Linear confinement and stress-energy tensor around static quark and anti-quark pair -- Lattice simulation with Yang-Mills gradient flow --

We study the spatial distribution of the stress tensor around static quark-anti-quark pair in SU(3) lattice gauge theory. In particular, we reveal the transverse structure of the stress tensor distribution in detail by taking the continuum limit. The Yang-Mills gradient flow plays a crucial role to make the stress tensor well-defined and derivable from the numerical simulations on the lattice.Comment: 7 pages, 4 figures, Fig.3 is corrected, Proceedings for the 36th Annual International Symposium on Lattice Field Theory (Lattice 2018

The eco‐evolutionary dynamics of prior selfing rates promote coexistence without niche partitioning under conditions of reproductive interference

1. Pollinator-mediated reproductive interference can occur when two or more plant species share the same pollinators. Recent studies have suggested that prior autonomous selfing mitigates reproductive interference, potentially facilitating coexistence even in the absence of pollination niche partitioning (i.e. the pre-emptive selfing hypothesis). However, whether the evolution of prior selfing promotes coexistence, in the context of the eco-evolutionary dynamics of population size, selfing rates and inbreeding depression, remains poorly understood. 2. We constructed an individual-based model to examine the conditions under which the evolution of prior selfing promotes coexistence in the context of mutual reproductive interference. In the model, two plant species compete by way of mutual reproductive interference, and both have the potential to evolve the capacity for prior autonomous selfing. We expected that purging of deleterious mutations might result in evolutionary rescue, assuming that the strength of inbreeding depression declines as the population selfing rate increases; this would enable inferior competitors to maintain population density through the evolution of prior selfing. 3. Our simulation demonstrated that evolution of prior selfing may promote coexistence, whereas reproductive interference in the absence of such evolution results in competitive exclusion. We found that lower pollinator availability is likely to favour rapid evolutionary shifts to higher prior selfing rates, thereby neutralising the negative effects of reproductive interference in both species. When the strength of inbreeding depression decreased with an increase in the population-level selfing rate, moderate pollinator availability resulted in long-term coexistence in which relative abundance-dependent selection on the prior selfing rate served to intermittently maintain the population density of the inferior competitor. 4. Synthesis. We demonstrate that the evolution of prior selfing may increase population growth rates of inferior competitors and may consequently promote long-term coexistence via an evolutionary rescue. This constitutes a novel mechanism explaining the co-evolutionary coexistence of closely related plant species without niche partitioning, and is consistent with recent studies reporting that closely related species with mixed mating systems can co-occur sympatrically, even under conditions of mutual reproductive interference

Distribution of Stress Tensor around Static Quark--Anti-Quark from Yang-Mills Gradient Flow

The spatial distribution of the stress tensor around the quark--anti-quark ($Q\bar{Q}$) pair in SU(3) lattice gauge theory is studied. The Yang-Mills gradient flow plays a crucial role to make the stress tensor well-defined and derivable from the numerical simulations on the lattice. The resultant stress tensor with a decomposition into local principal axes shows, for the first time, the detailed structure of the flux tube along the longitudinal and transverse directions in a gauge invariant manner. The linear confining behavior of the $Q\bar{Q}$ potential at long distances is derived directly from the integral of the local stress tensor.Comment: 7 pages, 4 figures, Fig.3 is corrected, version published in Phys. Lett.

Understanding the role of eco-evolutionary feedbacks in host-parasite coevolution

It is widely recognised that eco-evolutionary feedbacks can have important implications for evolution. However, many models of host-parasite coevolution omit eco-evolutionary feedbacks for the sake of simplicity, typically by assuming the population sizes of both species are constant. It is often difficult to determine whether the results of these models are qualitatively robust if eco-evolutionary feedbacks are included. Here, by allowing interspecific encounter probabilities to depend on population densities without otherwise varying the structure of the models, we provide a simple method that can test whether eco-evolutionary feedbacks per se affect evolutionary outcomes. Applying this approach to explicit genetic and quantitative trait models from the literature, our framework shows that qualitative changes to the outcome can be directly attributable to eco-evolutionary feedbacks. For example, shifting the dynamics between stable monomorphism or polymorphism and cycling, as well as changing the nature of the cycles. Our approach, which can be readily applied to many different models of host-parasite coevolution, offers a straightforward method for testing whether eco-evolutionary feedbacks qualitatively change coevolutionary outcomes

Data from: Joint evolution of differential seed dispersal and self-fertilization

Differential seed dispersal, in which selfed and outcrossed seeds possess different dispersal propensities, represents a potentially important individual-level association. A variety of traits can mediate differential seed dispersal, including inflorescence and seed size variation. However, how natural selection shapes such associations is poorly known. Here, we developed theoretical models for the evolution of mating system and differential seed dispersal in metapopulations, incorporating heterogeneous pollination, dispersal cost, cost of outcrossing, and environment-dependent inbreeding depression. We considered three models. In the “fixed dispersal model,” only selfing rate is allowed to evolve. In the “fixed selfing model,” in which selfing is fixed but differential seed dispersal can evolve, we showed that natural selection favours a higher, equal, or lower dispersal rate for selfed seeds to that for outcrossed seeds. However, in the “joint evolution model,” in which selfing and dispersal can evolve together, evolution necessarily leads to higher or equal dispersal rate for selfed seeds compared to that for outcrossed. Further comparison revealed that outcrossed seed dispersal is selected against by the evolution of mixed mating or selfing, whereas the evolution of selfed seed dispersal undergoes independent processes. We discuss the adaptive significance and constraints for mating system/dispersal association

The evolution of stage‐specific virulence: Differential selection of parasites in juveniles

Abstract The impact of infectious disease is often very different in juveniles and adults, but theory has focused on the drivers of stage‐dependent defense in hosts rather than the potential for stage‐dependent virulence evolution in parasites. Stage structure has the potential to be important to the evolution of pathogens because it exposes parasites to heterogeneous environments in terms of both host characteristics and transmission pathways. We develop a stage‐structured (juvenile–adult) epidemiological model and examine the evolutionary outcomes of stage‐specific virulence under the classic assumption of a transmission‐virulence trade‐off. We show that selection on virulence against adults remains consistent with the classic theory. However, the evolution of juvenile virulence is sensitive to both demography and transmission pathway with higher virulence against juveniles being favored either when the transmission pathway is assortative (juveniles preferentially interact together) and the juvenile stage is long, or in contrast when the transmission pathway is disassortative and the juvenile stage is short. These results highlight the potentially profound effects of host stage structure on determining parasite virulence in nature. This new perspective may have broad implications for both understanding and managing disease severity