Reproductive isolation via polygenic local adaptation in sub-divided populations: effect of linkage disequilibria and drift

This paper considers how local adaptation and reproductive isolation between hybridizing populations is influenced by linkage disequilibria (LD) between multiple divergently selected loci in scenarios where both gene flow and genetic drift degrade local adaptation. It shows that the combined effects of multi-locus LD and genetic drift on allele frequencies at selected loci and on heterozygosity at neutral loci are predicted accurately by incorporating (deterministic) effective migration rates into the diffusion approximation (for selected loci) and into the structured coalescent (for neutral loci). Theoretical approximations are tested against individual-based simulations and used to investigate the conditions for the maintenance of local adaptation on an island subject to one-way migration from a differently adapted mainland, and in an infinite-island population with two different habitats under divergent selection. The analysis clarifies the conditions under which LD between sets of locally deleterious alleles allows these to be collectively eliminated despite drift, causing sharper and (under certain conditions) shifted migration thresholds for loss of adaptation. Local adaptation also has counter-intuitive effects on neutral (relative) divergence: FST is highest for a pair of subpopulations belonging to the same (rare) habitat, despite the lack of reproductive isolation between them.

Holographic Rényi relative divergence in JT gravity

We holographically compute the Rényi relative divergence Dα(ρ+||ρ−) between two density matrices ρ+, ρ− prepared by path integrals with constant background fields λ± coupled to a marginal operator in JT gravity. Our calculation is non-perturbative in the difference between two sources λ+− λ−. When this difference is large, the bulk geometry becomes a black hole with the maximal temperature allowed by the Rényi index α. In this limit, we find an analytical expression of the Rényi relative divergence, which is given by the on shell action of the back reacted black hole plus the contribution coming from the discontinuous change of the background field.

On the symmetrized s-divergence

In this study, we work with the relative divergence of type s,s\in {\mathbb{R}} , which includes the Kullback-Leibler divergence and the Hellinger and χ 2 distances as particular cases. We study the symmetrized divergences in additive and multiplicative forms. Some basic properties such as symmetry, monotonicity and log-convexity are established. An important result from the convexity theory is also proved.

Performance of A Priori and A Posteriori Calibration Strategies in Divergence Time Estimation

Relaxed molecular clock methods allow the use of genomic data to estimate divergence times across the tree of life. This is most commonly achieved in Bayesian analyses where the molecular clock is calibrated a priori through the integration of fossil information. Alternatively, fossil calibrations can be used a posteriori, to transform previously estimated relative divergence times that were inferred without considering fossil information, into absolute divergence times. However, as branch length is the product of the rate of evolution and the duration in time of the considered branch, the extent to which a posteriori calibrated, relative divergence time methods can disambiguate time and rate, is unclear. Here, we use forward evolutionary simulations and compare a priori and a posteriori calibration strategies using different molecular clock methods and models. Specifically, we compare three Bayesian methods, the strict clock, uncorrelated clock and autocorrelated clock, and the non-Bayesian algorithm implemented in RelTime. We simulate phylogenies with multiple, independent substitution rate changes and show that correct timescales cannot be inferred without the use of calibrations. Under our simulation conditions, a posteriori calibration strategies almost invariably inferred incorrect rate changes and divergence times. The a priori integration of fossil calibrations is fundamental in these cases to improve the accuracy of the estimated divergence times. Relative divergence times and absolute timescales derived by calibrating relative timescales to geological time a posteriori appear to be less reliable than a priori calibrated, timescales.

On the symmetrized S-divergence

In this paper we worked with the relative divergence of type s, s ∈ ℝ, which include Kullback-Leibler divergence and the Hellinger and χ2 distances as particular cases. We give here a study of the sym- metrized divergences in additive and multiplicative forms. Some ba-sic properties as symmetry, monotonicity and log-convexity are estab-lished. An important result from the Convexity Theory is also proved.

Believing in one's power: a counterfactual heuristic for goal-directed control

Most people envision themselves as operant agents endowed with the capacity to bring about changes in the outside world. This ability to monitor one's own causal power has long been suggested to rest upon a specific model of causal inference, i.e., a model of how our actions causally relate to their consequences. What this model is and how it may explain departures from optimal inference, e.g., illusory control and self-attribution biases, are still conjecture. To address this question, we designed a series of novel experiments requiring participants to continuously monitor their causal influence over the task environment by discriminating changes that were caused by their own actions from changes that were not. Comparing different models of choice, we found that participants' behaviour was best explained by a model deriving the consequences of the forgone action from the current action that was taken and assuming relative divergence between both. Importantly, this model agrees with the intuitive way of construing causal power as "difference-making" in which causally efficacious actions are actions that make a difference to the world. We suggest that our model outperformed all competitors because it closely mirrors people's belief in their causal power - a belief that is well-suited to learning action-outcome associations in controllable environments. We speculate that this belief may be part of the reason why reflecting upon one's own causal power fundamentally differs from reasoning about external causes.

Selection and gene flow shape genomic islands that control floral guides

Genomes of closely-related species or populations often display localized regions of enhanced relative sequence divergence, termed genomic islands. It has been proposed that these islands arise through selective sweeps and/or barriers to gene flow. Here, we genetically dissect a genomic island that controls flower color pattern differences between two subspecies of Antirrhinum majus, A.m.striatum and A.m.pseudomajus, and relate it to clinal variation across a natural hybrid zone. We show that selective sweeps likely raised relative divergence at two tightly-linked MYB-like transcription factors, leading to distinct flower patterns in the two subspecies. The two patterns provide alternate floral guides and create a strong barrier to gene flow where populations come into contact. This barrier affects the selected flower color genes and tightly-linked loci, but does not extend outside of this domain, allowing gene flow to lower relative divergence for the rest of the chromosome. Thus, both selective sweeps and barriers to gene flow play a role in shaping genomic islands: sweeps cause elevation in relative divergence, while heterogeneous gene flow flattens the surrounding “sea,” making the island of divergence stand out. By showing how selective sweeps establish alternative adaptive phenotypes that lead to barriers to gene flow, our study sheds light on possible mechanisms leading to reproductive isolation and speciation.

Systematics of the Culex coronator complex (Diptera: Culicidae): morphological and molecular assessment

The Culex coronator complex of the mosquito subgenus Culex includes five currently recognized species: Cx. camposi, Cx. coronator, Cx. ousqua, Cx. usquatissimus and Cx. usquatus. Because of the confusing taxonomic history of the complex, we aimed to clarify the specific status of these nominal forms based on an examination of holotypes and lectotypes and molecular data from other specimens. Critical assessment of published descriptions and study of type specimens revealed that the known distributions of the five species overlap considerably and exhibit biotic sympatry in some areas. Sequences from the COI barcode region and complete mitochondrial genomes were used to assess the relationships and degree of genetic divergence of the species and two newly discovered morphological forms, Cx. coronator Forms 1 and 2. Genetic distances in the COI dataset varied from 0.00 to 2.67%, with the largest relative divergence being 4.41 between specimens of Cx. coronator and Cx. coronator Form 1. Bayesian Poisson tree process analysis of the COI barcode region also failed to provide support for the nominal species. Evidence from the morphological and molecular data thus leads us to conclude (at least provisionally) that the Cx. coronator complex is a single polymorphic species. The forms constitute a monophyletic group but there is no support for the specific status of the five nominal forms.