Journal of Evolutionary Biology最新文献

Climate change is known to influence biodiversity worldwide, with changes in organismal traits observed in many populations and species. Such effects are not universal, however, with some traits showing remarkable stability through time. Time-series analyses that link environmental variables to trait values can generate useful insights into trait evolution and its ecological bases. We use 24 years of data for beak and body traits in two species of Darwin's finches in the Galápagos Islands, alongside data on temperature and precipitation, to answer three questions: (Q1) is climate change present in our study sites? (Q2) do time-series of beak and body traits show detectable trends that suggest climate change effects? and (Q3) to what extent does weather influence annual variation in beak and body traits? We found that temperature and precipitation have been increasing over the past two decades-although this trend is minor in comparison to year-to-year variation. We next found that time-series of beak and body traits showed no detectable signs of climate change impact, instead they behave either as random walks or stable trajectories. Finally, for both species, analyses for short-term responses show that precipitation has a lagged, negative correlation with beak and body traits (effect size: maximum -0.632, minimum -0.131). Increased precipitation followed smaller traits in subsequent years. Associations of finch traits with temperature were more variable. We discuss reasons why Darwin's finches react to short-term weather changes but not to long-term climatic trends, and how these results relate to other findings in other tropical systems.

In the wild, every population exhibits a certain degree of spatial structure. Some populations are subdivided into demes, between which individuals may disperse. Dispersal ability is influenced by certain mutations, which can also affect vital traits such as birth and death rates. To quantify the impact of population subdivision on the evolutionary dynamics of such mutations, we derive their fixation probability in both the island and stepping-stone models. Our analytical derivations highlight an effective selection coefficient, which quantifies how differences in vital and dispersal traits between the mutant and wild type contribute to the mutant's spread. We also examine how other quantities, such as fixation time, are influenced by mutations that affect both vital and dispersal traits.

Dispersal syndrome, which describe covariation of dispersal traits with other traits, provide clues for potential selection pressures or evolutionary constraints imposed on dispersal. In plants, theory predicts various associations of dispersal traits with fecundity and clonal expansion, but dispersal syndromes involving these reproductive traits are empirically underexplored. This study examined the associations of two dispersal traits (elaiosome size, autochorous distance) with two reproductive traits (fecundity, clonal expansion) among 40 sedges species (Carex spp.), that disperse seeds through autochory, specifically postfloral stalk bending and growth, followed by myrmecochory. Of the two dispersal traits, longer autochorous distances are expected to reduce local seed clumping, while larger elaiosomes are known to result in longer dispersal distances through attraction of large ants. The PCA analysis using all dispersal and reproductive traits followed by the cluster analysis revealed three groups of sedge species. Of these, group 1 appears to be specialized for longer myrmecochorous distances, and consists of phalanx species with large elaiosome, low fecundity, and short autochorous distance. The other two groups appear to be more specialized for short-distance dispersal with local scattering by means of either the combination of long autochorous distance and high fecundity (group 2) or the clonal expansion (group 3). These trait association is consistent with the functional redundancy of the traits in risk spreading and/or the fecundity cost of producing larger elaiosomes. Moreover, the finding is among the first to show an existence of dispersal syndromes among myrmecochorous plants involving dispersal and reproductive traits.

Biological individuality exists in different forms-unicellular, multicellular, colonial, etc.-which have arisen through evolutionary transitions in individuality. These involve bundling separate, lower-level individuals (particles) into higher-level ones (collectives) that transition to being individuals in their own right. What it is that "transitions" in the process is an open question inviting different answers, based on distinct conceptual accounts of biological individuality. We argue that evolutionary transitions in individuality always produce "paradigmatic" individuals, i.e., those identified as individuals under any concept. This renders distinguishing among individuality concepts moot, yielding two negative consequences. First, it has let evolutionary biologists refrain from declaring what kind of individuality they speak of in the evolutionary transitions in individuality, which has led them to talk past one another. Second, it has made them overlook the possibility that transitions may revert. Drawing on different individuality concepts, we identify two conceptually-different ways for collectives to "lose" their individuality. Paradigmatic reversions involve the complete undoing of a former evolutionary transition in individuality, e.g., a shift from multicellularity to unicellularity. Agential reversions do not involve such an organizational shift-a multicellular organism remains multicellular-but rather see the level at which selection and adaptation prevails change. Whereas paradigmatic reversions could also be caused by ecological shifts, agential reversions can occur only through internal conflict, where different particles within a collective have mutually-exclusive evolutionary interests. We conclude by discussing how reversions help create a more elaborate and accurate understanding of individuality and its evolution.

Environmental changes threaten the persistence of wild populations and can drive adaptive phenotypic changes. However, predicting the phenotypic outcome of an environmental change based on features of the species remains challenging. Genome size has been linked to variables that could influence the amount and rate of phenotypic change on contemporary time-scales. Two contrasting hypotheses have been proposed. The first suggests that larger genome sizes are associated with greater amounts and rates of phenotypic change, due to increased genetic variance and phenotypic plasticity. The second suggests the opposite based on the negative effect of genome size on both generation time and cell duplication time. We tested these two hypotheses using the Phenotypic Rates of Change Evolutionary and Ecological Database. We analyzed the relationships among genome size, phenotypic trait variability, mean trait change, and generation time. We found no support for the either of the tested hypotheses. Overall, the genome size explained less than 2% of the total variance in the amount of phenotypic change. In plants only, we found a consistent and negative effect of genome size on phenotypic change. However, we found no relationship between genome size and generation time, and we found no relationship between genome size and phenotypic variance. However, the consistent and relevant effect of phenotypic variance on the mean-scaled phenotypic change is worth highlighting from a conservation perspective because assessing the phenotypic variability of traits related to the niche breadth in different dimensions could inform us about the vulnerability of natural populations facing unexpected environmental changes.

Alternative reproductive tactics often involve trade-offs between mating success and survival to sexual maturity, resulting in differential investment in shared traits driven by disruptive selection. Selection on intrinsic growth can lead to individuals optimizing mating success by delaying maturation, with others maturing precociously and at smaller sizes. Such trade-offs can continue post maturation and may differ between tactics or life histories. To examine differential investment in growth and reproduction, we explored relationships between body length and reproductive success in cuckolders, and compared body length and intrinsic growth in male (cuckolder vs parental) bluegill sunfish, Lepomis macrochirus. Reproductive success in cuckolders was highest at smaller (sneaker) and larger (satellite) body sizes. Cuckolders were larger than parentals in the first two years of life but not from year 3 onward, and growth trajectories varied significantly between cuckolder and parental life histories. Despite the early size advantage, cuckolders grew slower during early age transitions (1+→2+, 2+→3 + years), likely reflecting investment in sexual maturation. In subsequent years (3+→4 + and 4+→5+), cuckolders showed comparable growth to parentals despite parentals remaining immature. Cuckolders thus appear to persist through a phase of lower reproductive success at intermediate sizes by differentially investing in growth. Our results suggest that the alternative reproductive tactics in bluegill are driven in part by body size at age 1, with larger body size being a prerequisite for precocial maturation (adoption of the cuckolder life history). After initial investment in sexual maturation, cuckolders then re-prioritize growth during body sizes associated with lower reproductive success.

Intracellular endosymbionts such as Wolbachia are generally thought to persist in host populations by inducing reproductive phenotypes that enhance maternal transmission, often at the expense of male hosts. Here, we examined the fitness consequences of the Wolbachia strain wStv in Drosophila sturtevanti, a highly abundant Neotropical drosophilid. Samples from 2015 and 2016 showed that all individuals from the nearby sampled populations carried Wolbachia, suggesting the induction of a phenotype capable of maintaining high infection levels. We therefore established isofemale lines from a local population and used one of them in controlled crosses between infected and treated flies to assess symbiont-induced changes in reproduction within a single genetic background. Contrary to expectations, we detected no cytoplasmic incompatibility or other reproductive manipulation. Instead, infection decreased female fecundity and decreased larvae production in crosses with treated males. Additional samplings in 2019 and 2022 showed that the infection persists in the population, and wsp sequencing confirmed that all infections detected from 2015 to 2022 carried the same allele. We also found imperfect but high maternal transmission, which may help to explain both the high infection levels observed in 2015-16 and the persistence of the infection. Our findings provide a foundation for future studies seeking to understand this association more broadly. They also reveal that Neotropical host-symbiont interactions can involve unexpectedly complex dynamics, indicating that the processes traditionally used to explain Wolbachia persistence may not be sufficient in this system.

Variation in traits expressed during social interactions can be attributed to direct individual effects (DIEs) of the focal individual's identity and indirect individual effects (IIEs) of social partner identity. When of genetic origin and covarying with direct effects, indirect effects affect the expressed variation upon which selection can act; this can explain why evolution is slower or faster than predicted by classic theory. Little is known about how DIEs and IIEs covary across traits, even though such relationships should affect micro-evolutionary trajectories. We also do not know whether IIEs change over time or contexts. Here we tested game theoretical predictions of producer-scrounger tactic use during social foraging games in wild house sparrows (Passer domesticus). We used automated high-throughput phenotyping, where we assayed individuals repeatedly against different social partners. We provide evidence for IIEs and DIEs in producer-scrounger behaviour, and high cross-year repeatability. Both IEEs and DIEs were correlated among traits: producers depressed producing-but elicited increased scrounging-in others, and vice versa. This structure likely strongly constrains behavioural evolution. Indirect effects decreased the phenotypic variation in both behaviours. IEE-DIE correlations among and within traits may thus explain the long-term maintenance of stable social foraging strategies.

Subterranean environments provide unique habitats and maintain numerous biodiversity. However, their underlying evolutionary processes remain poorly understood, and especially complex evolutionary hypotheses have not been tested or documented well. In this study, we investigate the evolutionary origin of spatially isolated groups of the subterranean amphipod Pseudocrangonyx (Crustacea: Amphipoda: Pseudocrangonyctidae) within a single cave (Fusa Cave) in northeastern Japan. To archive this goal, we conducted phylogenetic and population genetic analyses using mitochondrial and nuclear markers, as well as genome-wide single nucleotide polymorphisms (SNPs), with enhanced taxon sampling primarily from northeastern Japan. Both analyses revealed that the isolated group was genetically distinct from another group within Fusa Cave, and that both populations were genetically related to another group of an adjacent cave (Kuma-ana Cave). In addition, migration analysis estimated limited gene flow among these populations. Demographic simulations based on SNPs suggested that the isolated population diverged first, followed by the differentiation of the two cave populations. Then, a secondary contact-likely involving hybridisation- occurred within Fusa Cave, resulting in the observed genetic similarity. Our findings suggest that complex evolutionary histories, including secondary contact is more likely than apparent sympatric or micro-allopatric diversification. This study emphasises the importance of considering complex evolutionary hypotheses in subterranean diversification and highlights the value of genome-wide approaches combined with multiple types of analyses for uncovering hidden evolutionary scenarios.

Fertilisation success is a major component of male fitness, meaning males should capitalise on all opportunities for mating. However, other sources of variation in fitness mean that males often evolve life histories that limit their ability to mate frequently. We quantified mating latency, mating duration, and offspring production in males of the tropical fly Drosophila birchii when presented with up to 4 females consecutively. Males were sourced from isofemale lines from the extremes of 2 elevational gradients (20-1100 m) that show substantial differences in population density, temperature, and humidity. Total offspring sired increased with number of matings achieved, demonstrating substantial benefits of multiple mating. However, mean numbers of offspring declined with each successive mating, and mean mating durations increased, while mating latencies remained consistent. We saw no reduced fitness in male offspring from later matings, suggesting that declining offspring production is not associated with decreasing quality. Although differences between gradients were observed in total offspring production, reductions in offspring number were as great for males from high density sites as those from low density sites, despite expectations that males from high density sites would show higher mating investment. We also detected no divergence between high and low elevation sites for other traits, suggesting little adaptive divergence in mating strategies across this species' entire elevational range. The steep decline in offspring production over successive matings may reflect low encounter rates, or mating opportunities with females in natural populations of this species, even in high density environments, reducing relative investment in sperm or ejaculates.