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2,225 results for “reversal”
Data from: The enemy of my enemy is my friend: native pine marten recovery reverses the decline of the red squirrel by suppressing grey squirrel populations
Shared enemies may instigate or modify competitive interactions between species. The dis-equilibrium caused by non-native species introductions has revealed that the outcome of such indirect interactions can often be dramatic. However, studies of enemy mediated competition mostly consider the impact of a single enemy, despite species being embedded in complex networks of interactions. Here we demonstrate that native red and invasive grey squirrels in Britain, two terrestrial species linked by resource and disease-mediated apparent competition, are also now linked by a second enemy-mediated relationship involving a shared native predator recovering from historical persecution, the European pine marten. Through combining spatial capture recapture techniques to estimate pine marten density, and squirrel site occupancy data, we find that the impact of exposure to predation is highly asymmetrical, with non-native grey squirrel occupancy strongly negatively affected by exposure to pine martens. In contrast, exposure to pine marten predation has an indirect positive effect on red squirrel populations. Pine marten predation thus reverses the well-documented outcome of resource and apparent competition between red and grey squirrels.
Data from: Competitive reversal between plant species is driven by species-specific tolerance to flooding stress and nutrient acquisition during early marsh succession
1. Understanding plant species interactions along successional trajectories are critical for managing and restoring ecosystems, as both resource availability and abiotic stresses change over time to affect competitive outcomes and species distributions. Newly created ecosystems experience a succession of plants species and rapid changes in resource availability, which may influence the outcome of biotic interactions. How these biotic interactions vary along abiotic gradients in early successional systems is not well understood. 2. Here, we tested the hypothesis that species-specific tolerances to flooding would influence their relative ability to capture resources (i.e., nutrients) and affect competition intensity between pioneer and secondary successional species in an early successional created tidal marsh. We transplanted a competitively dominant higher marsh species, Spartina patens, across an elevation gradient within and outside of clones of a pioneer stress-tolerant low marsh species, Spartina alterniflora. 3. Within six months, Spartina alterniflora had suppressed the stature and growth of S. patens; however, the magnitude of this competitive effect increased at lower marsh elevations where S. alterniflora was more efficient at capturing available nitrogen (N). In unvegetated areas, where S. patens vigor was high, the amount of available N was approximately 40 times greater than within S. alterniflora clones. 4. Synthesis and applications. Our results demonstrate that competition intensity of the stress-tolerant species over the competitive species depended on relative resource capture in response to abiotic stress. Managing for specific vegetation communities in marsh restoration, therefore, requires insight into these relationships and interactions. Specifically, marsh restoration in high nutrient environments will limit the succession to high density competitive species due to competition with stress-tolerant pioneer species, particularly at lower elevations.
Data from: Obesity-induced decreases in muscle performance are not reversed by weight loss
BACKGROUND/OBJECTIVES: Obesity can affect muscle phenotypes, and may thereby constrain movement and energy expenditure. Weight loss is a common and intuitive intervention for obesity, but it is not known whether the effects of obesity on muscle function are reversible by weight loss. Here we tested whether obesity-induced changes in muscle metabolic and contractile phenotypes are reversible by weight loss. SUBJECTS/METHODS: We used zebrafish (Danio rerio) in a factorial design to compare energy metabolism, locomotor capacity, muscle isometric force and work-loop power output, and myosin heavy chain (MHC) composition between lean fish, diet-induced obese fish, and fish that were obese and then returned to lean body mass following diet restriction. RESULTS: Obesity increased resting metabolic rates (Po0.001) and decreased maximal metabolic rates (P = 0.030), but these changes were reversible by weight loss, and were not associated with changes in muscle citrate synthase activity. In contrast, obesity-induced decreases in locomotor performance (P = 0.0034), and isolated muscle isometric stress (P = 0.01), work-loop power output (Po0.001) and relaxation rates (P = 0.012) were not reversed by weight loss. Similarly, obesity-induced decreases in concentrations of fast and slow MHCs, and a shift toward fast MHCs were not reversed by weight loss. CONCLUSION: Obesity-induced changes in locomotor performance and muscle contractile function were not reversible by weight loss. These results show that weight loss alone may not be a sufficient intervention.
Data from: Individual heterogeneity determines sex differences in mortality in a monogamous bird with reversed sexual dimorphism
Sex differences in mortality are pervasive in vertebrates, and usually result in shorter life spans in the larger sex, although the underlying mechanisms are still unclear. On the other hand, differences in frailty among individuals (i.e. individual heterogeneity), can play a major role in shaping demographic trajectories in wild populations. The link between these two processes has seldom been explored. We used Bayesian survival trajectory analysis to study age-specific mortality trajectories in the Eurasian sparrowhawk (Accipiter nisus), a monogamous raptor with reversed sexual size dimorphism. We tested the effect of individual heterogeneity on age-specific mortality, and the extent by which this heterogeneity was determined by average reproductive output and wing length as measures of an individual's frailty. We found that sex differences in age-specific mortality were primarily driven by the differences in individual heterogeneity between the two sexes. Females were more heterogeneous than males in their level of frailty. Thus, a larger number of females with low frailty are able to survive to older ages than males, with life expectancy for the least frail adult females reaching up to 4·23 years, while for the least frail adult males it was of 2·68 years. We found that 50% of this heterogeneity was determined by average reproductive output and wing length in both sexes. For both, individuals with high average reproductive output had also higher chances to survive. However, the effect of wing length was different between the two sexes. While larger females had higher survival, larger males had lower chances to survive. Our results contribute a novel perspective to the ongoing debate about the mechanisms that drive sex differences in vital rates in vertebrates. Although we found that variables that relate to the cost of reproduction and sexual dimorphism are at least partially involved in determining these sex differences, it is through their effect on the level of frailty that they affect age patterns of mortality. Therefore, our results raise the possibility that observed differences in age-specific demographic rates may in fact be driven by differences in individual heterogeneity.
Data from: Biomechanical evaluation of peak reverse torque (PRT) in a dynamic compression plate-screw construct used in a goat tibia segmental defect model
Background Peak reverse torque (PRT) is a valid method to evaluate implants' secondary stability in the healing bone. The secondary stability is achieved by the implant over time and it has been positively correlated with the implants' osseointegration level. In other words, peak reverse torque is the force required to break the bone-implant interface. The purpose of this study was to compare the peak reverse torque for the self-tapping and non-self-tapping screws used in a dynamic compression plate–screw–bone construct after 60 days of loading when used to stabilize 2.5-cm defects in the tibia of goats. The second objective was to compare the peak removal torque of the screws placed in the different positions to evaluate the impact of construct biomechanics on implants osseointegration. Results In total, 176 non-self-tapping screws and 66 self-tapping screws were used to fix the 8-holes dynamic compression plates to the bones. The screws were placed in the tibiae from proximal (position sites 1,2, 3) to distal (position sites 4,5,6) and were removed 60 days post-implantation. The animals remained weight-bearing throughout the study period. The screws placed in the proximal diaphysis had significantly less peak reverse torque than screws placed in the distal diaphysis in both groups (p < 0.05). The peak reverse torque resistance was also significantly less for the non-self-tapping screws as compared with the self-tapping screws (p < 0.05). The intracortical fractures in the trans-cortex occurred significantly more frequently during the placement of non-self-tapping screws (p < 0.05) as compared with self-tapping screws (p < 0.05). Conclusions Based on these results, we concluded that self-tapping screws may be expected to maintain a more stable bone-implant interface during the first 60 days of loading as compared with non-self-tapping screws. This should be a consideration for orthopedic surgeons and scientists using bone plates to stabilize non-load sharing fractures when a stable plate-screw-bone interface is needed to ensure prolonged stability.
Data from: Multiple reversals of bill length over 1.7 million years in a Hawaiian bird lineage
Evolutionary change has been documented over geological time, but reversals in morphology, from an ancestral state to a derived state and back again, tend to be rare. Multiple reversals along the same lineage are even rarer. We use the chronology of the Hawaiian Islands and an avian example, the Hawaiian honeycreeper 'amakihi (Hemignathus spp.) lineage, which originated on the oldest main island of Kaua'i 1.7 million years ago, to examine the process of sequential reversals in bill length. We document three single and two multiple reversals of bill length on six main islands from oldest to youngest, consistent with the phylogeny of the lineage. Longer bills occur on islands with endemic species, including phylogenetically relevant outgroups, that may compete with or dominate the 'amakihi. On islands without those species, the 'amakihi had shorter bills of similar length. Both types of reversals in morphology in this lineage integrate microevolutionary processes with macroevolution in the adaptive radiation of Hawaiian honeycreepers.
Data from: Reverse genetics in the tidepool: knockdown of target gene expression via RNA interference in the copepod Tigriopus californicus
Reverse genetic tools are essential for characterizing phenotypes of novel genes and testing functional hypotheses generated from next-generation sequencing studies. RNA interference (RNAi) has been a widely used technique for describing or quantifying physiological, developmental or behavioural roles of target genes by suppressing their expression. The marine intertidal copepod Tigriopus californicus has become an emerging model for evolutionary and physiological studies, but this species is not amenable to most genetic manipulation approaches. As crustaceans are susceptible to RNAi-mediated gene knock-down, we developed a simple method for delivery of gene-specific double-stranded RNA that results in significant suppression of target gene transcription levels. The protocol was examined on five genes of interest, and for each, at least 50% knock-down in expression was achieved. While knock-down levels did not reach 100% in any trial, a well-controlled experiment with one heat-shock gene showed unambiguously that such partial gene suppression may cause dramatic changes in phenotype. Copepods with suppressed expression of heat-shock protein beta 1 (hspb1) exhibited dramatically decreased tolerance to high temperatures, validating the importance of this gene during thermal stress, as proposed by a previous study. The application of this RNAi protocol in T. californicus will be invaluable for examining the role of genes putatively involved in reproductive isolation, mitochondrial function and local adaptation.
Data from: Independent reversals to terrestriality in squirrels (Rodentia: Sciuridae) support ecologically mediated modes of adaptation
The family Sciuridae is one of the most widespread and ecologically diverse lineage of rodents and represents an ideal model for investigating the evolution of locomotion modes and the historical biogeography of terrestrial mammals. We used a comprehensive database on locomotion modes, an updated phylogeny and novel biogeographic comparative methods to re-assess the evolution of locomotion of squirrels and to investigate if these locomotion modes evolved convergently in different continents. We found that locomotion changes occurred in different independent lineages of the family, including four reversals to terrestriality and one evolution of gliding. We also found evidence for Eurasia as the center of origin of Sciuridae, challenging the classification of the oldest squirrel fossil records from the early Oligocene in North America. Additionally, Eurasia is also the possible center of origin for most of squirrel sub-families and tribes, and where locomotion changes have occurred. Parallel locomotion shifts could be explained by the adaptation towards different ecological niches followed by colonization of new continents.
Data from: The contributions of premating and postmating selection episodes to total selection in sex-role-reversed Gulf pipefish
Empirical studies of sexual selection often focus on events occurring either before or after mating but rarely both and consequently may fail to discern the relative magnitudes and interactions of premating and postmating episodes of selection. Here, we simultaneously quantify premating and postmating selection in the sex-role-reversed Gulf pipefish by using a microsatellite-based analysis of parentage in experimental populations. Female pipefish exhibited an opportunity for selection (I) of 1.64, which was higher than that of males (0.35). Decompositions of I and the selection differential on body size showed that over 95% of the selection on females arose from the premating phase. We also found evidence for a trade-off between selection phases, where multiply mating females had significantly lower offspring survivorship compared to singly mated females. In males, variance in relative fitness arose mainly from the number of eggs received per copulation and a small number of males who failed to mate. Overall, our study exemplifies a general approach for the decomposition of total selection into premating and postmating phases to understand the interplay among components of natural and sexual selection that conspire to shape sexually selected traits.
Seasonal survival and reversible state effects in a long-distance migratory shorebird
<p>1. Events during one stage of the annual cycle can reversibly affect an individual's condition and performance not only within that stage, but also in subsequent stages (i.e., reversible state effects). Despite strong conceptual links, however, few studies have been able to empirically link individual-level reversible state effects with larger-scale demographic processes.</p> <p>2. We studied both survival and potential reversible state effects in a long-distance migratory shorebird, the Hudsonian Godwit (Limosa haemastica). Specifically, we estimated period-specific survival probabilities across the annual cycle and examined the extent to which an individual's body condition, foraging success, and habitat quality during the nonbreeding season affected its subsequent survival and reproductive performance.</p> <p>3. Godwit survival rates were high throughout the annual cycle, but lowest during the breeding season, only slightly higher during southbound migration, and highest during the stationary nonbreeding season. Our results indicate that overwintering godwits foraging in high-quality habitats had comparably better nutritional status and pre-migratory body condition, which in turn improved their return rates and the likelihood that their nests and chicks survived during the subsequent breeding season.</p> <p>4. Reversible state effects thus appeared to link events between nonbreeding and breeding seasons via an individual's condition, in turn affecting their survival and subsequent reproductive performance. Our study thus provides one of the few empirical demonstrations of theoretical predictions that reversible state effects have the potential to influence population dynamics. </p>
Climate change, sex reversal, and lability of sex determining systems
Sex reversal at high temperatures during embryonic development (e.g. ZZ females) provides the opportunity for new genotypic crosses (e.g. ZZ male x ZZ female). This raises the alarming possibility that climatic warming could lead to the loss of an entire chromosome – one member of the sex chromosome pair (the Y or W) – and the transition of populations to environmental sex determination (ESD). Here we examine the evolutionary dynamics of sex-determining systems exposed to climatic warming using theoretical models. We found that the loss of sex chromosomes is not an inevitable consequence of sex reversal. A large frequency of ZZ sex reversal (50% reversal from male to female) typically divides the outcome between loss of the ZW genotype and the stable persistence of ZZ males, ZW females, and ZZ females. The amount of warming associated with sex chromosome loss depended on several features of wild populations – environmental fluctuation, immigration, heritable variation in temperature sensitivity, and differential fecundity of sex-reversed individuals. Chromosome loss was partially or completely buffered when sex-reversed individuals suffered a reproductive fitness cost, when immigration occurred, or when heritable variation for temperature sensitivity existed. Thus, under certain circumstances, sex chromosomes may persist cryptically in systems where the environment is the predominant influence on sex.
Data from: Reversal of response to artificial selection on body size in a wild passerine
A general assumption in quantitative genetics is the existence of an intermediate phenotype with higher mean individual fitness in the average environment than more extreme phenotypes. Here we investigate the evolvability and presence of such a phenotype in wild bird populations from an eleven-year experiment with four years of artificial selection for long and short tarsus length, a proxy for body size. The experiment resulted in strong selection in the imposed directions. However, artificial selection was counteracted by reduced production of recruits in offspring of artificially selected parents. This resulted in weak natural selection against extreme trait values. Significant responses to artificial selection were observed at both the phenotypic and genetic level, followed by a significant return towards pre-experimental means. During artificial selection, the annual observed phenotypic response closely followed the predicted response from quantitative genetic theory (ryear = 0.96, rcohorts = 0.56). The rapid return to pre-experimental means was induced by three interacting mechanisms: selection for an intermediate phenotype, immigration and recombination between selected and unselected individuals. The results of this study demonstrates the evolvability of phenotypes and that selection may favour an intermediate phenotype in wild populations.
Data from: The cost of being big: local competition, importance of dispersal and experimental evolution of reversal to unicellularity
Multicellularity provides multiple benefits. Nonetheless, unicellularity is ubiquitous and there have been multiple cases of evolutionary reversal to a unicellular organization. In this paper, we explore some of the costs of multicellularity as well as the possibility and dynamics of evolutionary reversals to unicellularity. We hypothesize that recently evolved multicellular organisms would face a high cost of increased competition for local resources in spatially structured environments because of larger size and increased cell densities. To test this hypothesis we conducted competition assays, computer simulations, and selection experiments using isolates of Saccharomyces cerevisiae that recently evolved multicellularity. In well-mixed environments, multicellular isolates had lower growth rates relative to their unicellular ancestor due to limitations of space and resource acquisition. In structured environments with localized resources, cells in both multicellular and unicellular isolates grew at a similar rate. Despite similar growth, higher local density of cells in multicellular groups led to increased competition and higher fitness costs in spatially structured environments. In structured environments all of the multicellular isolates rapidly evolved a predominantly unicellular life cycle, while in well-mixed environments reversal was more gradual. Taken together, these results suggest that a lack of dispersal, leading to higher local competition, might have been one of the main constraints in the evolution of early multicellular forms.
Data from: Novel reverse radioisotope labelling experiment reveals carbon assimilation of marine calcifiers under ocean acidification conditions
<p><span>1. Ocean acidification by anthropogenic carbon dioxide emissions is projected to depress metabolic and physiological activity in marine calcifiers. To evaluate the sensitivity of marine organisms against ocean acidification, the assimilation of nutrients into carbonate shells and soft tissues must be examined.</span></p> <p><span>2. We designed a novel experimental protocol, reverse radioisotope labelling, to trace partitioning of nutrients within a single bivalve species under ocean acidification conditions. Injecting CO<sub>2</sub> gas, free from radiocarbon, can provide a large contrast between carbon dissolved in the water and the one assimilated from atmosphere. By culturing modern aquifer organisms in acidified seawater, we were able to determine differences in the relative contributions of the end members, dissolved inorganic carbon (DIC) in seawater and metabolic CO<sub>2</sub>, to shell carbonate and soft tissues. </span></p> <p><span>3. Under all pCO<sub>2</sub> conditions (463, 653, 872, 1137, and 1337 μatm), radiocarbon (Δ<sup>14</sup>C) values of the bivalve (<i>Scapharca broughtonii</i>) shell were significantly correlated with seawater DIC values; therefore, shell carbonate was derived principally from seawater DIC. The Δ<sup>14</sup>C results together with stable carbon isotope (δ<sup>13</sup>C) data suggest that in <i>S. broughtonii</i> shell δ<sup>13</sup>C may reflect the kinetics of isotopic equilibration as well as end-member contributions; thus, care must be taken when analyzing end-member contributions by a previous method using δ<sup>13</sup>C. The insensitivity of <i>S. broughtonii</i> to perturbations in pCO<sub>2</sub> up to at least 1337 µatm indicates that this species can withstand ocean acidification.</span></p> <p><span>4. Usage of radioisotope to dope for tracer experiments requires strict rules to conduct any operations. Yet, reverse radioisotope labeling proposing in this study has a large advantage and is a powerful tool to understanding physiology of aquifer organisms that can be applicable to various organisms and culture experiments, such as temperature, salinity, and acidification experiments, to improve understanding of the proportions of nutrients taken in by marine organisms under changing environments.</span></p>
Data from: An invasive species reverses the roles in a host-parasite relationship between bitterling fish and unionid mussels
The impact of multiple invading species can be magnified due to mutual facilitation, termed "invasional meltdown", but invasive species can also be adversely affected by their interactions with other invaders. Using a unique reciprocal host-parasite relationship between a bitterling fish, Rhodeus amarus, and unionid mussels, we show that an invasive mussel reverses the roles in the relationship. Bitterling lay their eggs into mussel gills, and mussel larvae parasitize fish. Bitterling recently colonized Europe and parasitize all sympatric European mussels, but are unable to utilize a recently invasive mussel, Anodonta woodiana. The parasitic larvae of A. woodiana successfully develop on R. amarus, while larvae of European mussels are rejected by bitterling. This demonstrates that invading species may temporarily benefit from a coevolutionary lag by exploiting evolutionarily naïve hosts, but the resulting relaxed selection may facilitate its exploitation by subsequent invading species, leading to unexpected consequences for established interspecific relationships.
FIGURE 10 in Re-description of Orchestia stephenseni Cecchini, 1928: designation of neotype and senior synonym to Orchestia constricta A. Costa, 1853 (Crustacea: Amphipoda: Talitridae) by Reversal of Precedence
FIGURE 10. Iconography of Orchestia mediterranea A. Costa, male, by Bulycheva (1957); PpV, peraeopod 7.
FIGURE 8. Orchestia stephenseni Cecchini, 1928 in Re-description of Orchestia stephenseni Cecchini, 1928: designation of neotype and senior synonym to Orchestia constricta A. Costa, 1853 (Crustacea: Amphipoda: Talitridae) by Reversal of Precedence
FIGURE 8. Orchestia stephenseni Cecchini, 1928. Male. Details of shapes of palm and dactylus of gnathopod 2, dactylus of peraeopod 3 and peraeopod 4, merus, carpus and propodus of gnathopod 1 and palp of maxilliped.
FIGURE 6 in Re-description of Orchestia stephenseni Cecchini, 1928: designation of neotype and senior synonym to Orchestia constricta A. Costa, 1853 (Crustacea: Amphipoda: Talitridae) by Reversal of Precedence
FIGURE 6. NJ tree constructed on the K2P model performed with 630-bp COI sequences, including sequences of the five O. stephenseni shapes, the Sicilian O. montagui and O. mediterranea samples, and sequences reference (*) from GenBank (shown with the A.N.). The values allocated to the nodes were those calculated on 1,000 bootstrap replicates.
FIGURE 7 in Re-description of Orchestia stephenseni Cecchini, 1928: designation of neotype and senior synonym to Orchestia constricta A. Costa, 1853 (Crustacea: Amphipoda: Talitridae) by Reversal of Precedence
FIGURE 7. Iconography of Orchestia stephenseni Cecchini, 1928. Male. Morphotype V. Gnathopods 2 of specimens ascribed to Morphotype I–IV are shown. Peraeopod 7 of specimens ascribed to Morphotype I is shown. See text for terminology. Scale bar = 1 mm.
FIGURE 2. The five O. stephenseni morphotypes, named Morphotype I in Re-description of Orchestia stephenseni Cecchini, 1928: designation of neotype and senior synonym to Orchestia constricta A. Costa, 1853 (Crustacea: Amphipoda: Talitridae) by Reversal of Precedence
FIGURE 2. The five O. stephenseni morphotypes, named Morphotype I to V, and corresponding to the five gnathopod 2 shapes. The body-length for each photographed individual is reported. Scale bar = 1 mm.
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Allen Brain Atlas
Allen Brain Atlas is an Allen Institute collection of brain map atlases, datasets, APIs, and analysis tools covering mouse, human, and non-human primate brain resources.
Annotated Behaviour and Observability Dataset (ABODe)
ABODe is a University of Edinburgh DataShare dataset for behavior classification in group-housed mice using home-cage video, identities, bounding boxes, ground-plate positions, and annotator labels.
DANDI Archive for NWB datasets
DANDI is a BRAIN Initiative archive for publishing and sharing neurophysiology data, including electrophysiology, optophysiology, and behavioral data packaged as NWB and related standards.
International Brain Laboratory public data
The International Brain Laboratory public data releases expose standardized mouse decision-making experiments, including Neuropixels recordings, widefield calcium imaging, behavior, and session metadata accessed through the ONE API.
OpenNeuro
OpenNeuro is a free, open platform for sharing neuroimaging datasets, with public search, dataset pages, and download paths for web, S3, DataLad, and the OpenNeuro CLI.