scholarly journals Increased pollination specialization did not increase corolla shape constraints in Antillean plants

2016 ◽  
Author(s):  
Simon Joly ◽  
François Lambert ◽  
Hermine Alexandre ◽  
Julien Clavel ◽  
Étienne Léveillé-Bourret ◽  
...  
Keyword(s):  
Structural Variation ◽  
Reproductive Organs ◽  
Evolutionary Constraints ◽  
Evolutionary Models ◽  
Relaxed Selection ◽  
Generalist Species ◽  
Evolutionary Forces ◽  
Pollination Strategy ◽  
Effective Pollinators ◽  
Generalist Pollination

AbstractFlowers show important structural variation as reproductive organs but the evolutionary forces underlying this diversity are still poorly understood. In animal-pollinated species, flower shape is strongly fashioned by selection imposed by pollinators, which is expected to vary according to guilds of effective pollinators. Using the Antillean subtribe Gesneriinae (Gesneriaceae), we tested the hypothesis that pollination specialists pollinated by one functional type of pollinator have maintained more similar corolla shapes through time due to stronger selection constraints compared to species with more generalist pollination strategies. Using geometric morphometrics and evolutionary models, we showed that the corolla of hummingbird specialists, bat specialists, and species with a mixed-pollination strategy (pollinated by hummingbirds and bats; thus a more generalist strategy) have distinct shapes and that these shapes have evolved under evolutionary constraints. However, we did not find support for smaller disparity in corolla shape for hummingbird specialists compared to more generalist species. This could be because the corolla shape of more generalist species in subtribe Gesneriinae, which has evolved multiple times, is finely adapted to be effectively pollinated by both bats and hummingbirds. These results suggest that pollination generalization is not necessarily associated with relaxed selection constraints.

scholarly journals Active Site-Induced Evolutionary Constraints Follow Fold Polarity Principles in Soluble Globular Enzymes

2019 ◽  
Vol 36 (8) ◽  
pp. 1728-1733 ◽  
Author(s):  
Alexander Mayorov ◽  
Matteo Dal Peraro ◽  
Luciano A Abriata
Keyword(s):  
Amino Acid ◽  
Active Sites ◽  
Metabolic Cost ◽  
Evolutionary Rates ◽  
Recent Analysis ◽  
Evolutionary Constraints ◽  
Evolutionary Models ◽  
Data Set ◽  
Soluble Enzymes ◽  
Amino Acid Preference

Abstract A recent analysis of evolutionary rates in >500 globular soluble enzymes revealed pervasive conservation gradients toward catalytic residues. By looking at amino acid preference profiles rather than evolutionary rates in the same data set, we quantified the effects of active sites on site-specific constraints for physicochemical traits. We found that conservation gradients respond to constraints for polarity, hydrophobicity, flexibility, rigidity and structure in ways consistent with fold polarity principles; while sites far from active sites seem to experience no physicochemical constraint, rather being highly variable and favoring amino acids of low metabolic cost. Globally, our results highlight that amino acid variation contains finer information about protein structure than usually regarded in evolutionary models, and that this information is retrievable automatically with simple fits. We propose that analyses of the kind presented here incorporated into models of protein evolution should allow for better description of the physical chemistry that underlies molecular evolution.

scholarly journals The lifetimes of planetary debris discs around white dwarfs

2020 ◽  
Vol 496 (2) ◽  
pp. 2292-2308 ◽  
Author(s):  
Dimitri Veras ◽  
Kevin Heng
Keyword(s):  
Steady State ◽  
White Dwarf ◽  
White Dwarfs ◽  
Input Parameter ◽  
Evolutionary Constraints ◽  
Minor Planets ◽  
Evolutionary Models ◽  
Tidal Disruption ◽  
Different Types ◽  
Break Up

ABSTRACT The lifetime of a planetary disc that orbits a white dwarf represents a crucial input parameter into evolutionary models of that system. Here we apply a purely analytical formalism to estimate lifetimes of the debris phase of these discs, before they are ground down into dust or are subject to sublimation from the white dwarf. We compute maximum lifetimes for three different types of white dwarf discs, formed from (i) radiative YORP break-up of exo-asteroids along the giant branch phases at 2–100 au, (ii) radiation-less spin-up disruption of these minor planets at ${\sim} 1.5\!-\!4.5\, \mathrm{R}_{\odot }$, and (iii) tidal disruption of minor or major planets within about $1.3\, \mathrm{R}_{\odot }$. We display these maximum lifetimes as a function of disc mass and extent, constituent planetesimal properties, and representative orbital excitations of eccentricity and inclination. We find that YORP discs with masses of up to 1024 kg live long enough to provide a reservoir of surviving cm-sized pebbles and m- to km-sized boulders that can be perturbed intact to white dwarfs with cooling ages of up to 10 Gyr. Debris discs formed from the spin or tidal disruption of these minor planets or major planets can survive in a steady state for up to, respectively, 1 or 0.01 Myr, although most tidal discs would leave a steady state within about 1 yr. Our results illustrate that dust-less planetesimal transit detections are plausible, and would provide particularly robust evolutionary constraints. Our formalism can easily be adapted to individual systems and future discoveries.

scholarly journals Evaluating the role of reproductive constraints in ant social evolution

2010 ◽  
Vol 365 (1540) ◽  
pp. 617-630 ◽  
Author(s):  
Abderrahman Khila ◽  
Ehab Abouheif
Keyword(s):  
Germ Cell ◽  
Social Evolution ◽  
Alternative Hypothesis ◽  
Reproductive Organs ◽  
Division Of Labour ◽  
Cell Development ◽  
Germ Cell Development ◽  
Evolutionary Forces ◽  
Selection Framework

The reproductive division of labour is a key feature of eusociality in ants, where queen and worker castes show dramatic differences in the development of their reproductive organs. To understand the developmental and genetic basis underlying this division of labour, we performed a molecular analysis of ovary function and germ cell development in queens and workers. We show that the processes of ovarian development in queens have been highly conserved relative to the fruitfly Drosophila melanogaster . We also identify specific steps during oogenesis and embryogenesis in which ovarian and germ cell development have been evolutionarily modified in the workers. These modifications, which we call ‘reproductive constraints’, are often assumed to represent neutral degenerations that are a consequence of social evolutionary forces. Based on our developmental and functional analysis of these constraints, however, we propose and discuss the alternative hypothesis that reproductive constraints represent adaptive proximate mechanisms or traits for maintaining social harmony in ants. We apply a multi-level selection framework to help understand the role of these constraints in ant social evolution. A complete understanding of how cooperation, conflict and developmental systems evolve in social groups requires a ‘socio-evo-devo’ approach that integrates social evolutionary and developmental biology.

scholarly journals A non-adaptive demographic mechanism for genome expansion in Streptomyces

2021 ◽  
Author(s):  
Mallory J Choudoir ◽  
Marko J Järvenpää ◽  
Pekka Marttinen ◽  
Daniel H Buckley
Keyword(s):  
Genome Size ◽  
Range Expansion ◽  
Population Expansion ◽  
Intermediate Frequency ◽  
Microbial Genome ◽  
Gene Gain ◽  
Relaxed Selection ◽  
Evolutionary Forces ◽  
Genome Expansion ◽  
Large Genomes

AbstractThe evolution of microbial genome size is driven by gene acquisition and loss events that occur at scales from individual genomes to entire pangenomes. The equilibrium between gene gain and loss is shaped by evolutionary forces, including selection and drift, which are in turn influenced by population demographics. There is a well-known bias towards deletion in microbial genomes, which promotes genome streamlining. Less well described are mechanisms that promote genome expansion, giving rise to the many microbes, such as Streptomyces, that have unusually large genomes. We find evidence of genome expansion in Streptomyces sister-taxa, and we hypothesize that a recent demographic range expansion drove increases in genome size through a non-adaptive mechanism. These Streptomyces sister-taxa, NDR (northern-derived) and SDR (southern-derived), represent recently diverged lineages that occupy distinct geographic ranges. Relative to SDR genomes, NDR genomes are larger, have more genes, and their genomes are enriched in intermediate frequency genes. We also find evidence of relaxed selection in NDR genomes relative to SDR genomes. We hypothesize that geographic range expansion, coupled with relaxed selection, facilitated the introgression of non-adaptive horizontally acquired genes, which accumulated at intermediate frequencies through a mechanism known as genome surfing. We show that similar patterns of pangenome structure and genome expansion occur in a simulation that models the effects of population expansion on genome dynamics. We show that non-adaptive evolutionary phenomena can explain expansion of microbial genome size, and suggest that this mechanism might explain why some bacteria with large genomes can be found in soil.

scholarly journals Can constraint closure provide a generalized understanding of community dynamics in ecosystems?

2020 ◽  
Author(s):  
Steven L. Peck ◽  
Andrew Heiss
Keyword(s):  
Pattern Formation ◽  
Simulation Model ◽  
Community Dynamics ◽  
Species Turnover ◽  
Evolutionary Constraints ◽  
Computer Simulation Model ◽  
Ecosystem Stability ◽  
Ecological Communities ◽  
Agent Based ◽  
Evolutionary Forces

AbstractSince the inception of the discipline, understanding causal complexity in ecological communities has been a challenge. Here we draw insights from recent work on constraint closure that suggests ways of grappling with ecological complexity that yield generalizable theoretical insights. Using a set of evolutionary constraints on species flow through ecological communities, which include: selection, species drift, dispersal, and speciation, combined with multispecies interactions such as mutualistic interactions, and abiotic constraints, we demonstrate how constraint closure allows communities to emerge as semi-autonomous structures. Here we develop an agent-based model to explore how evolutionary constraints provide stability to ecological communities. The model is written in Netlogo, an agent based-modeling system, with advanced tools for manipulating spatially structured models and tools for tracking pattern formation. We articulate ways that ecological pattern formation, viewed through the lens of constraint closure, informs questions about stability and turnover in community ecology. The role of the chosen constraints was clear from the simulation results. It took the shape of both inducing stability and creating conditions for a more dynamic community with increases in species turnover through time. Key ecological and evolutionary variables showed overall stability in the landscape structure when plotted against the number of constraints, suggesting that these evolutionary forces act as constraints to the flow of species in such a way that constraint closure is achieved effecting semi-autonomy.Author SummaryEcosystems are among the most complex structures studied. They comprise elements that seem both stable and contingent. The stability of these systems depends on interactions among their evolutionary history, including the accidents of organisms moving through the landscape and microhabitats of the earth, and the biotic and abiotic conditions in which they occur. When ecosystems are stable, how is that achieved? Here we look at ecosystem stability through a computer simulation model that suggests that it may depend on what constrains the system and how those constraints are structured. Specifically, if the constraints found in an ecological community form a closed loop, that allows particular kinds of feedback may give structure to the ecosystem processes for a period of time. In this simulation model, we look at how evolutionary forces act in such a way these closed constraint loops may form. This may explain some kinds of ecosystem stability. This work will also be valuable to ecological theorists in understanding general ideas of stability in such systems.

scholarly journals Pseudofinder: detection of pseudogenes in prokaryotic genomes

2021 ◽  
Author(s):  
Mitch J Syberg-Olsen ◽  
Arkadiy I Garber ◽  
Patrick J Keeling ◽  
John McCutcheon ◽  
Filip Husnik
Keyword(s):  
Open Source Software ◽  
Evolutionary Dynamics ◽  
Population Bottlenecks ◽  
Relaxed Selection ◽  
Substantial Fraction ◽  
Evolutionary Forces ◽  
Functional Potential ◽  
Prokaryotic Genomes ◽  
Ecological Shifts ◽  
Inactivating Mutations

Prokaryotic genomes are generally gene dense and encode relatively few pseudogenes, or nonfunctional/inactivated remnants of genes. However, in certain contexts, such as recent ecological shifts or extreme population bottlenecks (such as those experienced by symbionts and pathogens), pseudogenes can quickly accumulate and form a substantial fraction of the genome. Identification of pseudogenes is, thus, a critical step for understanding the evolutionary forces acting upon, and the functional potential encoded within, prokaryotic genomes. Here, we present Pseudofinder, an open-source software dedicated to pseudogene identification and analysis. With Pseudofinder's multi-pronged, reference-based approach, we demonstrate its capacity to detect a wide variety of pseudogenes, including those that are highly degraded and typically missed by gene-calling pipelines, as well newly formed pseudogenes, which can have only one or a few inactivating mutations. Additionally, Pseudofinder can detect intact genes undergoing relaxed selection, which may indicate incipient pseudogene formation. Implementation of Pseudofinder in annotation pipelines will not only clarify the functional potential of sequenced microbes, but will also generate novel insights and hypotheses regarding the evolutionary dynamics of bacterial and archaeal genomes.

scholarly journals Evolutionary modelling of HCV subtypes provides rationale for their different disease outcomes

2021 ◽  
Author(s):  
Hang Zhang ◽  
Ahmed A. Quadeer ◽  
Matthew R. McKay
Keyword(s):  
Hepatocellular Carcinoma ◽  
Envelope Glycoprotein ◽  
Chronic Infection ◽  
Fitness Landscape ◽  
Antibody Responses ◽  
Evolutionary Constraints ◽  
Evolutionary Models ◽  
Disease Outcomes ◽  
Distinct Disease ◽  
Subtype 1B

AbstractHepatitis C virus (HCV) is a leading cause of liver-associated disease and liver cancer. Of the major HCV subtypes, patients infected with subtype 1b have been associated with having a higher risk of developing chronic infection, cirrhosis and hepatocellular carcinoma. However, underlying reasons for this increased disease severity remain unknown. Here, we provide an evolutionary rationale, based on a comparative study of fitness landscape and in-host evolutionary models of the envelope glycoprotein 2 (E2) of HCV subtypes 1a and 1b. Our analysis demonstrates that a higher chronicity rate of subtype 1b may be attributed to lower fitness constraints, enabling 1b viruses to more easily escape antibody responses. More generally, our results suggest that differences in evolutionary constraints between HCV subtypes may be an important factor in mediating distinct disease outcomes. Our analysis also identifies antibodies that appear to be escape-resistant against both subtypes 1a and 1b, providing directions for the design of HCV vaccines having cross-subtype protection.

scholarly journals Genetic and Non-Genetic Mechanisms Underlying Cancer Evolution

Cancers ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 1380
Author(s):  
Yelyzaveta Shlyakhtina ◽  
Katherine L. Moran ◽  
Maximiliano M. Portal
Keyword(s):  
Cancer Biology ◽  
Current Knowledge ◽  
Genetic Networks ◽  
Cancer Development ◽  
Evolutionary Models ◽  
Cancer Evolution ◽  
Evolutionary Forces ◽  
Core Concepts ◽  
Genetic Mechanisms ◽  
Evolutionary Paths

Cancer development can be defined as a process of cellular and tissular microevolution ultimately leading to malignancy. Strikingly, though this concept has prevailed in the field for more than a century, the precise mechanisms underlying evolutionary processes occurring within tumours remain largely uncharacterized and rather cryptic. Nevertheless, although our current knowledge is fragmentary, data collected to date suggest that most tumours display features compatible with a diverse array of evolutionary paths, suggesting that most of the existing macro-evolutionary models find their avatar in cancer biology. Herein, we discuss an up-to-date view of the fundamental genetic and non-genetic mechanisms underlying tumour evolution with the aim of concurring into an integrated view of the evolutionary forces at play throughout the emergence and progression of the disease and into the acquisition of resistance to diverse therapeutic paradigms. Our ultimate goal is to delve into the intricacies of genetic and non-genetic networks underlying tumour evolution to build a framework where both core concepts are considered non-negligible and equally fundamental.

Ultrastructural aspects of gymnosperms reproductive organs tissues due to their functional condition

1978 ◽  
Vol 36 (2) ◽  
pp. 440-441
Author(s):  
G. M. Kozubov
Keyword(s):  
Metabolic Activity ◽  
Functional Condition ◽  
Reproductive Organs ◽  
Considerable Change ◽  
Complicated Structure ◽  
Tetrad Stage ◽  
Ubisch Bodies ◽  
Similar Organization ◽  
Female Reproductive Organs ◽  
High Metabolic Activity

The ultrastructure of reproductive organs of pine, spruce, larch and ginkgo was investigated. It was found that the male reproductive organs possess similar organization. The most considerable change in the ultrastructure of the microsporocytes occur in meiosis. Sporoderm is being laid at the late tetrad stage. The cells of the male gameto-phyte are distinguished according to the metabolic activity of the or- ganells. They are most weakly developed in the spermiogenic cell. Ta-petum of the gymnosperms is of the periplasmodic - secretorial type. The Ubisch bodies which possess similar structure in the types investigated but are specific in details in different species are produced in tapetum.Parietal and subepidermal layers are distinguished for their high metabolic activity and are capable of the autonomous photosynthesis. Female reproductive organs differ more greatly in their struture and have the most complicated structure in primitive groups. On the first stages of their formation the inner cells of nucellus are transformed into the nucellar tapetum in which the structures similar to the Ubisch bodies taking part in the formation of the sporoderm of female gametophyte have been found.

Pelvic Impairments

2018 ◽  
Vol 23 (4) ◽  
pp. 9-10
Author(s):  
James Talmage ◽  
Jay Blaisdell
Keyword(s):  
Pelvic Ring ◽  
Reproductive Organs ◽  
High Impact ◽  
Pelvic Fractures ◽  
Motor Dysfunction ◽  
Impact Event ◽  
Concomitant Injuries ◽  
Rating Process ◽  
Pass Through ◽  
A Minor

Abstract Pelvic fractures are relatively uncommon, and in workers’ compensation most pelvic fractures are the result of an acute, high-impact event such as a fall from a roof or an automobile collision. A person with osteoporosis may sustain a pelvic fracture from a lower-impact injury such as a minor fall. Further, major parts of the bladder, bowel, reproductive organs, nerves, and blood vessels pass through the pelvic ring, and traumatic pelvic fractures that result from a high-impact event often coincide with damaged organs, significant bleeding, and sensory and motor dysfunction. Following are the steps in the rating process: 1) assign the diagnosis and impairment class for the pelvis; 2) assign the functional history, physical examination, and clinical studies grade modifiers; and 3) apply the net adjustment formula. Because pelvic fractures are so uncommon, raters may be less familiar with the rating process for these types of injuries. The diagnosis-based methodology for rating pelvic fractures is consistent with the process used to rate other musculoskeletal impairments. Evaluators must base the rating on reliable data when the patient is at maximum medical impairment and must assess possible impairment from concomitant injuries.

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