In this graphical abstract, a flow chart on the left outlines the criteria used to classify novel environments. On the right, two forest plots are presented: one comparing effect sizes (standardized mean difference in total genetic variance, SDV) between extreme and absolute novel environments, and the other comparing effect sizes between broad-sense and narrow-sense study designs.

Code review is the process of either informally (as part of a group, as colleagues) or formally (as part of the peer review process) checking and evaluating each other's code and is a critical method of reducing errors and increasing research reproducibility and reliability. In this paper, we provide a detailed commentary on how to effectively review code (including introducing the four Rs), how to set up your project to enable this form of review and detail its possibleimplementation at several stages throughout the research process.

We study the process of local adaptation in the common chaffinch to two contrasting habitats on the island of La Palma, the humid laurel forest and the dry pine forest. We document habitat-related phenotypic divergence, and using genome–environment association analysis on a small fraction of the genome, we detect adaptive genomic divergence at a small spatial scale associated with habitat type.

Comparing brain morphology across a Panamanian community of Heliconius butterflies, we find evidence for interspecific variation along two axes: heritable divergence in the size of visual brain components, and plastic differences in mushroom body size, a central component of learning and memory systems. We illustrate the impact of small-scale spatial effects on mushroom body plasticity.

Populations may make bad predictions when when using partially reliable cues to track changing environments (left). These mistakes can render plasticity deleterious (s < 0); right) when cue reliability is low, but dispersal among demes spreads out the effects of mistakes and allows the evolution of adaptive plasticity.

Fast development in Drosophila leads to increased basal immune function.

Why warning patterns are so diverse is an enduring evolutionary puzzle. Because predators associate particular patterns with unpleasant experiences, an individual’s predation risk should decrease as the local density of its warning pattern increases, promoting pattern monomorphism. Male Heliconius use warning patterns as mating cues, but mated females may suffer costs if this leads to disturbance, favouring novel patterns.

Haldane's rule: when hybrids from one sex are absent, rare or sterile, that sex is always the heterogametic sex.

We present Bait-ER - a method for estimating selection in allele frequency trajectory data from E&R experiments. Bait-ER models allele frequencies through time in a population with overlapping generations. Our method performs well in both simulated and real time series data and it tests for selection without the need for simulating an empirical null distribution.

We quantified the extent of phenotypic parallelism among high and low-predation ecotype pairs using data from published studies on Trinidadian guppies, long considered a classic study system in parallel evolution. We did so overall, and in regard to six factors that might contribute to the extent of parallelism: sex, trait type, rearing environment, ecological complexity, evolutionary history, and time since colonization. R² values indicate amount of parallelism, and we found that colour traits are especially weakly parallel and that evolutionary history is an important contributor to the extent of parallelism. Our results contribute to the growing consensus that the extent of parallelism in fish is variable and often weak.

Yellow and red autumn leaves typical to temperate/boreal trees defend important resources released following the photosynthetic system breakdown, and mobilized for storage to be used in the next spring. This coloration, especially red, defends from excess light and oxidative stress and against herbivores. I describe the hypotheses, findings and disagreements about the functions and evolution of yellow/red autumn leaves.

By evaluating horned dung beetles in contaminated cattle pastures, our study reveals that contamination interferes with sexual selection by affecting male's relative investment to sexual traits. Higher abundance of large-horned males in contaminated pastures indicates demographic impacts of sexual selection in nature and can be explained by evolutionary rescue promoted by sexual selection or by plastic responses in horn size according to population density. The orange arrows support the results of this work.

Inference in ecology and evolution is still mostly based on significance testing. We summarize problems with this approach and argue that it should be replaced by the adequate description of effect size estimates.

Recent theory suggests species’ range limits may be caused by edge populations suffering from mutation accumulation as a result of increased genetic drift. Here we tested whether the expression of mutational load of range-edge populations was dependent on environmental stress typical for peripheral environments. We found that the expression of mutational load was not enhanced under stress in Arabidopsis lyrata, but that this species suffers from a general stress-dependent heterozygote deficit. Our results suggest that range-edge populations may suffer from two independent genetic Allee effects, heightened mutational load and stress-dependent load linked to heterozygote deficiency.

Across parrot species, body size correlates with longer calls, lower sound frequency and wider frequency bandwidths, while sexual dichromatiam correlates negatively with various aspects of call complexity, as predicted by the transference hypothesis for the evolution of different sexual signals. Photos credits: © Wikimedia common.

Host-parasite coevolution is a reciprocal process of adaptations and counter-adaptations. When a parasite evolves to have heightened infectivity, its host may respond by evolving to have heightened resistance.

Reproductive interference (RI), costly reproductive interactions between individuals of different species, is a common yet little understood behaviour. In this study, we compare inter- and intraspecific mating dynamics in the squash bug Anasa tristis to better understand drivers of interspecific mating interactions. We uncovered high levels of reproductive interference (19% of individuals engaged in interspecific matings), but the majority of mating activity took place between conspecifics. Female Anasa tristis were also highly polyandrous, and we found those which engaged in occasional interspecific matings had comparable hatching success to those which did not. In this system, at least, relatively high levels of reproductive interference likely emerged as a by-product of relaxed intraspecific pre-copulatory choice, paired with limited fitness penalties in our focal species.

Epistatic interactions between sex chromosomes and autosomes can cause increased stability of the sex determination system, favouring its maintenance over the invasion of novel systems, or decreased stability where an invasion of a novel sex determination system becomes favoured. The nature of these effects on the stability of sex determination system depends strongly on the type of epistatic interaction, its strength, and the type of newly-invading sex determination gene.

Colour variation is common in camouflaged species. Variation may be continuous or discrete, with different patterns found in the same, or geographically distinct, populations. Sometimes variation is linked to microhabitat specialization, sometimes to the advantages of having a rare pattern (with which predators aren't familiar). In a Neotropical toad, we found that continuous colour pattern variation matches the local leaf-litter, such that the toads benefit from both microhabitat-specific camouflage and mimicking dead leaves.

Although numbers of studies have showed that sperm competition risks affect male’s ejaculate traits, the effect on sperm size evolution is still controversial. By comparison of two squid species, we show that while levels of sperm competition determine number of released sperm, sperm size are determined more by the mode of sperm storage and fertilization.