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

Climate change will affect precipitation and water availability in natural plant populations, potentially influencing phenology, fitness and natural selection. To examine how water availability affects non-pollinator- and pollinator-mediated selection on flowering phenology in Primula tibetica, we manipulated pollination at three sites that differed in soil water content (low, medium and high) in a single common garden. We detected conflicting selections on phenology. At low water content, there was pollinator-mediated selection for earlier flowering start and non-pollinator-mediated selection for later start. At medium water content, pollinators selected for shorter flowering duration and non-pollinator agents for longer duration. The opposing selection resulted in no statistically significant net selection on phenology. Non-pollinator-mediated selection differed between sites, and changes in trait-fitness relationships among hand-pollinated plants were mainly driving variation in selection on phenology. The results indicate that soil water content primarily affects selection on phenology via resource uptake, and are consistent with higher pollinator abundance or constancy early in the flowering season. The study highlights that both flowering start and duration can be targets of selection, that phenology may be subject to conflicting selection from pollinators and other agents, and that the evolution of flowering time in response to pollinator-mediated selection can be constrained by climate.

Climate and land-use change are major drivers of insect decline, yet their interactive effects on insect richness and abundance, especially across trophic levels, remain poorly understood. Here, we investigate how temperature and land use shape insect communities across spatial scales and trophic levels, from flowering plants and cavity-nesting bees to hunting wasps, their antagonists and parasitism rates. Using trap nests and a space-for-time approach, we surveyed 179 plots spanning four habitat types (forest, grassland, arable land and settlements) across 60 study regions in Germany covering semi-natural, agricultural and urban landscapes. Bee richness and abundance responded to climate-land-use interactions across spatial scales, being higher with warmer local daytime temperatures and overall warmer climates, but only in less intensive land uses. In contrast, elevated night-time temperatures negatively affected bees. Higher trophic levels benefited more consistently from warmer climates than lower trophic levels and were less affected by high local daytime and night-time temperatures. Parasitism rates were lowest in arable land but similar across habitats within semi-natural regions, suggesting that landscape-scale processes buffer local effects. Our findings underscore the importance of considering night-time temperatures for diurnal insects and suggest that rising temperatures may exacerbate the negative impacts of land use on pollinators.

DNA metabarcoding of species-rich taxa is becoming a popular high-throughput method for biodiversity inventories. Unfortunately, its accuracy and efficiency remain unclear, as results mostly pertain to poorly known taxa in underexplored regions. This study evaluates what an extensive sampling effort combined with metabarcoding can tell us about the lepidopteran fauna of Sweden-one of the best-understood insect taxa in one of the most-surveyed countries of the world. We deployed 197 Malaise traps across Sweden for a year, generating 4749 bulk samples for metabarcoding, and compared the results to existing data sources. We detected more than half (1535) of the 2990 known Swedish lepidopteran species and 323 species not reported during the sampling period by other data providers. Full-length barcoding confirmed three new species for the country, substantial range extensions for two species and eight genetically distinct barcode variants potentially representing new species, one of which has since been described. Most new records represented small, inconspicuous species from poorly surveyed regions, highlighting components of the fauna overlooked by traditional surveying. These findings demonstrate that DNA metabarcoding is a highly efficient and accurate biodiversity sampling method, capable of yielding significant new discoveries even for the most well known of insect faunas.

Mothers play a crucial role in the early development and survival of mammalian offspring, and differences in maternal care may affect offspring's development. Whereas previous research has primarily focused on biological and socioecological factors to understand population-level variation in maternal behaviour, the individual as a source of variation remains understudied. We investigated between-individual variation in the average expression of, and plasticity in, six maternal behaviours in Sumatran orangutans (Pongo abelii), using 15 years of behavioural data. We found that mothers differed substantially in the average expression of four maternal behaviours, even after controlling for socioecological conditions, biological state characteristics and the offspring's influence on these behaviours. Furthermore, not controlling for these confounding effects exaggerated or masked between-individual variation. Mothers also substantially differed in how they adjusted three of the maternal behaviours during offspring development, meaning that mothers differed in behavioural plasticity. Our results suggest that Sumatran orangutan mothers are constrained in the average expression of maternal behaviours and their plastic responses, potentially resulting in consistent differences among mothers, otherwise called maternal personality. Our findings highlight that there is biologically meaningful variation around the population mean in maternal behaviour and present novel opportunities to study evolutionary processes that shape maternal behaviour.

Social hierarchies in sex-changing fish determine which fish will change sex, yet the complexities of hierarchy formation at the neurobehavioural level are still being unravelled. Here, we investigate the formation of social hierarchies within groups of New Zealand spotty wrasse, integrating behavioural observations with neural activation patterns upon social disruption. We find that dominance hierarchies form linearly based on size, with larger fish displaying more dominant behaviours and smaller fish displaying more submissive behaviours. Disruption of the social hierarchy induced rapid behavioural changes, particularly in second-ranked fish, highlighting that second-ranked fish will opportunistically adopt a dominant position. Analysis of neural activation patterns reveals that the social decision-making network is deeply involved in the establishment of dominance, with the fish attaining dominance showing significant differences to all other ranked fish. Overall, this study underscores the complexity of social relationships and their neural underpinnings in the spotty wrasse, providing a foundation for further research into the cellular and molecular mechanisms of socially controlled sex change, and demonstrates that disruption of the social hierarchy triggers rapid changes in both behaviour and the social decision-making regions of the brain.

Environmental heterogeneity is widely thought to promote biodiversity, yet its variable effects limit its predictive power. This variability can be better understood by considering key mediating factors: different forms of local heterogeneity, organismal groups and their associated traits, and the broader environmental context (e.g. latitude). To address these factors, we analysed 144 studies (24 412 data points and 2815 effects) from rocky reefs worldwide. Heterogeneity was defined as spatial variability, and heterogeneity metrics were grouped into facets such as three-dimensional (3D) structure (e.g. substrate rugosity), complexity (e.g. fractal dimension) and feature variability (e.g. mussel size classes). All facets promoted biodiversity, but effects were context-dependent, with 3D structures having the strongest impact, likely owing to increased niche provision and substrate area. Responses also varied across organismal groups, with small-bodied and mobile species benefiting the most. Additionally, heterogeneity reduced grazing and enhanced recruitment, helping promote biodiversity. Effects were strongest on biogenic substrates, at lower latitudes and in more stressful intertidal zones. Overall, the influence of local heterogeneity depends on how it is generated and measured, organisms' traits, and prevailing environmental conditions. These insights inform the development of a conceptual model predicting heterogeneity's context-dependent effects on biodiversity across systems.

The evolution of multicellular organisms involves the emergence of cellular collectives that eventually become units of selection in their own right. The process can be facilitated by ecological conditions that impose heritable variance in fitness on nascent collectives, with long-term persistence depending on the capacity of competing lineages to transition reliably between soma- and germ-like stages of proto-life cycles. Prior work with experimental bacterial populations showed rapid increases in collective-level fitness, with the capacity to switch between life cycle phases being a particular focus of selection. Here, we report experiments in which the most successful lineage from the earlier study was further propagated for 10 life cycle generations under regimes that required different investments in the soma-like phase. To explore the adaptive significance of switching, a control was included in which reliable transitioning between life cycle phases was abolished. The switch proved central to the maintenance of fitness. Moreover, in a non-switch treatment, where solutions to producing a robust and enduring soma-phase were required, the evolution of mutL-dependent switching emerged de novo. A newly developed computational pipeline (colgen) was used to display the moment-by-moment evolutionary dynamics of lineages, providing rare visual evidence of the roles of chance, history and selection. Colgen, underpinned by a Bayesian model, was further used to propagate hundreds of mutations back through temporal genealogical series, predict lineages and time points corresponding to changes of likely adaptive significance, and in one instance, via a combination of targeted sequencing, genetics and analyses of fitness consequences, the adaptive significance of a single mutation was demonstrated. Overall, our results shed light on the mechanisms by which collectives adapt to new selective challenges and demonstrate the value of genealogy-centred approaches for investigating the dynamics of lineage-level selection.

Bacterial infections are a major threat to public health. Pathogen host shifts-where a pathogen jumps from one host species to another-are important sources of emerging infectious diseases. However, compared with viruses, we know relatively little about the factors that determine whether bacteria can infect a novel host, such as how host phylogenetics constrains variation in pathogen host range and the link between host phylogeny and the infectivity and virulence of a pathogen. Here, we experimentally examined susceptibility to bacterial infections using a panel of 36 Drosophilidae species and four pathogens (Providencia rettgeri, Pseudomonas entomophila, Enterococcus faecalis, Staphylococcus aureus). The outcomes of infection differed greatly among pathogens and across host species. The host phylogeny explains a considerable amount of variation in susceptibility, with the greatest phylogenetic signal for P. rettgeri infection, explaining 94% of the variation in mortality. Positive correlations were observed between mortality and bacterial load for three out of the four pathogens. Correlations in susceptibility between the four pathogens were positive but largely non-significant, suggesting susceptibility is mostly pathogen-specific. These results suggest that susceptibility to bacterial pathogens may be predicted by the host phylogeny, but the effect may vary in magnitude between different bacteria.

The absence of terrestrial apex predators on oceanic islands led to the evolution of endemic secondary apex predators like birds, snakes and crocodiles, and loss of defence mechanisms among species. These patterns are well documented in modern and Quaternary terrestrial communities of the West Indies, suggesting that biodiversity there assembled similarly through overwater dispersal. Here, we describe fossils of a terrestrial apex predator, a sebecid crocodyliform with South American origins from the late Neogene of Hispaniola that challenge this scenario. These fossils, along with other putative sebecid specimens from Cuba and Puerto Rico, show that deep-time Caribbean ecosystems more closely resembled coeval localities in South America than those of today. We argue that Plio-Pleistocene extinction of apex predators in the West Indies resulted in mesopredator release and other evolutionary patterns traditionally observed on oceanic islands. Adaptations to a terrestrial lifestyle documented for sebecids and the chronology of West Indian fossils strongly suggest that they reached the islands in the Eocene-Oligocene through transient land connections with South America or island hopping. Furthermore, sebecids persisted in the West Indies for at least five million years after their extinction in South America, preserving the last populations of notosuchians yet recovered from the fossil record.

The footsteps illusion is a perceptual illusion in which two bars moving at the same constant speed on a stripey background are seen as alternately accelerating and decelerating like footsteps. The cortical mechanisms that give rise to footsteps and similar illusions remain to be fully understood and may reveal important neural computations. Using an implementation of the biologically inspired correlational model of motion detection, the 2-Dimensional Motion Detector, this study had three aims. First, reproducing perceptual speed oscillations in model simulations. Second, mapping empirical reports of multiple illusion configurations onto model outputs. Third, inferring from the successful model, the perceptual role of multi-scale spatio-temporal channels. We developed a 2-Dimensional Motion Detector implementation adding a global (single value) frame-by-frame dynamic readout to quantify continuous and oscillating response components. We confirmed that an expected signature oscillatory motion response corresponded to the footsteps illusion, demonstrating that its amplitude varied according to empirically measured illusion strength. We showed that with a global readout, the inherent pattern and contrast dependence of correlation detectors is sufficient to reproduce the surprising perceptual illusion. This evidence suggests spacetime correlation may be a fundamental sensory computation across species, with complementary filtering and global pooling operations adapted for various complex phenomena.