Biology Letters最新文献

The human menopause is hypothesized to be an adaptive trait that allows post-reproductive females to invest in, and avoid reproductive conflict with, their existing offspring and grand-offspring, thereby increasing their survival. Thus, the sacrifice of an early cessation of reproduction can result in increased inclusive fitness. However, the genetic basis of menopause remains largely unknown. Given that a mid-life menopause is a rare trait in terrestrial social species, there is a need to consider alternative taxa to move beyond a single datapoint to test theoretical frameworks upon. One aquatic taxonomic group, toothed whales, comprises five matrilineal species with menopause, thereby providing a crucial comparative system for understanding the evolution of menopause. The kinship dynamics in killer whale Orcinus orca societies, maximize the inclusive fitness of post-reproductive females when they invest in their son's reproductive success. Specifically, inclusive fitness is maximized at the X-chromosome (over the autosomes) through a post-reproductive female's son siring daughters. This raises the question of how selection favours a female trait that primarily benefits male offspring? Due to its inheritance pattern and ploidy, the X-chromosome is a candidate target for sexual antagonistic selection, which could act on the female-specific traits of increased lifespan and reproductive cessation. We therefore propose that the X-chromosome is a promising marker to explore the genetic underpinning of menopause in matrilineal whale species and could provide a key comparison (and contrast) to the genetic basis of menopause in humans. Lastly, we expand these ideas to autosomal regions with female biased recombination.

In this study, we used a multi-faceted approach to understand patterns of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission and persistence in a wild white-tailed deer (Odocoileus virginianus) population. Serology data indicated transmission of SARS-CoV-2 and persistence during the seven-month sampling period. Traditional disease modelling based on deer-to-deer transmission indicated relatively low prevalence with an R0 of 1.9 and recovery period of 7 days; however, individual-based modelling informed by GPS tracked-movement data captured a potential transmission event. Phylogenetic analyses revealed a recurring pattern of divergent groups of deer-derived sequences with human-derived sequences falling close to each deer-derived cluster. Further, human-derived sequences were frequently sampled months prior to the deer-derived sequences, indicating repeated human to deer spillover. Using multiple types of data as well as both fine and broad scale analyses, we have characterized a pattern of localized outbreaks of SARS-CoV-2 within white-tailed deer populations that are likely recurring due to frequent spillover events. Our results suggest that while deer-to-deer transmission occurs over small spatiotemporal scales, SARS-CoV-2 persistence over longer periods and across larger regions is likely driven by repeated spillover from human populations.

Female preference for males with enhanced cognitive abilities has been reported in many species, but it remains unclear which sexual signals reflect such skills. We hypothesized that male dance performance is correlated with cognitive performance, body condition and increased attractiveness in zebra finches (Taeniopygia castanotis). We collected dance behaviours from 164 male displays and assessed male condition, attractiveness and performance in four cognitive tasks: associative learning, motor learning, spatial learning and inhibitory control. Variance in male displays was mainly explained by two independent features: dance duration and dance complexity. Dance duration was not correlated with male cognitive performance, body condition or attractiveness, while dance complexity was significantly linked with body condition and attractiveness and marginally linked with motor learning performance. While our findings suggest that male dance attributes are unlikely to serve as indicators of general cognition in zebra finches, dance complexity might reflect general health and may be used by females as a mate-choice criterion. Despite the need for replication, our findings do not support the idea that intersexual selection based on male dance displays shapes the evolution of general cognition.

Zoonotic spillover from wildlife to humans is a growing concern under rapid environmental change. Land use change is a major driver, altering habitats and creating new environments and opportunities for species interactions. Such changes can shift community composition, increase contact between humans and wildlife and provide susceptible hosts for pathogens, potentially leading to human transmission. In the Amazon, we examined how land use change affects spillover of yellow fever virus (YFV), a mosquito-transmitted virus with a primarily sylvatic cycle. Using two decades of municipality-level case data from Brazil, Peru and Colombia, along with high-resolution annual land cover data, we modelled the relationship between forest loss, fragmentation and YFV spillover using panel regression models. We found that forest fragmentation metrics previously linked to sylvatic YFV dynamics were not consistent predictors of spillover to humans. Instead, proximity of forests to urban areas-forest-urban interface-was a consistent and significant positive predictor of human YFV infection. While forest fragmentation and edge density may promote epizootic transmission among wildlife hosts, expansion of urban land use at forest frontiers increases spillover risk. In the Amazon, ongoing forest fragmentation and urban encroachment are raising the likelihood of YFV transmission to people.

Effective waste management is fundamental to the success of social living, playing a key role in disease prevention and maintaining a habitable environment. However, experimental evidence for its adaptive significance remains limited, primarily due to the difficulties in manipulating defaecation behaviour. The social spider mite Stigmaeopsis longus defaecates cooperatively near nest entrances, guided by tactile and chemical cues. We experimentally altered the number and location of defaecation sites using host plant extracts that mimic the chemical cues and examined the effects on reproduction and survival under different female densities. Centralized and increased defaecation sites reduced egg survival in high-density nests, but not in moderate-density ones. Nevertheless, both densities exhibited increased nest extension, suggesting a compensatory response. When nest extension was physically prevented, egg survival declined even in moderate-density nests, confirming that nest extension mitigates the faecal hazards. These findings demonstrate that spatial control of waste is crucial for supporting group living by reducing exposure to faecal hazards, particularly for immobile life stages such as eggs. This study provides the first empirical evidence for the adaptive function of waste management in spider mites, highlighting its potential role in the evolution of sociality and nest-based living in arthropods.

Syngameons consist of a group of species interconnected by repeated cycles of gene flow, where interbreeding can lead to fertile hybrid offspring capable of backcrossing with the parental species, facilitating the introgression of genomic regions among species. These networks have been known for over a century in plants, although mainly documented in temperate tree species. Emerging evidence from phylogenomic studies strongly suggests the existence of syngameons in tropical rainforest trees, challenging the traditional view that tree species hybridization is rare in these tropical ecosystems. Several biological characteristics of tropical trees, such as high number of co-occurring species in tropical ecosystems, generalist pollination strategies and predominantly outcrossing, could favour the evolution of syngameons. Here, we review the most recent approaches to distinguish the signal of hybridization from other evolutionary processes. We emphasize the need for robust methodologies to detect hybridization and introgression, advocating for an integrative framework combining phylogenomic, phylogeographic and population genomics analyses that will allow us to confirm the presence of syngameons in tropical trees. We argue that syngameons in tropical ecosystems may play a significant role in the distribution and maintenance of species diversity and discuss that a more integral approach of conservation is required to safeguard the integrity of these networks.

The ability to process temporal information is crucial for animal activities like foraging, mating and predator avoidance. While circadian rhythms have been extensively studied, there is limited knowledge regarding how insects process durations in the range of seconds and sub-seconds. We aimed to assess bumblebees' (Bombus terrestris) ability to differentiate the durations of flashing lights in a free-foraging task. Bees were trained to associate either the long- or short-duration stimulus with a sugar reward versus an unpalatable solution until reaching a criterion and then tested without sucrose solution with the same stimuli. In experiment 1, we tested the ability to discriminate between a long stimulus (2.5 or 5 s) versus a short stimulus (0.5 or 1 s). The bees learned to discriminate between the two stimuli. To check whether bees solved the task without using the absolute difference in proximal stimulation as a cue, we ran a second experiment. In experiment 2, the flashing stimuli were presented for the same total amount of time in a cycle. Bees could discriminate between durations when the amount of stimulation in each presentation cycle was the same. This shows general learning abilities in bumblebees, that can discriminate second/sub-second intervals in visual flashing stimuli.

Understanding the environmental drivers of host-parasite interactions is a major concern to human health and conservation, particularly in the context of emerging infectious diseases. The likelihood of contracting an infection can be related to both the rate of contact between host and parasite, as well as innate features of hosts (susceptibility/resistance) and parasites (infectivity, virulence, within-host proliferation rate). This study uses a host-parasite system with a matching-allele model for host susceptibility and parasite infectivity to disentangle contact rate from parasite infectivity while accounting for the effects of host susceptibility. Using three exposure doses from several parasite isolates to hosts with known susceptibility, we find significant differences in parasite infectivity (in terms of number of successful infections) and within-host proliferation rate among parasite isolates, after controlling for exposure rate and host genotype. Host known susceptibility also had a strong impact on parasite infection success and proliferation rate, due to the nature of this host-parasite system. The exposure dose did not impact the number of infections or infection intensity. No significant relationship between infection success and parasite proliferation rate was detected, indicating a weak or non-existent covariance among isolates for both variables.

Due to ongoing global urbanization, some animals have settled in urban environments and rely increasingly on anthropogenic resources. One such urban adapter is the European herring gull, Larus argentatus, whose presence in towns has led to conflict with humans. Previous research has found gulls perceive men's shouting as a threat. We conducted a playback experiment on wild urban herring gulls in a foraging context to determine whether gulls perceive the difference between men shouting versus speaking the same words at the same volume, and whether those stimuli represented the same level of threat. Gulls reacted similarly to men shouting and speaking, as they flinched at the playback, exhibited vigilance, pecked less at the human food source and left the apparatus sooner than when exposed to robin song. However, gulls differentiated between the acoustic properties of men's vocalizations, as they flew away from men shouting but walked away from men speaking. When attempting to deter gulls from exploiting anthropogenic resources, talking might stop them from foraging, but shouting is more effective at making them flee.