scholarly journals Convergent evolution of complex structures for ant–bacterial defensive symbiosis in fungus-farming ants

2018 ◽  
Vol 115 (42) ◽  
pp. 10720-10725 ◽  
Author(s):  
Hongjie Li ◽  
Jeffrey Sosa-Calvo ◽  
Heidi A. Horn ◽  
Mônica T. Pupo ◽  
Jon Clardy ◽  
...  
Keyword(s):  
Full Range ◽  
Critical Role ◽  
Ancestral State ◽  
Bacterial Symbionts ◽  
Behavioral Traits ◽  
Direct Observations ◽  
Attine Ants ◽  
Evolutionary Trajectories ◽  
Anatomical Adaptations ◽  
Caste Differences

Evolutionary adaptations for maintaining beneficial microbes are hallmarks of mutualistic evolution. Fungus-farming “attine” ant species have complex cuticular modifications and specialized glands that house and nourish antibiotic-producing Actinobacteria symbionts, which in turn protect their hosts’ fungus gardens from pathogens. Here we reconstruct ant–Actinobacteria evolutionary history across the full range of variation within subtribe Attina by combining dated phylogenomic and ultramorphological analyses. Ancestral-state analyses indicate the ant–Actinobacteria symbiosis arose early in attine-ant evolution, a conclusion consistent with direct observations of Actinobacteria on fossil ants in Oligo-Miocene amber. qPCR indicates that the dominant ant-associated Actinobacteria belong to the genus Pseudonocardia. Tracing the evolutionary trajectories of Pseudonocardia-maintaining mechanisms across attine ants reveals a continuum of adaptations. In Myrmicocrypta species, which retain many ancestral morphological and behavioral traits, Pseudonocardia occur in specific locations on the legs and antennae, unassociated with any specialized structures. In contrast, specialized cuticular structures, including crypts and tubercles, evolved at least three times in derived attine-ant lineages. Conspicuous caste differences in Pseudonocardia-maintaining structures, in which specialized structures are present in worker ants and queens but reduced or lost in males, are consistent with vertical Pseudonocardia transmission. Although the majority of attine ants are associated with Pseudonocardia, there have been multiple losses of bacterial symbionts and bacteria-maintaining structures in different lineages over evolutionary time. The early origin of ant–Pseudonocardia mutualism and the multiple evolutionary convergences on strikingly similar anatomical adaptations for maintaining bacterial symbionts indicate that Pseudonocardia have played a critical role in the evolution of ant fungiculture.

scholarly journals The Diversity and Evolution of Sex Chromosomes in Frogs

Genes ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 483
Author(s):  
Wen-Juan Ma ◽  
Paris Veltsos
Keyword(s):  
Sex Determination ◽  
Sex Chromosomes ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Comparative Genomic ◽  
Ancestral State ◽  
Heteromorphic Sex Chromosomes ◽  
Genomic Studies ◽  
Evolutionary Trajectories ◽  
Heterogametic Sex

Frogs are ideal organisms for studying sex chromosome evolution because of their diversity in sex chromosome differentiation and sex-determination systems. We review 222 anuran frogs, spanning ~220 Myr of divergence, with characterized sex chromosomes, and discuss their evolution, phylogenetic distribution and transitions between homomorphic and heteromorphic states, as well as between sex-determination systems. Most (~75%) anurans have homomorphic sex chromosomes, with XY systems being three times more common than ZW systems. Most remaining anurans (~25%) have heteromorphic sex chromosomes, with XY and ZW systems almost equally represented. There are Y-autosome fusions in 11 species, and no W-/Z-/X-autosome fusions are known. The phylogeny represents at least 19 transitions between sex-determination systems and at least 16 cases of independent evolution of heteromorphic sex chromosomes from homomorphy, the likely ancestral state. Five lineages mostly have heteromorphic sex chromosomes, which might have evolved due to demographic and sexual selection attributes of those lineages. Males do not recombine over most of their genome, regardless of which is the heterogametic sex. Nevertheless, telomere-restricted recombination between ZW chromosomes has evolved at least once. More comparative genomic studies are needed to understand the evolutionary trajectories of sex chromosomes among frog lineages, especially in the ZW systems.

scholarly journals Mountain colonisation, miniaturisation and ecological evolution in a radiation of direct-developing New Guinea Frogs (Choerophryne, Microhylidae)

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3077 ◽  
Author(s):  
Paul M. Oliver ◽  
Amy Iannella ◽  
Stephen J. Richards ◽  
Michael S.Y. Lee
Keyword(s):  
Body Size ◽  
Small Body ◽  
Strong Support ◽  
New Guinea ◽  
Ancestral State ◽  
Tropical Mountains ◽  
Climatic Oscillations ◽  
Evolutionary Trajectories ◽  
Montane Biodiversity ◽  
Male Calling

AimsMountain ranges in the tropics are characterised by high levels of localised endemism, often-aberrant evolutionary trajectories, and some of the world’s most diverse regional biotas. Here we investigate the evolution of montane endemism, ecology and body size in a clade of direct-developing frogs (Choerophryne,Microhylidae) from New Guinea.MethodsPhylogenetic relationships were estimated from a mitochondrial molecular dataset using Bayesian and maximum likelihood approaches. Ancestral state reconstruction was used to infer the evolution of elevational distribution, ecology (indexed by male calling height), and body size, and phylogenetically corrected regression was employed to examine the relationships between these three traits.ResultsWe obtained strong support for a monophyletic lineage comprising the majority of taxa sampled. Within this clade we identified one subclade that appears to have diversified primarily in montane habitats of the Central Cordillera (>1,000 m a.s.l.), with subsequent dispersal to isolated North Papuan Mountains. A second subclade (characterised by moderately to very elongated snouts) appears to have diversified primarily in hill forests (<1,000 m a.s.l.), with inferred independent upwards colonisations of isolated montane habitats, especially in isolated North Papuan Mountains. We found no clear relationship between extremely small body size (adult SVL less than 15 mm) and elevation, but a stronger relationship with ecology—smaller species tend to be more terrestrial.ConclusionsOrogeny and climatic oscillations have interacted to generate high montane biodiversity in New Guinea via both localised diversification within montane habitats (centric endemism) and periodic dispersal across lowland regions (eccentric endemism). The correlation between extreme miniaturisation and terrestrial habits reflects a general trend in frogs, suggesting that ecological or physiological constraints limit niche usage by miniaturised frogs, even in extremely wet environments such as tropical mountains.

scholarly journals Mountain colonisation, miniaturisation and ecological evolution in a radiation of direct developing New Guinea Frogs (Choerophryne, Microhylidae)

2017 ◽  
Author(s):  
Paul M Oliver ◽  
Amy Iannella ◽  
Stephen J Richards ◽  
Michael S.Y Lee
Keyword(s):  
Body Size ◽  
Small Body ◽  
Strong Support ◽  
New Guinea ◽  
Ancestral State ◽  
Tropical Mountains ◽  
Climatic Oscillations ◽  
Evolutionary Trajectories ◽  
Montane Biodiversity ◽  
Male Calling

Aims. Mountain ranges in the tropics are characterised by high levels of localised endemism, often-aberrant evolutionary trajectories, and some of the world’s most diverse regional biotas. Here we investigate the evolution of montane endemism, ecology and body size in a clade of direct-developing frogs (Choerophryne, Microhylidae) from New Guinea. Methods. Phylogenetic relationships were estimated from a mitochondrial molecular dataset using Bayesian and maximum likelihood approaches. Ancestral state reconstruction was used to infer the evolution of elevational distribution, ecology (indexed by male calling height), and body size, and phylogenetically corrected regression was employed to examine the relationships between these three traits. Results. We obtained strong support for a monophyletic lineage comprising the majority of taxa sampled. Within this clade we identified one subclade that appears to have diversified primarily in montane habitats of the Central Cordillera (> 1000 m. a.s.l), with subsequent dispersal to isolated North Papuan Mountains. A second subclade (characterised by moderately to very elongated snouts) appears to have diversified primarily in hill forests (< 1000 m a.s.l.), with inferred independent upwards colonisations of isolated montane habitats, especially in isolated North Papuan Mountains. We found no clear relationship between extremely small body size (adult SVL less than 15mm) and elevation, but a stronger relationship with ecology – smaller species tend to be more terrestrial. Conclusions. Orogeny and climatic oscillations have interacted to generate high montane biodiversity in New Guinea via both localised diversification within montane habitats (centric endemism) and periodic dispersal across lowland regions (eccentric endemism). The correlation between extreme miniaturisation and terrestrial habits reflects a general trend in frogs, suggesting that ecological or physiological constraints limit niche usage by miniaturised frogs, even in extremely wet environments such as tropical mountains.

scholarly journals Behavioral syndromes shape evolutionary trajectories via conserved genetic architecture

2019 ◽  
Author(s):  
Raphael Royauté ◽  
Ann Hedrick ◽  
Ned A. Dochtermann
Keyword(s):  
Genetic Architecture ◽  
Behavioral Syndromes ◽  
Behavioral Syndrome ◽  
Cellular Mechanisms ◽  
Genetic Covariance ◽  
Behavioral Traits ◽  
Field Crickets ◽  
Evolutionary Changes ◽  
Evolutionary Trajectories ◽  
Gryllus Integer

AbstractBehaviors are often correlated within broader syndromes, creating the potential for evolution in one behavior to drive evolutionary changes in other behaviors. Despite demonstrations that behavioral syndromes are common across taxa, whether this potential for evolutionary effects is realized has not yet been demonstrated. Here we show that populations of field crickets (Gryllus integer) exhibit a genetically conserved behavioral syndrome structure despite differences in average behaviors. We found that the distribution of genetic variation and genetic covariance among behavioral traits was consistent with genes and cellular mechanisms underpinning behavioral syndromes rather than correlated selection. Moreover, divergence among populations’ average behaviors was constrained by the genetically conserved behavioral syndrome. Our results demonstrate that a conserved genetic architecture linking behaviors has shaped the evolutionary trajectories of populations in disparate environments—illustrating an important way by which behavioral syndromes result in shared evolutionary fates.

scholarly journals Fossil hominin shoulders support an African ape-like last common ancestor of humans and chimpanzees

2015 ◽  
Vol 112 (38) ◽  
pp. 11829-11834 ◽  
Author(s):  
Nathan M. Young ◽  
Terence D. Capellini ◽  
Neil T. Roach ◽  
Zeresenay Alemseged
Keyword(s):  
Tool Use ◽  
High Speed ◽  
Common Ancestor ◽  
Modern Human ◽  
Last Common Ancestor ◽  
Ancestral State ◽  
Evolutionary Trajectories ◽  
Parsimonious Model ◽  
And Function ◽  
Fossil Hominin

Reconstructing the behavioral shifts that drove hominin evolution requires knowledge of the timing, magnitude, and direction of anatomical changes over the past ∼6–7 million years. These reconstructions depend on assumptions regarding the morphotype of the Homo–Pan last common ancestor (LCA). However, there is little consensus for the LCA, with proposed models ranging from African ape to orangutan or generalized Miocene ape-like. The ancestral state of the shoulder is of particular interest because it is functionally associated with important behavioral shifts in hominins, such as reduced arboreality, high-speed throwing, and tool use. However, previous morphometric analyses of both living and fossil taxa have yielded contradictory results. Here, we generated a 3D morphospace of ape and human scapular shape to plot evolutionary trajectories, predict ancestral morphologies, and directly test alternative evolutionary hypotheses using the hominin fossil evidence. We show that the most parsimonious model for the evolution of hominin shoulder shape starts with an African ape-like ancestral state. We propose that the shoulder evolved gradually along a single morphocline, achieving modern human-like configuration and function within the genus Homo. These data are consistent with a slow, progressive loss of arboreality and increased tool use throughout human evolution.

scholarly journals Beyond brain size

2017 ◽  
Author(s):  
Corina J Logan ◽  
Shahar Avin ◽  
Neeltje Boogert ◽  
Andrew Buskell ◽  
Fiona R. Cross ◽  
...  
Keyword(s):  
Brain Size ◽  
Size Variation ◽  
Brain Evolution ◽  
Simple Relationship ◽  
Cognitive Significance ◽  
Cognitive Measures ◽  
Behavioral Complexity ◽  
Behavioral Traits ◽  
Evolutionary Trajectories ◽  
Brain Behavior

AbstractDespite prolonged interest in comparing brain size and behavioral proxies of ‘intelligence’ across taxa, the adaptive and cognitive significance of brain size variation remains elusive. Central to this problem is the continued focus on hominid cognition as a benchmark, and the assumption that behavioral complexity has a simple relationship with brain size. Although comparative studies of brain size have been criticized for not reflecting how evolution actually operates, and for producing spurious, inconsistent results, the causes of these limitations have received little discussion. We show how these issues arise from implicit assumptions about what brain size measures and how it correlates with behavioral and cognitive traits. We explore how inconsistencies can arise through heterogeneity in evolutionary trajectories and selection pressures on neuroanatomy or neurophysiology across taxa. We examine how interference from ecological and life history variables complicates interpretations of brain-behavior correlations, and point out how this problem is exacerbated by the limitations of brain and cognitive measures. These considerations, and the diversity of brain morphologies and behavioral capacities, suggest that comparative brain-behavior research can make greater progress by focusing on specific neuroanatomical and behavioral traits within relevant ecological and evolutionary contexts. We suggest that a synergistic combination of the ‘bottom up’ approach of classical neuroethology and the ‘top down’ approach of comparative biology/psychology within closely related but behaviorally diverse clades can limit the effects of heterogeneity, interference, and noise. We argue this shift away from broad-scale analyses of superficial phenotypes will provide deeper, more robust insights into brain evolution.

scholarly journals Olfactory receptor repertoire size in dinosaurs

2019 ◽  
Vol 286 (1904) ◽  
pp. 20190909 ◽  
Author(s):  
Graham M. Hughes ◽  
John A. Finarelli
Keyword(s):  
Olfactory Receptor ◽  
Ecological Niches ◽  
Ancestral State ◽  
Repertoire Size ◽  
Receptor Repertoire ◽  
Olfactory Acuity ◽  
Sensory Evolution ◽  
Evolutionary Trajectories ◽  
Or Gene ◽  
Or Genes

The olfactory bulb (OB) ratio is the size of the OB relative to the cerebral hemisphere, and is used to estimate the proportion of the forebrain devoted to smell. In birds, OB ratio correlates with the number of olfactory receptor (OR) genes and therefore has been used as a proxy for olfactory acuity. By coupling OB ratios with known OR gene repertoires in birds, we infer minimum repertoire sizes for extinct taxa, including non-avian dinosaurs, using phylogenetic modelling, ancestral state reconstruction and comparative genomics. We highlight a shift in the scaling of OB ratio to body size along the lineage leading to modern birds, demonstrating variable OR repertoires present in different dinosaur and crown-bird lineages, with varying factors potentially influencing sensory evolution in theropods. We investigate the ancestral sensory space available to extinct taxa, highlighting potential adaptations to ecological niches. Through combining morphological and genomic data, we show that, while genetic information for extinct taxa is forever lost, it is potentially feasible to investigate evolutionary trajectories in extinct genomes.

Directors’ Perceptions of Board Effectiveness and Internal Operations

2021 ◽  
Author(s):  
J. Yo-Jud Cheng ◽  
Boris Groysberg ◽  
Paul Healy ◽  
Rajesh Vijayaraghavan
Keyword(s):  
Full Range ◽  
Critical Role ◽  
Relative Strength ◽  
Future Research ◽  
Corporate Boards ◽  
Board Effectiveness ◽  
Public Firms ◽  
Public Data ◽  
Performance Effects ◽  
Internal Operations

We contribute to the growing literature on the effectiveness of corporate boards by examining the effect of two insights that have been largely unexplored in prior studies that use public data. First, since boards’ responsibilities are wide-ranging, more holistic performance measures may better capture the full range of their duties than specific public actions and outcomes (e.g., disclosure of risk management processes, financial restatements, acquisition returns, CEO turnover). And second, because corporate boards share many characteristics of other types of teams, their effectiveness is likely to be influenced by their internal operations. To examine the performance effects of these insights, we use data from 577 directors of U.S. public firms that responded to a survey we conducted in 2015–2016 and qualitative data from interviews of 75 directors. Our study establishes a strong relation between director perceptions of board performance effectiveness and internal board operations. Further, by highlighting the critical role of internal operations, identifying areas of relative strength and weakness in boards’ effectiveness in various activities, and probing director perceptions of their primary responsibilities, we are able to offer concrete suggestions for future research on board effectiveness. This paper was accepted by Shiva Rajgopal, accounting.

The dawn of Molecular Genetics in Paleoceanography: tracing Arctic change during the Holocene with marine sedaDNA records from Greenland

2020 ◽  
Author(s):  
Sofia Ribeiro ◽  
Sara Hardardottir ◽  
Jessica Louise Ray ◽  
Stijn De Schepper ◽  
Audrey Limoges ◽  
...  
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Full Range ◽  
Sediment Cores ◽  
Critical Role ◽  
Genetic Material ◽  
Digital Pcr ◽  
The Arctic ◽  
Taxonomic Resolution ◽  
Gene Copy

&lt;p&gt;As we move towards a &amp;#8220;blue&amp;#8221; Arctic Ocean in the summer within the next decades, predicting the full range of effects of climate change on the marine arctic environment remains a challenge. This is partly due to the paucity of long-term data on ocean-biosphere-cryosphere interactions over time and partly because, today, much of our knowledge on past ocean variability derives from microfossil and biogeochemical tracers that all have considerable limitations such as preservation biases and low taxonomic resolution or coverage.&lt;/p&gt;&lt;p&gt;Recent studies have revealed sedaDNA as a potential &amp;#8220;game-changer&amp;#8221; in our ability to reconstruct past ocean conditions, due to the preservation of DNA at low temperatures, and the possibility to capture a much larger fraction of the Arctic marine biome diversity than with classical approaches. However, while sedaDNA has been used in terrestrial, archeological, and lake studies for some years, its application to marine sediment records is still in its infancy.&lt;/p&gt;&lt;p&gt;Here, we will present new results from material recently collected along the two Arctic Ocean outflow shelves off Greenland (Greenland Sea/Fram Strait and Northern Baffin Bay/Nares Strait). We have used a combination of modern and ancient DNA methods applied to seawater, surface sediments, and sediment cores covering the past ca. 12 000 years with the objectives of: 1) characterizing the vertical export of sea ice-associated genetic material through the water column and into the sediments following sea ice melt and 2) exploring the potential of sedaDNA from the circum-polar sea ice dinoflagellate Polarella glacialis as a new sea ice proxy. For the first objective, we followed a comparative metabarcoding approach while the second objective included designing species-specific primers followed by gene copy number quantification by a droplet digital PCR assay.&amp;#160;&lt;/p&gt;&lt;p&gt;We argue that sedaDNA will have a critical role in expanding the Paleoceanography &amp;#8220;toolbox&amp;#8221; and lead to the establishment of a new cross-disciplinary field.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

The Domestic Politics of Let

2019 ◽  
pp. 149-196
Author(s):  
C. Christine Fair
Keyword(s):  
Domestic Politics ◽  
Full Range ◽  
Critical Role ◽  
The State ◽  
Deep State ◽  
Foreign Policies

Most scholars of Lashkar-e-Tayyaba/Jamaat ud Dawah (LeT/JuD) tend to view the tanzeem as a proxy militia for the Pakistani army. While the organization certainly performs this role, this narrow understanding undervalues the full scope of activities it performs, alongside the full range of political and social perquisites that the organization affords the Pakistani state, and thus, the importance that the state attaches to it. Presumably, the formation of the Milli Muslim League (MML) will further entrench this alliance between the state and the LeT/JuD. This chapter demonstrates that LeT/JuD performs a critical role in assisting the deep state to secure its domestic objectives as well as its foreign policies in India and Afghanistan.

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