Journal of Evolutionary Biology最新文献

Sexual selection is responsible for the evolution of exaggerated morphologies in males of many animal species. In extreme cases, this has led to the emergence of novel morphs, which differ discretely from ancestral phenotypes. Morphological studies of sexually selected traits in males have mainly focused on species in which trait expression is continuous. How trait expression varies in species with discrete male morphs is comparably understudied. We find that wingless and winged male morphs in the ant Cardiocondyla obscurior differ in size and variation of eight morphological traits, including mandibles used as weapons in fights between wingless males. Differences between morphs were consistent across populations, but the size of some traits varied by population origin, even though all animals were lab-reared under identical conditions. In contrast to weapons in males of many other species, the mandibles of wingless males showed negative allometry with body size. Mandibles exhibited similar levels of fluctuating asymmetry in both morphs; in wingless males, mandible asymmetry was negatively correlated with mandible length, suggesting that stable mandible development may be an indicator of overall quality of fighter males. Mandible length showed less variation in wingless males than in winged males, whereas all other traits were more variable in wingless males, including highly conserved traits, such as antenna segment number. Wingless males also exhibited more variation in trait size than female queens and workers. Together, these data point towards stabilizing selection on weapon phenotype but overall low levels of developmental stability and canalization in an evolutionarily novel ant morph.

Phylogenetic comparative methods (PCMs) are fundamental tools for understanding trait evolution across species. While linear models are widely used for continuous traits in ecology and evolution, their application to discrete traits, particularly ordinal and nominal traits, remains limited. Researchers sometimes recategorise such traits into binary traits (0 or 1 data) to make them more manageable. However, this risks distorting the original data structure and meaning, potentially reducing the information it initially contained. This paper promotes the use of phylogenetic generalised linear mixed-effects models (PGLMMs) as a flexible framework for analysing the evolution of discrete traits. We introduce the theoretical foundations of PGLMMs and demonstrate how univariate and multivariate versions of binary PGLMMs, which might be more familiar to evolutionary biologists, can be conceptually extended to model ordinal and nominal traits. Specifically, we describe ordered and unordered multinomial PGLMMs for ordinal and nominal traits, respectively. We then explain how to interpret regression coefficients and (co)variance components, including associated statistics (e.g., phylogenetic heritability and correlation) from PGLMMs for discrete traits. Using real-world examples from avian datasets, we illustrate the practical implementation of PGLMMs to reveal evolutionary patterns in discrete traits. We also provide online tutorials to guide researchers through the application of these models using Bayesian implementations in R. By making complex models more accessible, we aim to facilitate a more precise and insightful understanding of the evolution and function of discrete traits, which have received relatively limited attention in evolutionary biology so far.

Competitive intransitivity, or non-hierarchical interactions, such as those exemplified by the rock-paper-scissors game where no single competitor wins outright, has been proposed as a key mechanism for maintaining biodiversity; however, empirical evidence supporting the importance of intransitivity remains limited. Natural populations of Saccharomyces cerevisiae often include strains harboring totivirus-satellite coinfections that encode a lethal toxic glycoprotein capable of eliminating competing yeast strains. Killer strains are sparsely distributed in natural populations, despite their assumed competitive advantage. Yeast isolates occasionally exhibit toxin resistance, but it remains untested whether they can outcompete and replace killer strains. Similarly, the persistence of toxin-susceptible yeast is not well understood - particularly whether they can invade resistant populations in the absence of killers, thereby completing an intransitive loop. In a multi-year collection of yeast isolates from vineyards across New Zealand, we observed a near-complete disappearance of a previously common killer yeast genotype of S. cerevisiae over consecutive years. Using space-time-shift competition assays, we demonstrate that strains sympatric to this killer genotype were ubiquitously resistant, unlike the allopatric strains that were frequently eliminated in competition assays. Furthermore, the extinction of the focal killer genotype appears to have enabled the emergence of toxin-susceptible competitors in sites formerly occupied by the killer genotype. Our findings suggest that the competitive advantage of toxin production is evident in natural populations but appears to be eroded when resistance evolves in competitors of the focal killer genotype. We suggest that such killer-resistant-susceptible polymorphisms are being maintained by evolutionary dynamics akin to rock-paper-scissors-like intransitivity, driven by the invasion of susceptible strains after costly resistance has driven killer strains to extinction in natural populations, all being driven by toxin-encoding coinfections.

Uncovering the genetic basis of sexually selected traits and traits involved in sexual conflict is a key to understand the association between sexual and non-sexual fitness. 6-phosphogluconate dehydrogenase (6Pgdh) is a metabolic gene associated with pentose phosphate pathway. It was shown to be involved in sexual selection and conflict in bulb mite, Rhizoglyphus robini. Two previously identified 6Pgdh genotypes are associated with variation in male reproductive fitness: the "winning" 6Pgdh allele (S) confers advantage in male reproductive success compared to the alternative F allele, but mating with S-bearing males decreases female fecundity. Physiological mechanisms of these differences remain a puzzle. We compare gene expression patterns between males from the S- and F-allele homozygous lines to identify which molecular pathways are affected by 6Pgdh polymorphism. Moreover, we test for linkage disequilibrium in gene-coding regions associated with genetic polymorphism in 6Pgdh and show that polymorphism in 6Pgdh is in linkage disequilibrium with nonsynonymous single nucleotide polymorphisms in five genes, four of which are located within the same chromosome. We show that male genotype in 6Pgdh is associated with differential expression of genes distributed throughout the whole genome. Among differentially expressed genes, we found overrepresentation of several categories associated with fructose metabolism, including an enzyme associated with both pentose phosphate metabolism and glycolysis. Differential expression in genes associated with a number of other general categories highlight the connection between sexual fitness and gene expression in a number of important pathways, potentially affecting performance of a whole organism.

Mitochondrial function relies on close coordination between the mitochondrial and nuclear genomes. Disruption to this coordination-via mitonuclear mismatch-can impair metabolic efficiency, particularly under energetically demanding conditions such as during development. The nutritional environment further modulates mitochondrial demands, suggesting that mitonuclear genotype and diet may interact to shape life-history traits and behaviour. Here, we investigate how early-life diet and mitonuclear genotype jointly influence development time, adult body size, and nutritional preference in Drosophila melanogaster. Using a full-factorial panel of putatively matched and mismatched combinations (cybrids) of mitonuclear genotype derived from natural Australian populations, we reared flies on diets varying in their ratio of macronutrients and assessed how this influenced larval development and subsequent adult diet preference. Developmental rate was significantly influenced by mitonuclear coevolution and diet, with cybrids showing delayed development under all conditions, with dietary extremes exacerbating this effect. Despite this, egg-to-adult viability remained unaffected. Adult nutritional behaviour exhibited clear genotype- and diet-dependent effects. Flies reared on high-protein diets increased carbohydrate intake as adults, while those reared on high-carbohydrate diets increased protein intake, suggesting compensatory feeding responses. Mitonuclear mismatch further modulated nutrient consumption, particularly in females, whose carbohydrate intake was influenced by intergenomic compatibility and early-life dietary conditions. Males' protein consumption was also impacted by mitonuclear coevolution across all developmental diets. Finally, body size was also shaped by interactions between mitonuclear genotype and diet. Together, our findings demonstrate that mitonuclear compatibility and the composition of the early nutritional environment interact to shape developmental and behavioural phenotypes. These results support a role for mitonuclear coadaptation in mediating metabolic plasticity, highlighting the evolutionary and physiological significance of genotype-specific mitonuclear coordination.

Maternal investment is hypothesized to have a direct influence on the size of energetically costly organs, including the brain. In placental organisms, offspring are supplied with nutrients during prenatal development, potentially modulating brain size. Previous research has predominantly focused on mammalian species that exhibit both pre- and postnatal provisioning, in which effects on brain size have been observed during both developmental stages. Here, using eight poeciliid fish species, we test if those species with placental structures (i.e., matrotrophy) invest more resources into offspring brain development than species without placental structures (i.e., lecithotrophy). The prediction is that matrotrophy may entail higher nutrient provisioning rates to the developing embryo, resulting in larger offspring brain sizes, compared to species with a lecithotrophic strategy. To test this prediction, we took non-invasive brain size measurements during the first four weeks of life, comparing these to somatic growth measurements. Contrary to our expectations, we did not find any differences in brain size between the two maternal strategies in poeciliids. Furthermore, we did not find any differences in how relative brain size changed over ontogenetic development, between placental and non-placental species. In contrast to the marsupial/placental transition, the fish species investigated here only exhibit prenatal provisioning, which may reduce the potential for maternal investment into brain size. Consequently, our results suggest that coevolution between placental structures and juvenile brain size is not a general pattern in vertebrates.

Post-ejaculatory sexual selection in the form of cryptic female choice provides opportunities for females to bias paternity to favor preferred males. However, little is known regarding how cryptic female choice might affect offspring outside of paternity, via female modified changes to environments that sperm experience prior to fertilization. Ejaculate-mediated paternal effects are widespread, and female alteration of sperm experience may play an unrecognized role in shaping cryptic female choice. Using hybridizing salmonid fishes that have documented female reproductive fluid mediated conspecific sperm precedence, we created artificial split-brood and split-ejaculate fertilizations to determine if sperm experience in different fluids influences offspring development. Prior to contact with eggs, sperm experienced 20s of swimming in either water, or water with the addition of conspecific female fluid or heterospecific female fluid. Over 186 days, we quantified hatch timing, hatchling size, and developmental stage and found that reproductive fluid from different species created biologically irrelevant (average effect size of 1.05%) changes on offspring development, which were much smaller than the effects of hybridization itself (average effect size of 10.44% for the species of the father). Since female reproductive fluid drastically changes fertilization conditions when compared to water, we conclude that females can use reproductive fluid to bias paternity without concomitant consequences to offspring development.

The additive genetic variance of a quantitative trait usually is interpreted as a measure of its evolvability, i.e., its capacity for adaptive evolution. However, in populations with overlapping generations, evolvability is also affected by the parental age at reproduction because genotypes that reproduce earlier evolve faster than genotypes with later reproduction. I show here that directional selection of a phenotypic trait inevitably links it with relative age at reproduction and thus developmental timing, whether or not age at reproduction affects reproductive success. In turn, the evolved genetic covariance between the selected trait and reproductive age accelerates the evolutionary response of the trait mean, unless counteracted by strong selection for late reproduction. Hence, not only the genetic variance of the trait but also the genetic variance in age at reproduction contributes to a trait's evolvability, even if the trait was initially unrelated to age at reproduction. I further show that stable generation time requires selection of intermediate strength for later reproduction and that episodes of strong selection tend to shorten average generation time. After a proof of principle by individual-based simulations, I present a formalization of this theory in a quantitative genetic framework, leading to a relatively simple extension of the breeder's equation. Finally, I discuss empirical evidence and implications for senescence and life history evolution.

D. bipectinata and D. malerkotliana are two closely related species that share common ecological niches throughout their distribution zone which comes under Oriental-Australian zoogeographical regions. These two species have been found to share several common genetic characteristics and due to this, they may experience interspecific mating under laboratory conditions and produce hybrid progeny. The population genetical work on these two species has been inadequately done by considering inversions and enzyme polymorphisms. We decided to consider the genetic polymorphism involving commonly persistent chromosomal inversions, allozymes and microsatellite variants of the two species to envisage genetic differentiation among the natural populations of these two species sampled from distant localities of Indian cities. The results of this study indicate that Indian populations of both the species are genetically structured. There exists graded variation (clinal variation) in the level of heterozygosity from north to south as an increase in the observed heterozygosity prevailed from north to south. This trend was observed in the populations of both the species that hints towards similar genetic changes being experienced by its members all along their distribution area. The phylogenetic trees based on the extent of genetic identity between the paired populations of these two species portray two distinct clusters, one for the two populations of north and the other for the remaining populations of south. Further, through this study, it can be stated with certainty that there exists "isolation by distance" as the north and south populations of both the species genetically significantly vary from each other.

Phenology and the timing of development are often under selection. However, the relative contributions of genotype, environment, and prior developmental transitions to variance in the phenology of wild plants is largely unknown. Individual components of phenology (e.g., germination) might be loosely related with the timing of maturation due to variation in prior developmental transitions. Given widespread evidence that genetic variation in life history is adaptive, we investigated to what degree experimentally measured genetic variation in Arabidopsis phenology predicts phenology of plants in the wild. As a proxy of phenology, we obtained collection dates from nature of 227 naturally inbred Arabidopsis thaliana accessions from across Eurasia. We compared this phenology in nature with experimental data on the descendant inbred lines that we synthesized from two new and 155 published controlled experiments. We tested whether the genetic variation in flowering and germination timing from experiments predicted the phenology of the same lines in nature. We found that genetic variation in phenology from controlled experiments significantly predicts day of collection from wild individuals, as a proxy for date of flowering, across Eurasia. However, local variation in collection dates within a region was not explained by genetic variance in phenology in experiments, suggesting high plasticity across small-scale environmental gradients or complex interactions between the timing of different developmental transitions. While experiments have shown phenology is under selection, understanding the subtle environmental and stochastic effects on phenology may help to clarify the heritability and evolution of phenological traits in nature.