict the evolutionary trajectories of floral traits, it is critical to disentangle the direct and indirect effects of floral traits on plant fitness in natural populations. We experimentally quantified phenotypic selection on floral traits through female fitness and estimated the casual effects of nectar robbing with different nectar robbing intensities on trait-fitness relationships in both the L- (long-style and short-anther phenotype) and S-morph (short-style and long-anther phenotype) flowers among Primula secundiflora populations. A larger number of flowers and wider corolla tubes had both direct and indirect positive effects on female fitness in the P. secundiflora populations. The indirect effects of these two traits on female fitness were mediated by nectar robbers. The indirect effect of the number of flowers on female fitness increased with increasing nectar robbing intensity. In most populations, the direct and/or indirect effects of floral traits on female fitness were stronger in the S-morph flowers than in the L-morph flowers. In addition, nectar robbers had a direct positive effect on female fitness, but this effect varied between the L- and S-morph flowers. These results show the potential role of nectar robbers in influencing the trait-fitness relationships in this primrose species.


Assuntos
Flores/anatomia & histologia , Aptidão Genética , Néctar de Plantas , Primula/anatomia & histologia , Flores/fisiologia , Aptidão Genética/fisiologia , Fenótipo , Néctar de Plantas/fisiologia , Polinização/fisiologia , Primula/fisiologia
7.
Nat Commun ; 10(1): 2017, 2019 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-31043615

RESUMO

Sexual selection has manifold ecological and evolutionary consequences, making its net effect on population fitness difficult to predict. A powerful empirical test is to experimentally manipulate sexual selection and then determine how population fitness evolves. Here, we synthesise 459 effect sizes from 65 experimental evolution studies using meta-analysis. We find that sexual selection on males tends to elevate the mean and reduce the variance for many fitness traits, especially in females and in populations evolving under stressful conditions. Sexual selection had weaker effects on direct measures of population fitness such as extinction rate and proportion of viable offspring, relative to traits that are less closely linked to population fitness. Overall, we conclude that the beneficial population-level consequences of sexual selection typically outweigh the harmful ones and that the effects of sexual selection can differ between sexes and environments. We discuss the implications of these results for conservation and evolutionary biology.


Assuntos
Evolução Biológica , Aptidão Genética/fisiologia , Preferência de Acasalamento Animal/fisiologia , Seleção Genética/fisiologia , Animais , Conservação dos Recursos Naturais/métodos , Feminino , Masculino
8.
Nat Commun ; 10(1): 68, 2019 01 08.
Artigo em Inglês | MEDLINE | ID: mdl-30622246

RESUMO

Steady-state protein abundance is set by four rates: transcription, translation, mRNA decay and protein decay. A given protein abundance can be obtained from infinitely many combinations of these rates. This raises the question of whether the natural rates for each gene result from historical accidents, or are there rules that give certain combinations a selective advantage? We address this question using high-throughput measurements in rapidly growing cells from diverse organisms to find that about half of the rate combinations do not exist: genes that combine high transcription with low translation are strongly depleted. This depletion is due to a trade-off between precision and economy: high transcription decreases stochastic fluctuations but increases transcription costs. Our theory quantitatively explains which rate combinations are missing, and predicts the curvature of the fitness function for each gene. It may guide the design of gene circuits with desired expression levels and noise.


Assuntos
Regulação da Expressão Gênica/fisiologia , Aptidão Genética/fisiologia , Modelos Genéticos , RNA Mensageiro/metabolismo , Animais , Biologia Computacional , Conjuntos de Dados como Assunto , Escherichia coli , Redes Reguladoras de Genes/fisiologia , Genoma/genética , Ensaios de Triagem em Larga Escala , Humanos , Camundongos , Biossíntese de Proteínas/genética , Estabilidade de RNA/genética , Saccharomyces cerevisiae , Transcrição Genética/genética
9.
Mol Ecol ; 28(6): 1394-1411, 2019 03.
Artigo em Inglês | MEDLINE | ID: mdl-30633410

RESUMO

Genetic divergence among populations arises through natural selection or drift and is counteracted by connectivity and gene flow. In sympatric populations, isolating mechanisms are thus needed to limit the homogenizing effects of gene flow to allow for adaptation and speciation. Chromosomal inversions act as an important mechanism maintaining isolating barriers, yet their role in sympatric populations and divergence with gene flow is not entirely understood. Here, we revisit the question of whether inversions play a role in the divergence of connected populations of the marine fish Atlantic cod (Gadus morhua), by exploring a unique data set combining whole-genome sequencing data and behavioural data obtained with acoustic telemetry. Within a confined fjord environment, we find three genetically differentiated Atlantic cod types belonging to the oceanic North Sea population, the western Baltic population and a local fjord-type cod. Continuous behavioural tracking over 4 year revealed temporally stable sympatry of these types within the fjord. Despite overall weak genetic differentiation consistent with high levels of gene flow, we detected significant frequency shifts of three previously identified inversions, indicating an adaptive barrier to gene flow. In addition, behavioural data indicated that North Sea cod and individuals homozygous for the LG12 inversion had lower fitness in the fjord environment. However, North Sea and fjord-type cod also occupy different depths, possibly contributing to prezygotic reproductive isolation and representing a behavioural barrier to gene flow. Our results provide the first insights into a complex interplay of genomic and behavioural isolating barriers in Atlantic cod and establish a new model system towards an understanding of the role of genomic structural variants in adaptation and diversification.


Assuntos
Inversão Cromossômica/genética , Gadus morhua/genética , Fluxo Gênico/genética , Seleção Genética/genética , Animais , Deriva Genética , Aptidão Genética/fisiologia , Variação Genética/genética , Homozigoto , Isolamento Reprodutivo , Simpatria/genética
10.
PLoS One ; 13(12): e0207131, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30517134

RESUMO

Reproductive site selection is a key determinant of fitness in many taxa. However, if the site characteristics that enhance offspring survival are detrimental to the parent's survival or mating success, then complex evolutionary trade-offs occur. In the Brazilian Atlantic Forest, males of the treefrog species Aparasphenodon arapapa use the temporary water bodies in forest-floor bromeliads to court and mate. Males fit tightly into the plant with the head blocking the access and after mating, stay in the bromeliad with the offspring. Since evaporation of the temporary water body inside the bromeliad results in reproductive failure, we expected that males would simply choose the largest bromeliad tanks with the most water. We found that although this was generally true, males seemed to avoid both very large bromeliads and very high water volumes. Field observations suggested a trade-off mechanism for this pattern, whereby very large and water-filled tanks would reduce the male's ability to effectively seal the tank entrance, avoid predation, or call to mating females. Males also avoided bromeliads with leaf litter and preferred slightly inclined plants. Our results indicate that during reproductive site selection, this bromeliad-breeder needs to engage in complex trade-offs between selection pressures, balancing water requirements against the need for defense and potentially, the ability to attract a mate.


Assuntos
Anuros/fisiologia , Aptidão Genética/fisiologia , Comportamento Sexual Animal/fisiologia , Animais , Evolução Biológica , Brasil , Bromelia , Feminino , Florestas , Masculino , Reprodução/fisiologia
11.
Proc Natl Acad Sci U S A ; 115(45): 11549-11554, 2018 11 06.
Artigo em Inglês | MEDLINE | ID: mdl-30348792

RESUMO

Human-dominated landscapes represent one of the most rapidly expanding and least-understood ecosystems on earth. Yet, we know little about which features in these landscapes promote sustainable wildlife populations. Historically, in urban areas, landowners have converted native plant communities into habitats dominated by nonnative species that are not susceptible to pest damage and require little maintenance. However, nonnative plants are also poor at supporting insects that are critical food resources for higher order consumers. Despite the logical connection, no study has examined the impact of nonnative plants on subsequent population responses of vertebrate consumers. Here, we demonstrate that residential yards dominated by nonnative plants have lower arthropod abundance, forcing resident Carolina chickadees (Poecile carolinensis) to switch diets to less preferred prey and produce fewer young, or forgo reproduction in nonnative sites altogether. This leads to lower reproductive success and unsustainable population growth in these yards compared with those with >70% native plant biomass. Our results reveal that properties landscaped with nonnative plants function as population sinks for insectivorous birds. To promote sustainable food webs, urban planners and private landowners should prioritize native plant species.


Assuntos
Artrópodes/fisiologia , Cadeia Alimentar , Insetívoros/fisiologia , Espécies Introduzidas , Passeriformes/fisiologia , Reprodução/fisiologia , Animais , Artrópodes/classificação , Tamanho da Ninhada , Conservação dos Recursos Naturais , District of Columbia , Ecossistema , Aptidão Genética/fisiologia , Longevidade , Plantas
12.
Sci Rep ; 8(1): 15346, 2018 10 18.
Artigo em Inglês | MEDLINE | ID: mdl-30337588

RESUMO

The recent nomination by the World Health Organization of Acinetobacter baumannii as the number one priority pathogen for the development of new antibiotics is a direct consequence of its fast evolution of pathogenicity, and in particular of multidrug resistance. While the development of new antibiotics is critical, understanding the mechanisms behind the crescent bacterial antibiotic resistance is equally relevant. Often, resistance and other bacterial virulence elements are contained on highly mobile pieces of DNA that can easily spread to other bacteria. Prophages are one of the mediators of this form of gene transfer, and have been frequently found in bacterial genomes, often offering advantageous features to the host. Here we assess the contribution of prophages for the evolution of A. baumannii pathogenicity. We found prophages to be notably diverse and widely disseminated in A. baumannii genomes. Also remarkably, A. baumannii prophages encode for multiple putative virulence factors that may be implicated in the bacterium's capacity to colonize host niches, evade the host immune system, subsist in unfavorable environments, and tolerate antibiotics. Overall our results point towards a significant contribution of prophages for the dissemination and evolution of pathogenicity in A. baumannii, and highlight their clinical relevance.


Assuntos
Acinetobacter baumannii/patogenicidade , Acinetobacter baumannii/virologia , Variação Genética , Prófagos/genética , Virulência/genética , Acinetobacter baumannii/genética , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Farmacorresistência Bacteriana/genética , Aptidão Genética/fisiologia , Tamanho do Genoma , Genoma Bacteriano , Genoma Viral , Interações Hospedeiro-Patógeno/genética , Sequências Repetitivas Dispersas , Proteoma/genética , Proteoma/metabolismo
13.
Sci Rep ; 8(1): 9695, 2018 06 26.
Artigo em Inglês | MEDLINE | ID: mdl-29946077

RESUMO

Sexual selection allows male individuals to adopt different evolutionary strategies in mating system. In this study, we determined whether dominance affected reproductive fitness of male crickets Velarifictorus aspersus during both pre-copulatory and post-copulatory selection when we excluded male-male competition. The results showed that females mated more often with male winners only during the first 2 h after a fight when male winners were more likely to produce courtship songs than losers. However, females did not retain the attached spermatophores of male winners longer than those of male losers, and the fecundity and fertilization success also did not differ significantly between females mated different times with male winners and losers. Instead, the fertilization success was positively correlated with male body weight. These results suggest that a recent wining experience increases reproductive fitness of males during pre-copulatory selection, but females may prefer larger males rather than winners during post-copulatory selection. The incoordination between pre- and post-copulatory selection may allow males to adopt different evolutionary strategies in mating system.


Assuntos
Gryllidae/fisiologia , Comportamento Sexual Animal/fisiologia , Animais , Feminino , Fertilidade/fisiologia , Aptidão Genética/fisiologia , Masculino , Reprodução/fisiologia
14.
Am J Bot ; 105(5): 943-949, 2018 05.
Artigo em Inglês | MEDLINE | ID: mdl-29797579

RESUMO

PREMISE OF THE STUDY: Organisms engage in multiple species interactions simultaneously. While pollination studies generally focus on plants and pollinators exclusively, secondary robbing, a behavior that requires other species (primary robbers) to first create access holes in corollas, is common. It has been shown that secondary robbing can reduce plants' female fitness; however, we lack knowledge about its impact on male plant fitness. METHODS: We experimentally simulated primary and secondary robbing in the monocarpic perennial Ipomopsis aggregata (Polemoniaceae), quantifying indirect effects on pollinator-mediated pollen (dye) donation. We also assessed whether continual nectar removal via the floral opening has similar effects on hummingbird-pollinator behavior as continual secondary robbing through robber holes. KEY RESULTS: We found no significant indirect effects of secondary robbing on a component of Ipomopsis male fitness. Although robbing did reduce pollen (dye) donation due to avoidance of robbed plants by pollinating hummingbirds, pollen donation did not differ between the two robbing treatments. The effects of secondary robbing on hummingbird behavior resembled effects of chronic nectar removal by pollinators. Our results indicate that hummingbird pollinators may use a combination of cues, including cues given by the presence or absence of nectar, to make foraging decisions. CONCLUSIONS: Combined with prior research, this study suggests that secondary robbing is less costly to a component of male fitness than to female fitness in Ipomopsis, broadening our knowledge of the overall costs of mutualism exploitation to total plant fitness.


Assuntos
Ericales/fisiologia , Aptidão Genética/fisiologia , Néctar de Plantas/fisiologia , Polinização , Animais , Aves/fisiologia , Ericales/genética , Comportamento Alimentar , Flores/fisiologia , Reprodução
15.
Curr Biol ; 28(6): 902-914.e5, 2018 03 19.
Artigo em Inglês | MEDLINE | ID: mdl-29526590

RESUMO

Biological sex, a fundamental dimension of internal state, can modulate neural circuits to generate behavioral variation. Understanding how and why circuits are tuned by sex can provide important insights into neural and behavioral plasticity. Here we find that sexually dimorphic behavioral responses to C. elegans ascaroside sex pheromones are implemented by the functional modulation of shared chemosensory circuitry. In particular, the sexual state of a single sensory neuron pair, ADF, determines the nature of an animal's behavioral response regardless of the sex of the rest of the body. Genetic feminization of ADF causes males to be repelled by, rather than attracted to, ascarosides, whereas masculinization of ADF has the opposite effect in hermaphrodites. When ADF is ablated, both sexes are weakly repelled by ascarosides. Genetic sex modulates ADF function by tuning chemosensation: although ADF is functional in both sexes, it detects the ascaroside ascr#3 only in males, a consequence of cell-autonomous action of the master sexual regulator tra-1. This occurs in part through the conserved DM-domain gene mab-3, which promotes the male state of ADF. The sexual modulation of ADF has a key role in reproductive fitness, as feminization or ablation of ADF renders males unable to use ascarosides to locate mates. Our results reveal an economical mechanism in which sex-specific behavioral valence arises through the cell-autonomous regulation of a chemosensory switch by genetic sex, allowing a social cue with salience for both sexes to elicit navigational responses commensurate with the differing needs of each.


Assuntos
Aptidão Genética/fisiologia , Células Receptoras Sensoriais/fisiologia , Animais , Comportamento Animal/fisiologia , Caenorhabditis elegans/metabolismo , Proteínas de Caenorhabditis elegans/metabolismo , Proteínas de Caenorhabditis elegans/fisiologia , Células Quimiorreceptoras/metabolismo , Proteínas de Ligação a DNA/metabolismo , Proteínas de Ligação a DNA/fisiologia , Feminino , Masculino , Sistema Nervoso , Neurônios/fisiologia , Células Receptoras Sensoriais/metabolismo , Atrativos Sexuais/metabolismo , Caracteres Sexuais , Comportamento Sexual Animal/fisiologia , Fatores de Transcrição/genética
16.
Proc Biol Sci ; 285(1875)2018 03 28.
Artigo em Inglês | MEDLINE | ID: mdl-29593113

RESUMO

Microbial genotypes with similarly high proficiency at a cooperative behaviour in genetically pure groups often exhibit fitness inequalities caused by social interaction in mixed groups. Winning competitors in this scenario have been referred to as 'cheaters' in some studies. Such interaction-specific fitness inequalities, as well as social exploitation (in which interaction between genotypes increases absolute fitness), might evolve due to selection for competitiveness at the focal behaviour or might arise non-adaptively due to pleiotropy, hitchhiking or genetic drift. The bacterium Myxococcus xanthus sporulates during cooperative development of multicellular fruiting bodies. Using M. xanthus lineages that underwent experimental evolution in allopatry without selection on sporulation, we demonstrate that interaction-specific fitness inequalities and facultative social exploitation during development readily evolved indirectly among descendant lineages. Fitness inequalities between evolved genotypes were not caused by divergence in developmental speed, as faster-developing strains were not over-represented among competition winners. In competitions between ancestors and several evolved strains, all evolved genotypes produced more spores than the ancestors, including losers of evolved-versus-evolved competitions, indicating that adaptation in non-developmental contexts pleiotropically increased competitiveness for spore production. Overall, our results suggest that fitness inequalities caused by social interaction during cooperative processes may often evolve non-adaptively in natural populations.


Assuntos
Adaptação Fisiológica , Evolução Biológica , Aptidão Genética/fisiologia , Myxococcus xanthus/fisiologia , Intervalos de Confiança , Farmacorresistência Bacteriana/genética , Farmacorresistência Bacteriana/fisiologia , Deleção de Genes , Aptidão Genética/genética , Genótipo , Myxococcus xanthus/genética , Rifampina/metabolismo , Esporos Bacterianos
17.
Evolution ; 72(5): 1034-1049, 2018 05.
Artigo em Inglês | MEDLINE | ID: mdl-29522254

RESUMO

Phenotypic plasticity is thought to impact evolutionary trajectories by shifting trait values in a direction that is either favored by natural selection ("adaptive" plasticity) or disfavored ("nonadaptive" plasticity). However, it is unclear how commonly each of these types of plasticity occurs in natural populations. To answer this question, we measured glucosinolate defensive chemistry and reproductive fitness in over 1500 individuals of the wild perennial mustard Boechera stricta, planted in four common gardens across central Idaho, United States. Glucosinolate profiles-including total glucosinolate concentration as well as the relative abundances and overall diversity of different compounds-were strongly plastic both among habitats and within habitats. Patterns of glucosinolate plasticity varied greatly among genotypes. Plasticity among sites was predicted to affect fitness in 27.1% of cases; more often than expected by chance, glucosinolate plasticity increased rather than decreased relative fitness. In contrast, we found no evidence for within-habitat selection on glucosinolate reaction norm slopes (i.e., plasticity along a continuous environmental gradient). Together, our results indicate that glucosinolate plasticity may improve the ability of B. stricta populations to persist after migration to new habitats.


Assuntos
Adaptação Fisiológica , Evolução Biológica , Brassicaceae/metabolismo , Brassicaceae/genética , Ecossistema , Aptidão Genética/fisiologia , Genótipo , Glucosinolatos/metabolismo , Idaho , Fenótipo
18.
Proc Natl Acad Sci U S A ; 115(10): 2425-2430, 2018 Mar 06.
Artigo em Inglês | MEDLINE | ID: mdl-29453274

RESUMO

Assays to accurately estimate relative fitness of bacteria growing in multistrain communities can advance our understanding of how selection shapes diversity within a lineage. Here, we present a variant of the "evolve and resequence" approach both to estimate relative fitness and to identify genetic variants responsible for fitness variation of symbiotic bacteria in free-living and host environments. We demonstrate the utility of this approach by characterizing selection by two plant hosts and in two free-living environments (sterilized soil and liquid media) acting on synthetic communities of the facultatively symbiotic bacterium Ensifer meliloti We find (i) selection that hosts exert on rhizobial communities depends on competition among strains, (ii) selection is stronger inside hosts than in either free-living environment, and (iii) a positive host-dependent relationship between relative strain fitness in multistrain communities and host benefits provided by strains in single-strain experiments. The greatest changes in allele frequencies in response to plant hosts are in genes associated with motility, regulation of nitrogen fixation, and host/rhizobia signaling. The approach we present provides a powerful complement to experimental evolution and forward genetic screens for characterizing selection in bacterial populations, identifying gene function, and surveying the functional importance of naturally occurring genomic variation.


Assuntos
Aptidão Genética , Medicago , Sinorhizobium meliloti , Microbiologia do Solo , Simbiose , Fenômenos Fisiológicos Bacterianos , Aptidão Genética/genética , Aptidão Genética/fisiologia , Variação Genética , Medicago/microbiologia , Medicago/fisiologia , Fixação de Nitrogênio , Fenótipo , Rizoma/microbiologia , Sinorhizobium meliloti/genética , Sinorhizobium meliloti/fisiologia , Biologia Sintética
19.
Biol Lett ; 14(2)2018 02.
Artigo em Inglês | MEDLINE | ID: mdl-29438052

RESUMO

In primitively eusocial insects, many individuals function as workers despite being capable of independent reproduction. Such altruistic behaviour is usually explained by the argument that workers gain indirect fitness by helping close genetic relatives. The focus on indirect fitness has left open the question of whether workers are also capable of getting direct fitness in the future in spite of working towards indirect fitness in the present. To investigate this question, we recorded behavioural profiles of all wasps on six naturally occurring nests of Ropalidia marginata, and then isolated all wasps in individual plastic boxes, giving them an opportunity to initiate nests and lay eggs. We found that 41% of the wasps successfully did so. Compared to those that failed to initiate nests, those that did were significantly younger, had significantly higher frequency of self-feeding behaviour on their parent nests but were not different in the levels of work performed in the parent nests. Thus ageing and poor feeding, rather than working for their colonies, constrain individuals for future independent reproduction. Hence, future direct fitness and present work towards gaining indirect fitness are not incompatible, making it easier for worker behaviour to be selected by kin selection or multilevel selection.


Assuntos
Comportamento Animal/fisiologia , Aptidão Genética/fisiologia , Vespas/fisiologia , Animais , Comportamento Alimentar , Feminino , Comportamento Social
20.
FEMS Microbiol Ecol ; 94(2)2018 02 01.
Artigo em Inglês | MEDLINE | ID: mdl-29293955

RESUMO

Escherichia coli colonizes various body parts of animal hosts as a commensal and a pathogen. It can also persist in the external environment in the absence of fecal pollution. It remains unclear how this species has evolved to adapt to such contrasting habitats. Lysogeny plays pivotal roles in the diversification of the phenotypic and ecologic characters of E. coli as a symbiont. We hypothesized that lysogeny could also confer fitness to survival in the external environment. To test this hypothesis, we used the induced phages of an E. coli strain originating from marine sediment to infect a fecal E. coli strain to obtain an isogenic lysogen of the latter. The three strains were tested for survivorship in microcosms of seawater, marine sediment and sediment interstitial water as well as swimming motility, glycogen accumulation, biofilm formation, substrate utilization and stress resistance. The results indicate that lysogenic infection led to tractable changes in many of the ecophysiological attributes tested. Particularly, the lysogen had better survivorship in the microcosms and had a substrate utilization profile resembling the sediment strain more than the wild type fecal strain. Our findings provide new insights into the understanding of how E. coli survives in the natural environment.


Assuntos
Bacteriófagos/genética , Escherichia coli/genética , Escherichia coli/virologia , Aptidão Genética/genética , Aptidão Genética/fisiologia , Lisogenia/genética , Animais , Proteínas de Escherichia coli/genética , Fezes/microbiologia , Genoma Bacteriano/genética , Sedimentos Geológicos/microbiologia , Água do Mar/microbiologia , Suínos/microbiologia
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