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

Grandmothers are often presented as key carers due to low costs and high inclusive fitness returns. Empirically, however, grandmothers are not consistently important. Understanding the factors that promote, or hinder, grandmothering is an important next step. We explore the demographic predictors of the low levels of grandmothering in Agta hunter-gatherers (78 children with 29 grandmothers). Due to generational reproductive timing, grandmothers still had dependent children until, on average 52, creating reproductive overlap. The minimal levels of grandmaternal investment after the age of 60 are explained by declining health and high mortality. This means the 'helping window' for grandmothering only spans 7 years. Yet grandmothers are still limited by multiple dependent grandchildren in this period, given high fertility. We suggest then that Agta grandmothering is constrained by (i) reproductive overlap and (ii) grandchildren competition. Accordingly, we tested how (i) the number of children and (ii) grandchildren associated with grandmothering using Bayesian mixed-effect models. We found moderate to strong evidence that more children/grandchildren reduced investment in each grandchild. Consequently, whether Agta grandmothers help appears dependent on demographic schedules, which vary widely both within and between populations. Future formal demographic modelling will then help shed light on the evolution of grandmothering in humans.

Traditional biomarkers, such as those obtained from blood tests, are essential for early disease detection, improving health outcomes and reducing healthcare costs. However, they often involve invasive procedures, specialized laboratory equipment or special handling of biospecimens. The retinal age gap (RAG) has emerged as a promising new biomarker that can overcome these limitations, making it particularly suitable for disease screening in low- and middle-income countries. This study aimed to evaluate the potential of the RAG as a biomarker for broad disease screening across a vast spectrum of diseases. Fundus images were collected from 86 522 UK Biobank participants aged 40-83 (mean age: 56.2 ± 8.3 years). A deep learning model was trained to predict retinal age using 17 791 images from healthy participants. The remaining images were categorized into disease/injury groups based on clinical codes. Additionally, 8524 participants from the Brazilian Multilabel Ophthalmological Dataset (BRSET) were used for external validation. Among the 159 disease/injury groups from the 2019 Global Burden of Disease Study, 56 groups (35.2%) exhibited RAG distributions significantly different from healthy controls. Notable examples included chronic kidney disease, cardiovascular disease, blindness, vision loss and diabetes. Overall, the RAG shows great promise as a cost-effective, non-invasive biomarker for early disease screening.

Understanding how environmental and human pressures impact the temporal stability of fish community biomass on shallow reefs is essential for effective conservation and management. These pressures influence community stability directly, by affecting species' stability and asynchrony in species' fluctuations. However, their effects may also indirectly depend on the functional traits of the species composing the community, which remains poorly understood. Here, we examine both direct and indirect, trait-mediated effects of environmental variability and human impacts on species' biomass stability and asynchrony in 215 Australian shallow reefs. These communities span a 10-degree sea surface temperature (SST) gradient and have been monitored over 14 years. Our results indicate higher asynchrony in tropical reefs owing to higher trait diversity and trait redundancy and higher species' stability in colder, temperate communities owing to higher mean trophic level. Human impacts, through their negative effects on species' stability and trait diversity, were the main destabilizing factor of fish community biomass. Temporal change in SST destabilized species' biomass while increasing mean trophic level in fish communities. Overall, our findings show that a comprehensive analysis of the multiple facets of functional diversity is crucial to better understand and forecast the long-term stability of marine ecosystems under global change.

Individuals vary in their stress-coping styles, characterized by specific behavioural and physiological traits that influence their response to stressors. Theory suggests that these traits are linked to underlying metabolic mechanisms that affect energy management strategies. Despite the potential of this powerful comparative approach, few studies have explored how stress-coping styles relate to energy management strategies. Using heart rate telemetry data from a large, capital-breeding pinniped, the grey seal (Halichoerus grypus), we sought to investigate the relationship that stress-coping styles (via individual resting heart rate variability, rHRV) may have on energy management strategies. Background energy expenditures, a proxy for metabolic rate and other background processes, and daily energy expenditures were found to be individually repeatable in grey seal mothers across successive breeding seasons. Proactive individuals (low rHRV) exhibited consistently higher background and daily energy expenditures than reactive females (high rHRV). However, reactive phenotypes were more variable overall in energy management strategy, highlighting greater flexibility in their energy management strategy. Our results highlight key energetic trade-offs associated with stress-coping styles in grey seal mothers during this short but critical life-history stage; proactive individuals tended to exhibit a single pattern of energy management, expending greater energy while incurring greater risk of over-spending, than those with a more reactive phenotype.

Spatial context is critical for telling how big a visual object is, although it may also cause the perceived size to diverge dramatically from the true dimensions. Interestingly, responses in the primary visual cortex (V1) mirror such illusory perception; however, the stage of processing that leads to such neural correlates remains unknown. Here, we tested the involvement of higher level processing in a Ponzo-like illusion, by quantifying the effect of manipulating depth cues and inversion of the whole scene. We report a stronger illusion for realistic compared with simpler backgrounds, and for upright compared with inverted scenes (except for scenes where the target objects appeared on the ceiling or in the sky). Next, using functional MRI, we tested the effect of inversion on V1 responses. Inverted scenes elicited a smaller extent of activation in V1 compared with upright scenes, consistent with their perceived sizes. Taken together, since the inversion should disrupt the high-level processing while keeping the low-level features intact, our findings demonstrate that Ponzo-like illusions involve high-level processes that integrate contextual depth cues and visual experience, thereby modulating the object's neural representation in V1.

Identifying key drivers of insect diversity decline in the Anthropocene remains a major challenge in biodiversity research. Metabarcoding has rapidly gained popularity for species identification, yet the lack of abundance data complicates accurate diversity metrics like sample coverage-standardized species richness. Additionally, the vast number of taxa lacks a unified phylogeny or trait database. We introduce a new workflow for metabarcoding insect data that constructs a phylogenetic tree for most insect families, standardizes sample coverage and assesses both taxonomic and phylogenetic diversity along the Hill series. Applying this workflow to Central Europe, we analysed insect diversity from 400 families across a land-use gradient. Our results show that land-use intensity significantly affects sample coverage, highlighting the necessity of biodiversity standardization. Taxonomic diversity declined by 27-44% and phylogenetic diversity by 13-29% across 39 000 operational taxonomic units, with diversity decreasing from forests to agricultural areas. When focusing on rare species communities exhibited greater phylogenetic diversity loss than taxonomic diversity, whereas dominant species experienced smaller phylogenetic losses but more pronounced declines in taxonomic diversity. Our findings underscore the detrimental effects of agriculture on insect taxa and reveal a dramatic loss of phylogenetic diversity among rare species with potential consequences for ecosystem stability.

Extremophiles survive in environments that are considered uninhabitable for most living things. The evolution of extremophiles is of great interest because of how they may have contributed to the assembly of ecosystems, yet the evolutionary dynamics that drive extremophile evolution remain obscure. Here, we investigate the evolution of extremophiles in Zoarcoidea, a lineage of over 300 species of fishes that have colonized both poles, the deep sea, and hydrothermal vents. We show that a pulse of habitat invasion occurred across over 20 different zoarcoid lineages within the last 8 million years, far after the origin of their prototypical innovation for surviving in cold water: type III antifreeze protein. Instead, a secondary burst of anatomical, physiological and life history traits and a handful of founder events in extreme ecosystems appear to have propelled zoarcoid diversification. These results decentralize the role of prototypical changes to organismal biology in shaping extremophile radiations and provide a clear example of how a combination of ancient adaptations and recent contingency shapes the origination of lineages in challenging habitats.

Elaborate traits evolve via intense selective pressure, overpowering ecological constraints. Hindwing tails that thwart bat attack have repeatedly originated in moon moths (Saturniidae), with longer tails having greater anti-predator effect. Here, we take a macroevolutionary approach to evaluate the evolutionary balance between predation pressure and possible limiting environmental factors on tail elongation. To trace the evolution of tail length across time and space, we inferred a time-calibrated phylogeny of the entirely tailed moth group (Actias + Argema) and performed ancestral state reconstruction and biogeographical analyses. We generated metrics of predation via estimates of bat abundance from nearly 200 custom-built species distribution models and environmental metrics via estimates of bioclimatic variables associated with individual moth observations. To access community science data, we developed a novel method for measuring wing lengths from un-scaled photos. Integrating these data into phylogenetically informed mixed models, we find a positive association between bat predation pressure and moth tail length and body size, and a negative association between environmental factors and these morphological traits. Regions with more insectivorous bats and more consistent temperatures tend to host longer-tailed moths. Our study provides insight into tradeoffs between biotic selective pressures and abiotic constraints that shape elaborate traits across the tree of life.

Maternal care can maximize offspring survival and may contribute to the establishment success of invasive species. The brown widow spider, Latrodectus geometricus, is a successful invader worldwide. Here, we investigated the role of maternal care in enhancing its success. We compared the defence mechanisms of the invasive L. geometricus with those of another widow spider native to the Negev desert, Latrodectus pallidus, against an egg sac parasitoid wasp. Both spider species exhibited guarding behaviours following exposure to wasps; however, only L. geometricus efficiently evaded and successfully killed the parasitoid. Accordingly, its egg sacs were parasitized less frequently than those of L. pallidus. Next, we evaluated the defensive role of the silk spike-like structures on L. geometricus egg sacs. When spikes were removed from half of the egg sac surface, the wasps laid more eggs on the spike-free side. In an additional experiment, L. geometricus females increased spike density on subsequent egg sacs after exposure to the parasitoid. We showed that L. geometricus employs both behavioural defences and modifications to the egg sac structure to protect against the parasitoid. These defences may provide L. geometricus with an advantage over native species in its invasive range, potentially contributing to its invasion success.