Proceedings of the Royal Society B: Biological Sciences最新文献

Long-term records that span the past several centuries and capture within-population variation are critical for distinguishing ephemeral ecosystem changes from regime shifts. Using an approximately 2 kyr record of reproductive life history from the central Santa Barbara Basin, we examined population trends in reproductive mode and accumulation rate (i.e. reproductive output) across four species in the biserial benthic foraminiferan genus Bolivina. Bolivina populations were consistently dominated by asexually produced individuals until the mid-nineteenth century, after which they exhibit an increase in variance and a decrease in the mean proportion of asexually produced individuals. At the same time, they underwent an order-of-magnitude decline in accumulation rate. The magnitude and persistence of these changes suggest that the nineteenth and twentieth centuries represent a life-history regime shift. The compounding effects of anthropogenic impacts and long-term trends in the California Current System (such as heightened deoxygenation and altered sedimentation regimes) may have pushed the Santa Barbara Basin towards increased investment in sexual reproduction.

Understanding the patterns and drivers of viral prevalence and abundance is of key importance for understanding pathogen emergence. Over the last decade, metagenomic sequencing has exponentially expanded our knowledge of the diversity and evolution of viruses associated with all domains of life. However, as most of these 'virome' studies are primarily descriptive, our understanding of the predictors of virus prevalence, abundance and diversity, and their variation in space and time, remains limited. For example, we do not yet understand the relative importance of ecological predictors (e.g. seasonality and habitat) versus evolutionary predictors (e.g. host and virus phylogenies) in driving virus prevalence and diversity. Few studies are set up to reveal the factors that predict the virome composition of individual hosts, populations or species. In addition, most studies of virus ecology represent a snapshot of single species viromes at a single point in time and space. Fortunately, recent studies have begun to use metagenomic data to directly test hypotheses about the evolutionary and ecological factors which drive virus prevalence, sharing and diversity. By synthesizing evidence across studies, we present some over-arching ecological and evolutionary patterns in virome composition, and illustrate the need for additional work to quantify the drivers of virus prevalence and diversity.

Sexual selection shapes the genome in unique ways. It is also likely to have significant fitness consequences, such as purging deleterious mutations from the genome or conversely maintaining genetic load in a population via sexual conflict. Here, we examined what the influence of sexual selection has on genomic variation potentially underlying population fitness using experimentally evolved Drosophila pseudoobscura populations. Sexual selection was manipulated by keeping replicate lines in elevated polyandry or strict monogamy for approximately 200 generations followed by individual-based sequencing. Using pi (π), fixation index (F_st)and recombination rate measures, we confirmed signatures of selection were not dispersed but mainly localized to the third and X chromosome. Overall mutational load was similar between lines but our analysis of the distribution of fitness effects revealed considerable variation between lines and chromosomes. Furthermore, we found that the distribution of transposable elements differs between the lines, with a higher load in monogamous lines. Our results suggest that complex interactions between purifying selection and sexual conflict are shaping the genome, particularly on chromosome 3 and the sex chromosome; sexual selection influences divergence across chromosomes but in a more complex way than proposed by simple 'purging' of deleterious loci.

Aggression is a key determinant of fitness in many species, mediating access to mates, food and breeding sites. Variation in intrasexual aggression across species is likely to be driven by variation in resource availability and distribution. While males primarily compete over access to mates, females are likely to compete over resources to maximize offspring quantity and/or quality, such as food or breeding sites. To date, however, most studies have focused on male aggression, and we know little about drivers of female aggression across species. To investigate potential reproductive drivers of female aggression, we tested the relationship between three reproductive traits and aggression in eight Drosophila species. Using machine learning classifiers developed for Drosophila melanogaster, we quantified aggressive behaviours displayed in the presence of yeast for mated and unmated females. We found that female aggression was correlated with ovariole number across species, suggesting that females who lay more eggs are more aggressive. A need for resources for egg production or oviposition sites may therefore be drivers of female aggression, though other potential hypotheses are discussed.

In recent years, the case for the monophyly of mites or Acari (Parasitiformes + Acariformes) has looked increasingly weak. Much of the remaining doubt about the artificiality of this taxon stems from the importance long attributed to the gnathosoma, widely considered the most convincing morphological character supporting monophyly. The gnathosoma has long been interpreted as originating via the fusion together of the palpal coxae, which is thought to have contributed to the consolidation of the mouthparts into a compact feeding apparatus that articulates as a single unit. However, an investigation of the mouthparts of Acariformes, reported herein, revealed that fusion together of the palpal coxae is an uncommon state that convergently evolved in multiple acariform taxa rather than evolving only once, as a synapomorphy uniting Acariformes and Parasitiformes. Moreover, other defining features of the gnathosoma involve either very different modifications or structures that are not homologous between both main lineages of mites. Therefore, the gnathosoma is a bad character-poorly defined and based on a series of misinterpretations-that should not be treated as evidence for mite monophyly.

When the Darwinian interests of genes in the genome collide, intragenomic conflicts evolve. Recent advances in social evolution predict that intragenomic conflicts shape diverse phenotypes. However, principles governing which side wins remain unresolved. Here, we use game theory to predict that power asymmetries arise from differences in appetite for risk between rival genes in 'wars of nerve'. We focus on 'genomic imprinting': differing expression between alleles inherited from mothers and fathers. Escalating conflict is commonly believed to risk damaging the whole organism. We show that genes can exploit risk strategically: genes prepared to take greater risks with the body's vulnerability to disorders and mortality gain coercive advantages, deterring countermoves. Kin selection generates differences in appetite for risk: for instance, if harm to the body frees resources for maternal siblings, genes from mothers have less to lose from gambling with the current body than do genes from fathers. Seemingly maladaptive developmental risks can be adaptively useful for higher-nerve genes, much as political states manipulate risk to coerce rivals. Our results suggest a determinant of power alongside the 'loudest voice prevails' principle, and call for empirical investigation of the extent and means by which risks of imprinting-related disorders are amplified by intragenomic brinkmanship.

The evolution of thermoreception in animals, particularly that of infrared (IR)-sensing pits in boas, pythons and pit vipers, is a fascinating area of sensory ecology. While numerous studies have focused on the molecular mechanisms of IR sensing in snakes, the broader ecological and evolutionary significance remains less explored. In this study, we examined the origins and evolutionary consequences of labial pits in boas and pythons using phylogenetic comparative methods. We analysed how various ecological and biological factors-such as hunting mode, diet, habitat, body size and biome-were correlated with the presence of pits, and whether this adaptation influenced diversification rates. Our findings revealed that labial pits evolved multiple times and showed strong associations with an arboreal habitat and endothermic diet, but we did not find a significant correlation between pits and hunting mode or any other ecological traits. Moreover, lineages with pits did not exhibit higher diversification rates. This research provides new insights into the eco-evolutionary role of heat-sensing pits, suggesting that the emergence of labial pits might have acted as a key innovation, significantly affecting the evolution of habitat use patterns and prey preference for pythons and boas.

Performance tends to decline with age, including muscle function and stress tolerance. Yet, performance can vary widely among individuals within the same age group, showing that chronological age does not always represent biological age. To better understand ageing, we need to examine what drives some individuals to age faster than others. In order to achieve this, first we need to be able to predict whether an individual will have a long or short lifespan. In this study, we conducted a longitudinal study tracking individual-level locomotor activity, chill-coma recovery time, and metabolic rates, and assessed whether early-life performance is linked to lifespan using the solitary bee Megachile rotundata. We found that locomotor activity and chill-coma recovery times decline in old adults. However, resting metabolic rate did not change with age. We also found low cold tolerance and low mass at emergence in early-life are linked to shorter female lifespans, showing that early-life performance can explain some of the variation in lifespan in a population. Finally, these results also show that not all traits decline with age within the same species, and shed new light on sexual dimorphism in physiological traits and ageing.

The gut microbiota significantly influence host health by impacting metabolism, immune function and development. Understanding bacterial behaviours in intestinal folds is crucial owing to their role in biofilm formation, which protects bacteria from immune responses and antibiotics and is associated with colorectal cancer. In this study, we observed the behaviours of Escherichia coli bacteria in the intestinal folds of zebrafish larvae (Danio rerio). It is found that E. coli swims in the intestinal folds for extended periods and is confined in a groove on the wall. In order to clarify the mechanism of the confinement, we further performed numerical simulations using a boundary element method. Our simulations demonstrate that bacterial movement in the groove is constrained by hydrodynamic and steric forces. The groove configuration significantly influences bacterial confinement, with bacteria in a deep groove escaping more easily in the presence of background flow. Based on the aggregation rate of E. coli in the intestinal folds of zebrafish larvae, it is indicated that the groove trapping significantly reduces cell flux away from the wall. These findings enhance our understanding of bacterial accumulation and biofilm formation in the gut, with implications for other environments with geometric constraints.

We document two profoundly different specialized swimming modes in two ancient lineages of water scavenger beetles (Hydrophilidae): (i) the upside-down swimming using middle legs in the species-poor Amphiops and (ii) the dorsal-up swimming using middle and hind legs in the species-diverse lineage of all other actively swimming taxa, including Berosus analysed here. Both lineages share a unique modification of the mesofurca supporting the leg swimming movements, indicating a single origin of swimming. By behavioural experiments and biomechanical analyses, we reveal that the swimming of Amphiops is optimized for high manoeuvrability, whereas that of Berosus for speed and acceleration. Both swimming modes differ in the form of the meso- and metathoracic skeleton and leg musculature, excluding the possibility that one is derived from the other. Behavioural experiments indicate that both modes are adaptive morpho-functional peaks and that intermediate modes are suboptimal. This aligns with the phylogeny-based model comparison that indicates that both swimming modes have evolved from an ancestral swimming lost in modern beetles. The multi-method approach helps us to reconstruct ancient behaviour and identify trade-offs that shaped the evolution of lifestyles in Mesozoic aquatic beetles.