Heritable symbiosis: The advantages and perils of an evolutionary rabbit hole

Many eukaryotes have obligate associations with microorganisms that are transmitted directly between generations. A model for heritable symbiosis is the association of aphids, a clade of sap-feeding insects, and Buchnera aphidicola, a gammaproteobacterium that colonized an aphid ancestor 150 million years ago and persists in almost all 5,000 aphid species. Symbiont acquisition enables evolutionary and ecological expansion; aphids are one of many insect groups that would not exist without heritable symbiosis. Receiving less attention are potential negative ramifications of symbiotic alliances. In the short run, symbionts impose metabolic costs. Over evolutionary time, hosts evolve dependence beyond the original benefits of the symbiosis. Symbiotic partners enter into an evolutionary spiral that leads to irreversible codependence and associated risks. Host adaptations to symbiosis (e.g., immune-system modification) may impose vulnerabilities. Symbiont genomes also continuously accumulate deleterious mutations, limiting their beneficial contributions and environmental tolerance. Finally, the fitness interests of obligate heritable symbionts are distinct from those of their hosts, leading to selfish tendencies. Thus, genes underlying the host–symbiont interface are predicted to follow a coevolutionary arms race, as observed for genes governing host–pathogen interactions. On the macroevolutionary scale, the rapid evolution of interacting symbiont and host genes is predicted to accelerate host speciation rates by generating genetic incompatibilities. However, degeneration of symbiont genomes may ultimately limit the ecological range of host species, potentially increasing extinction risk. Recent results for the aphid–Buchnera symbiosis and related systems illustrate that, whereas heritable symbiosis can expand ecological range and spur diversification, it also presents potential perils.

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Microbe Profile: Buchnera aphidicola: ancient aphid accomplice and endosymbiont exemplar

Microbiology ◽

10.1099/mic.0.001127 ◽

2021 ◽

Vol 167 (12) ◽

Author(s):

Nancy A. Moran

Keyword(s):

Type Species ◽

Rapid Evolution ◽

Essential Amino Acids ◽

Aphid Species ◽

Buchnera Aphidicola ◽

Content Type ◽

Link Type ◽

Phylogenetic Reconstructions ◽

Gene Acquisition ◽

Conserved Gene

Buchnera aphidicola is an obligate endosymbiont of aphids that cannot be cultured outside of hosts. It exists as diverse strains in different aphid species, and phylogenetic reconstructions show that it has been maternally transmitted in aphids for >100 million years. B. aphidicola genomes are highly reduced and show conserved gene order and no gene acquisition, but encoded proteins undergo rapid evolution. Aphids depend on B. aphidicola for biosynthesis of essential amino acids and as an integral part of embryonic development. How B. aphidicola populations are regulated within hosts remains little known.

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THE IMPACT OF MONEY ON OUTPUT IN CZECH REPUBLIC AND ROMANIA

Journal of Business Economics and Management ◽

10.3846/jbem.2018.1480 ◽

2018 ◽

Vol 19 (1) ◽

pp. 20-41 ◽

Cited By ~ 2

Author(s):

Mihaela SIMIONESCU ◽

Adam P. BALCERZAK ◽

Yuriy BILAN ◽

Anna KOTÁSKOVÁ

Keyword(s):

Czech Republic ◽

Global Financial Crisis ◽

Causality Test ◽

Developed Country ◽

Developed Economies ◽

Long Run ◽

Short Run ◽

Almost All ◽

Vector Error Correction Models ◽

The Impact

The problem of relationship between output and money has become again a subject of special interests of economists after the most recent global financial crisis and monetary stabilization policies applied by central banks of almost all developed economies. In this context, the main aim of this paper is to assess the relation between GDP and the most important monetary variables in two countries: Romania and Czech Republic over the period of 1995:Q1 – 2015:Q4. The choice of these economies was deliberate. The selected countries are different from the viewpoint of rate and results of transformation from the centrally planned to market economy, which have influenced their current economic environment stability. Czech Republic is currently classified as middle or even developed country, whereas Romania is still considered as a developing economy. Thus, differences between these two countries make them interesting in the case of comparative studies. In the empirical part of our research the vector error correction models (VECM) were applied. The main findings of the article are the following: in Romania, there is a short-run causality from money supply (M3) to GDP and a long-run relationship between GDP, internal credit and M3. According to Granger causality test, the rate of M3 in Romania was a cause for economic. In Czech Republic, there is a short-run causality from M3 to GDP and a long-run causality between GDP, internal credit and M3. Thus, the results contradict the money neutrality hypothesis in post-transformation Central European economies.

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Climate cooling and clade competition likely drove the decline of lamniform sharks

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1902693116 ◽

2019 ◽

Vol 116 (41) ◽

pp. 20584-20590 ◽

Cited By ~ 10

Author(s):

Fabien L. Condamine ◽

Jules Romieu ◽

Guillaume Guinot

Keyword(s):

Evolutionary Biology ◽

Extinction Risk ◽

Research Question ◽

Apex Predators ◽

Extinction Rates ◽

Extant Species ◽

Speciation Rates ◽

Sister Relationships ◽

Abiotic And Biotic Factors ◽

Climate Cooling

Understanding heterogeneity in species richness between closely related clades is a key research question in ecology and evolutionary biology. Multiple hypotheses have been proposed to interpret such diversity contrasts across the tree of life, with most studies focusing on speciation rates to explain clades’ evolutionary radiations, while often neglecting extinction rates. Here we study a notorious biological model as exemplified by the sister relationships between mackerel sharks (Lamniformes, 15 extant species) and ground sharks (Carcharhiniformes, ∼290 extant species). Using a comprehensive fossil dataset, we found that the diversity dynamics of lamniforms waxed and waned following repeated cycles of radiation phases and declining phases. Radiation phases peaked up to 3 times the current diversity in the early Late Cretaceous. In the last 20 million years, the group declined to its present-day diversity. Along with a higher extinction risk for young species, we further show that this declining pattern is likely attributed to a combination of abiotic and biotic factors, with a cooling-driven extinction (negative correlation between temperature and extinction) and clade competition with some ground sharks. Competition from multiple clades successively drove the demise and replacement of mackerel sharks due to a failure to originate facing the rise of ground sharks, particularly since the Eocene. These effects came from ecologically similar carcharhiniform species inhibiting diversification of medium- and large-sized lamniforms. These results imply that the interplay between abiotic and biotic drivers had a substantial role in extinction and speciation, respectively, which determines the sequential rise and decline of marine apex predators.

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On the link between HIV prevalence and health expenditure: an asymmetric analysis

Journal of Economic Studies ◽

10.1108/jes-12-2018-0420 ◽

2020 ◽

Vol 47 (3) ◽

pp. 509-526

Author(s):

Massomeh Hajilee ◽

Mahsa Oroojeni Mohammad Javad ◽

Linda A. Hayes

Keyword(s):

Health Expenditure ◽

Developed Countries ◽

Hiv Prevalence ◽

Content Type ◽

Nonlinear Ardl ◽

Long Run ◽

Short Run ◽

Linear And Nonlinear ◽

Almost All ◽

Hiv Aids

PurposeIndividuals' health is considered one of the major determinants of higher levels of productivity and economic development. Over the past century, the widespread occurrence of human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) has been a serious threat to economic development around the globe and has caused a dramatic fall in the life expectancy rate in many nations. This is the first study that examines the impact of HIV prevalence on health expenditure at the national level employing two linear and nonlinear autoregressive distributed lag (ARDL) models and simultaneously tests the long-run and short-run relationship for five selected developed countries. The authors employ annual data from 1981 to 2016. They find that HIV prevalence has a significant impact on health expenditure in the short-run and long-run in all five countries using the linear model and four of the countries in the nonlinear model. They find that HIV/AIDS prevalence has a significant short-run and long-run asymmetric impact on health expenditure of almost all selected developed economies.Design/methodology/approachThe authors are employing two linear and nonlinear ARDL models and simultaneously test the long-run and short-run relationship for five selected developed countries.FindingsThe authors find that HIV/AIDS prevalence has a significant short-run and long-run asymmetric impact on health expenditure of almost all selected developed economies.Originality/valueTo the best of the authors’ knowledge, this is the first research work that empirically examines the link between HIV prevalence and health expenditure for this group of countries using linear and nonlinear ARDL approach for short run and long run.

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How humans drive speciation as well as extinction

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2016.0600 ◽

2016 ◽

Vol 283 (1833) ◽

pp. 20160600 ◽

Cited By ~ 28

Author(s):

J. W. Bull ◽

M. Maron

Keyword(s):

Species Diversity ◽

Human Activities ◽

Rapid Evolution ◽

Novel Ecosystem ◽

No Net Loss ◽

Extinction Rates ◽

Trade Offs ◽

Speciation Rates ◽

Nuanced Understanding ◽

Comparable Magnitude

A central topic for conservation science is evaluating how human activities influence global species diversity. Humanity exacerbates extinction rates. But by what mechanisms does humanity drive the emergence of new species? We review human-mediated speciation, compare speciation and known extinctions, and discuss the challenges of using net species diversity as a conservation objective. Humans drive rapid evolution through relocation, domestication, hunting and novel ecosystem creation—and emerging technologies could eventually provide additional mechanisms. The number of species relocated, domesticated and hunted during the Holocene is of comparable magnitude to the number of observed extinctions. While instances of human-mediated speciation are known, the overall effect these mechanisms have upon speciation rates has not yet been quantified. We also explore the importance of anthropogenic influence upon divergence in microorganisms. Even if human activities resulted in no net loss of species diversity by balancing speciation and extinction rates, this would probably be deemed unacceptable. We discuss why, based upon ‘no net loss’ conservation literature—considering phylogenetic diversity and other metrics, risk aversion, taboo trade-offs and spatial heterogeneity. We conclude that evaluating speciation alongside extinction could result in more nuanced understanding of biosphere trends, clarifying what it is we actually value about biodiversity.

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Lack of signal for the impact of venom gene diversity on speciation rates in cone snails

10.1101/359976 ◽

2018 ◽

Author(s):

Mark A Phuong ◽

Michael E Alfaro ◽

Gusti N Mahardika ◽

Ristiyanti M Marwoto ◽

Romanus Edy Prabowo ◽

...

Keyword(s):

Gene Diversity ◽

Rapid Evolution ◽

Limiting Factor ◽

Exon Capture ◽

Speciation Rates ◽

Intrinsic Capacity ◽

Cone Snails ◽

Species Specific ◽

Capture Techniques ◽

The Impact

AbstractUnderstanding why some groups of organisms are more diverse than others is a central goal in macroevolution. Evolvability, or lineages’ intrinsic capacity for evolutionary change, is thought to influence disparities in species diversity across taxa. Over macroevolutionary time scales, clades that exhibit high evolvability are expected to have higher speciation rates. Cone snails (family: Conidae, >900 spp.) provide a unique opportunity to test this prediction because their venom genes can be used to characterize differences in evolvability between clades. Cone snails are carnivorous, use prey-specific venom (conotoxins) to capture prey, and the genes that encode venom are known and diversify through gene duplication. Theory predicts that higher gene diversity confers a greater potential to generate novel phenotypes for specialization and adaptation. Therefore, if conotoxin gene diversity gives rise to varying levels of evolvability, conotoxin gene diversity should be coupled with macroevolutionary speciation rates. We applied exon capture techniques to recover phylogenetic markers and conotoxin loci across 314 species, the largest venom discovery effort in a single study. We paired a reconstructed timetree using 12 fossil calibrations with species-specific estimates of conotoxin gene diversity and used trait-dependent diversification methods to test the impact of evolvability on diversification patterns. Surprisingly, did not detect any signal for the relationship between conotoxin gene diversity and speciation rates, suggesting that venom evolution may not be the rate-limiting factor controlling diversification dynamics in Conidae. Comparative analyses showed some signal for the impact of diet and larval dispersal strategy on diversification patterns, though whether or not we detected a signal depended on the dataset and the method. If our results remain true with increased sampling in future studies, they suggest that the rapid evolution of Conidae venom may cause other factors to become more critical to diversification, such as ecological opportunity or traits that promote isolation among lineages.

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Methylation at CpG sites in genomes of aphid Acyrtosiphon pisum and its endosymbiont Buchnera

10.1101/2021.08.26.457790 ◽

2021 ◽

Author(s):

Mathilde Clement ◽

Martine Da Rocha ◽

Sandra Agnel ◽

Guenter Raddatz ◽

Alain Robichon ◽

...

Keyword(s):

Dna Methylation ◽

Buchnera Aphidicola ◽

Low Level ◽

Endosymbiotic Bacteria ◽

Whole Genomes ◽

Dna Methylase ◽

Mutualistic Relationship ◽

Sap Feeding ◽

Methyl Cytosine ◽

Methylation Patterns

Pea aphid Acyrtosiphon pisum, a sap-feeding insect, has established a mutualistic relationship with an endosymbiotic bacteria (Buchnera aphidicola) that constitutes an evolutionary successful symbiosis to synthetize complex chemical compounds from a nutrient deprived diet. In this study, led by the presence of DNMT1 and a putative DNMT3 methylase in the aphid genome, we investigated the distribution of the methyl groups on 5'cytosine in CpG motifs on the whole genomes of host and endosymbiont, and looked into their correlation with gene expression. The DNA methylation turned to be present at low level in aphid (around 3% of total genomic cytosine) compared to mammals and plants, but increased to ~9% in genes. Interestingly, the reduced genome of the endosymbiont Buchnera also shows global low level of methyl cytosine despite the fact that its genome does not shelter any DNA methylase. This finding argues for the import of DNA methylase from the host to the endosymbiont. The observed differences in methylation patterns between two clonal variants (host plus endosymbiont) are reported along with the differences in their transcriptome profiles. Our data allowed to decipher a dynamic combinatorial DNA methylation and epigenetic cross talk between host and symbiont in a clonality context that might count for the aphid adaptation to environment.

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Does evolution of plumage patterns and of migratory behaviour in Apodini swifts (Aves: Apodiformes) follow distributional range shifts?

10.7287/peerj.preprints.797v1 ◽

2015 ◽

Cited By ~ 1

Author(s):

Dieter Thomas Tietze ◽

Michael Wink ◽

Martin Päckert

Keyword(s):

Phylogenetic Signal ◽

Visual Signals ◽

Long Distance ◽

Old World ◽

Distributional Range ◽

Speciation Rates ◽

The One ◽

Almost All ◽

The Tropics ◽

Old World Tropics

The Apodini swifts in the Old World serve as an example for a recent radiation on an intercontinental scale on the one hand. On the other hand they provide a model for the interplay of trait and distributional range evolution with speciation, extinction and trait transition rates on a low taxonomic level (23 extant taxa). Swifts are well adapted to a life mostly in the air and to long-distance movements. Their overall colouration is dull, but lighter feather patches of chin and rump stand out as visual signals. Only few Apodini taxa breed outside the tropics; they are the only species in the study group that migrate long distances to wintering grounds in the tropics and subtropics. We reconstructed a dated molecular phylogeny including all species, numerous outgroups and fossil constraints. Several methods were used for historical biogeography and two models for the study of trait evolution. We finally correlated trait expression with geographic status. The differentiation of the Apodini took place in less than 9 Ma. Their ancestral range most likely comprised large parts of the Old-World tropics, although the majority of extant taxa breed in the Afrotropic and the closest relatives occur in the Indomalayan. The expression of all three investigated traits increased speciation rates and the traits were more likely lost than gained. Chin patches are found in almost all species, so that no association with phylogeny or range could be found. Rump patches showed a phylogenetic signal and were correlated with Indomalayan distribution. Apodini swifts performed long-distance migration whenever they expanded their range to temperate latitudes during warm periods, repeatedly in the Pleistocene.

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Island Colonization: The Origin and Development of Island Communities

Pacific Conservation Biology ◽

10.1071/pc090075 ◽

2009 ◽

Vol 15 (1) ◽

pp. 75

Author(s):

Jarrad Cousin

Keyword(s):

Island Biogeography ◽

Extinction Risk ◽

Island Colonization ◽

Island Communities ◽

Theory Of Island Biogeography ◽

Successional Stages ◽

Ideal Study ◽

Volcanic Islands ◽

Almost All ◽

Study Unit

The theory of island biogeography revolutionized the study of island colonization and extinction. Since its inception in the 1960?s, it has allowed scientists and historians alike to understand reasons for patterns of species distributions on islands, as well as assisting conservation managers to model extinction risk of species populations on isolated islands. Volcanic islands represent a ?tabula rasa?, or clean slate for the study of island biogeography, as invariably, resultant volcanic activity decimates almost all observable life. As such, they form the ideal study unit for examining colonization of islands. The Krakatua eruption of 1883 is such an example, with the resultant blasts scouring the Krakatua islands of almost all life, thus allowing scientists to track the colonisation and successional stages that followed. Another example is Surtsey Island, which emerged from the sea 40 km south of Iceland in 1963. It represented a unique opportunity to examine colonization of a previously non-existent and thus uninhabited island. Given that there are many influences and avenues governing the origin and colonization of life on islands, Island Colonization: The Origin and Development of Island Communities, edited by Tim New, represents an important book compiling information on this topic.

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MISTR: A conserved MItochondrial STress Response network revealed by signatures of evolutionary conflict

10.1101/2020.01.25.919811 ◽

2020 ◽

Author(s):

Mahsa Sorouri ◽

Tyron Chang ◽

Palmy Jesudhasan ◽

Chelsea Pinkham ◽

Nels C. Elde ◽

...

Keyword(s):

Electron Transport Chain ◽

Rapid Evolution ◽

Biological Processes ◽

Algal Virus ◽

Evolutionary Conflict ◽

Transport Chain ◽

Response Network ◽

Stress Signals ◽

Genetic Signatures ◽

Host Genes

ABSTRACTHost-pathogen conflicts leave genetic signatures of variation in homologous host genes. Using these “molecular scars” as a guide, we discovered a vertebrate-specific MItochondrial STress Response circuit (MISTR). MISTR proteins are associated with electron transport chain factors and activated by stress signals such as interferon-gamma and hypoxia. Upon stress, ultraconserved miRNAs downregulate MISTR1 followed by replacement with paralogs MISTR AntiViral (MISTRAV) or MISTR Hypoxia (MISTRH), depending on the insult. While cells lacking MISTR1 are more sensitive to apoptotic triggers, cells lacking MISTRAV or expressing the poxvirus-encoded vMISTRAV exhibit resistance to the same insults. Rapid evolution signatures across primate genomes for MISTR1 and MISTRAV indicate ancient and ongoing conflicts with pathogens. MISTR proteins are also found in plants, yeasts, and an algal virus indicating ancient origins and suggesting diverse means of altering mitochondrial function under stress. The discovery of MISTR circuitry highlights the use of evolution-guided studies to reveal fundamental biological processes.

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