Journal of Evolutionary Biology最新文献

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.

Darwin argued that natural selection leads organisms to appear as if they are striving to maximise their fitness. This idea is readily recognised at the individual cell or body level, but such adaptive design may also manifest at some higher levels of biological organisation. Previous work has formalised the idea that social groups can be viewed as adaptive individuals in their own right-i.e., 'superorganisms'-under the assumptions that within-group selection is absent and that there is no class structure. However, the original and most common biological use of the term 'superorganism' is in reference to insect colonies in which members exhibit striking class structure in the form of reproductive division of labour. Accordingly, although obligately eusocial colonies are regularly conceptualised as having the capacity for colony-level adaptation, current formalisms are unable to support this idea. Here, we develop a formal theory of group-level adaptation for obligately eusocial colonies by establishing mathematical correspondences that connect the dynamics of natural selection-as described by Price's equation-to the mathematics of optimisation-wherein the colony is considered a fitness-maximising agent-under a range of assumptions as to which members of the colony control its phenotype and the degree to which they are genetically related.

Characterizing morphological variation along the vertebral column of mammals is commonly investigated at a broad phylogenetic scale, leaving within-species variation understudied due to the requirement of larger sample sizes. This leads to a knowledge gap of how variation within species relates to morphological diversity among species. Here, we overcome these limitations and examine the morphological variation at the within-species level in the vertebral column of 4 species-equivalent groups of rabbits and hares. We then expanded to the among-species levels of the family Leporidae, the order Lagomorpha, and broadly among terrestrial placentals. We sampled 9 vertebrae along the vertebral column of each specimen. Using a geometric morphometric approach, we calculated the Procrustes variance of vertebrae shapes and used this as an index for the extent of morphological variation of each vertebra along the vertebral column, which we call the profile. We find that the profile of morphological variation along the column differs among species and between phylogenetic levels; among-species variation is not simply a scaled-up profile of the within-species level. We highlight that by adopting the multi-level analysis, we can better understand how the mammalian vertebral column can evolve.

Batesian mimicry has been regarded as classic evidence of adaptation by natural selection, in which a palatable species avoids predation by resembling unpalatable species. In some butterfly species, Batesian mimicry is female-limited and mimetic females coexist with male-like (nonmimetic) females. Why do nonmimetic females continue to exist despite the possible differential predation pressure? One possible hypothesis is a trade-off between the anti-predatory defence and mating success. Specifically, mimetic females may be less attractive to conspecific males as they look like heterospecific butterflies. However, empirical studies based on behavioural data have shown mixed results. Here, we directly investigated female mating frequency by counting spermatophores and compared it between mimetic and nonmimetic females in a Batesian mimetic butterfly, Papilio polytes. The mating frequencies of the two types of females were almost identical in all four studied populations. More than 99% of females copulated at least once regardless of morph. In addition, the spermatophore counts increased with age and did not differ between morphs. Our results strongly suggest that the anti-predatory traits are unlikely to be costly to the reproductive success of mimetic P. polytes females, providing no support for the sexual selection hypothesis regarding maintenance of mimetic polymorphism.