Journal of Animal Ecology最新文献

Divorce-terminating a pair bond whilst both members are alive-is a mating strategy observed in many socially monogamous species often linked to poor reproductive success. As environmental factors directly affect individual condition and reproductive performance, they can indirectly influence divorce. Given current climate change, understanding how environmental fluctuations affect partnership stability has important implications, including for conservation. Yet, the relationship between the environment and divorce remains largely unstudied. We examined the influence of temporal environmental variability on the prevalence of within- and between-season divorce and the possible underlying mechanisms in a socially monogamous passerine. Analysing 16 years of data from a longitudinal dataset, we investigated the relationship between rainfall and divorce in the Seychelles warbler (Acrocephalus sechellensis). First, we performed climate window analyses to identify the temporal windows of rainfall that best predict reproductive success and divorce. Then, we tested the effects of these temporal windows of rainfall on reproductive success and divorce and the influence of reproductive success on divorce whilst controlling for covariates. Annual divorce rates varied from 1% to 16%. The probability of divorce was significantly associated with the quadratic effect of 7 months of total rainfall before and during the breeding season, with divorce increasing in years with low and high rainfall. This quadratic relationship was driven by a heavy rainfall event in 1997, as excluding 1997 from our analyses left a significant negative linear relationship between rainfall and divorce. Although the same temporal window of rainfall predicting divorce significantly influenced reproductive success, we found no significant correlation between reproductive success and divorce. Our findings suggest that rainfall impacts divorce. Given that this effect is likely not directly mediated by reproductive success, we discuss other possible drivers. Although the 1997 super El Niño event shows how heavy rainfall may affect socially monogamous partnerships, more data are required to estimate the robustness of this effect. By adding to the growing body of literature showing that environmental conditions influence the stability of socially monogamous partnerships, we provide novel insights that may also be important for conservation efforts in times of climate change.

Understanding the diversity and causes of senescence patterns in the wild remains a challenging task, in particular among fast-living species for which senescence patterns have been poorly studied. Early life environmental conditions can shape senescence by influencing trade-offs between early and late life performance (disposable soma theory) or individual fitness through lifelong positive effects (silver spoon effects). Using a 23-year-long monitoring dataset of two populations of Siberian flying squirrels (Pteromys volans L.) in western Finland, we analysed the occurrence, onset and rate of senescence in female survival, body mass and reproductive performance. We also examined how early life pulsed resources (tree masting during the year of birth) influence age-specific variations in these traits. Our results indicate that survival senescence occurs after sexual maturity from 3 years of age. Females experiencing high resource availability at birth tended to survive better, but the age-specific trend was not affected by early life resource conditions. Maternal body mass declined slightly with age, starting at 4 years, regardless of early resource conditions. Similarly, among reproductive traits, we showed late-onset senescence in both litter size and annual reproductive probability, with no evidence supporting an effect of early life resources on these trends. We found no decline in juvenile body mass or in the juvenile size-number trade-off with maternal age. Our findings suggest that pulsed resources experienced at birth have a limited long-lasting impact on the life-history traits of this fast-living rodent, with no significant effect on senescence patterns.

1. Differential vulnerability to heatwaves may affect community dynamics in a changing climate. In temperate regions, this vulnerability to heatwaves depends on the interactions between seasonal temperature fluctuations and the capacity to rapidly shift thermal performance curves. 2. Here we investigate how these dynamics affect the vulnerability of two ecologically important copepod congeners, Acartia tonsa and A. hudsonica, to heatwaves of different durations. Using a combination of field observations and simulated laboratory heatwave experiments, we uncover strong seasonal variation in the performance curves of A. tonsa but not A. hudsonica. This translated to species-specific seasonal patterns of vulnerability to heatwaves, with increased vulnerability in A. hudsonica. 3. By reducing parental stress during simulated heatwaves, seasonal performance curve shifts likely reduced indirect, transgenerational effects of these events on offspring performance in A. tonsa. 4. Our results illustrate how different levels of seasonal variation in thermal performance curves will affect population persistence in a changing climate.

North American bird abundance has declined by 29% over the last 50 years. These continental population dynamics interact with local landscape changes to affect local bird diversity. Mitigating local declines in cities is particularly significant because (a) such declines greatly impact human-bird relationships since most people live in cities and (b) cities provide levers to create bird-friendly habitat, such as managing yards and gardens, street trees, and urban parks. Yet, the potential for cities to modify habitats to mitigate broader bird declines remains unclear. Studies have been stymied by the difficulty of assembling mutidecadal habitat-bird population datasets. Instead, studies have substituted space for time (e.g. used habitat associations across space at one time point to project future species abundance due to changing land use), but this method may fail amidst nonstationary environments of the Anthropocene. Here, we test the validity of space-for-time substitutions for explaining changes in bird abundance in a North American city over the past two decades by examining the degree to which these changes are explainable by changes in local landcover at multiple spatial scales. Specifically, we use longitudinal urban bird surveys of Metro Vancouver, BC, Canada from 1997 and 2020; deep learning models of remote sensing data to classify contemporaneous landcover; out-of-sample prediction and boosted regression trees to identify multiple spatial scales of landcover that best explained bird abundance (i.e. optimal scale of effect for each species by each habitat); and Bayesian multispecies abundance models in Stan to determine relationships between changes in landcover and bird abundance. We found that total bird abundance declined by 26% over the last two decades. Landcover measured at both 50 m and optimal scales explained spatial variation in bird abundance, but only landcover at the optimal scale explained temporal changes, and only partially. These results suggest that space-for-time substitutions overemphasize habitat-bird ecological relationships, urban habitats only partially determine bird abundance, and measuring habitat at the appropriate scale is important for capturing the most relevant changes in landscapes.

Behavioural variation among individuals is a hallmark of cooperative societies, which commonly contain breeders and non-breeders, helpers and non-helpers. In some cases, labour is divided with non-breeders "helping." Conversely, in some societies, subordinate non-breeders may not help. These individuals may be (i) an insurance workforce ensuring continuity of help for breeders when other helpers are lost, (ii) conserving energy while waiting to breed themselves or (iii) simply of too poor physiological quality either to help or breed. In the Australian Outback, Acacia thrips Dunatothrips aneurae (Thysanoptera) glue Acacia phyllodes into "domiciles" using silk-like secretions, either alone or cooperatively. Domicile maintenance is important for humidity, so repair can be interpreted as helping. I found that not all females helped to repair damage; some repaired partially or not at all ("non-helpers"). At the same time, some co-foundresses are non- or partially reproductive ("non-breeders"), and their role is currently unknown. I first tested the possibility that helping and breeding are divided, with non-helping females breeding, and non-breeders helping. In a lab experiment, I rejected this idea. Experimentally damaged domiciles were typically repaired by reproductive females, and less so by non- or partially reproductive individuals. To test whether non-helpers are an insurance workforce, I successively removed repairing females and found that non-helping females from the same domicile did not increase effort as a result, rejecting this hypothesis. Then I tested whether non-helpers were conserving energy waiting to breed. In a field experiment, I removed all other females, allowing either a helpful female or a non-helper to "inherit" her domicile. Isolated like this, non-helpers laid very few eggs compared to helpers or naturally occurring single foundresses, despite similar ovarian development. My findings show that labour was not divided: reproduction and helping covaried positively, probably depending on individual variation in female quality and intra-domicile competition. Non-helping females were neither an insurance workforce nor conserving energy waiting to breed. They are likely simply of poor quality, freeloading by benefiting from domicile maintenance by others. I hypothesize they are tolerated because of selection for indiscriminate communal brood care in the form of domicile repair.

Animals combine colour change and behavioural choices to enhance concealment and adapt to changes in habitat in time and space. However, non-native and invasive habitat-forming plants and seaweeds can change the landscape, challenging animals to remain camouflaged, especially when the colour of the new habitat differs from the native backgrounds.The chameleon prawn (Hippolyte varians) exhibits remarkable colour variation and effective camouflage against different native seaweeds in shallow tidepools. Individuals optimize crypsis by choosing colour-matching seaweeds and changing colour over time. In some locations, the prawn's native habitats are now replaced by non-native seaweeds of different coloration and structure, making it important to understand whether substrate choice and colour change facilitates the occupation of these seaweeds and enables prawns to camouflage against new backgrounds.Using image analysis and visual modelling of a fish predator, we assessed the colour variation and camouflage of chameleon prawns occupying the non-native seaweeds brown wireweed (Sargassum muticum) and pink harpoon weed (Asparagopsis armata) in southwest UK. We performed laboratory trials to examine whether prawns maintain their preference for colour-matching native substrates when given a choice between them and non-native seaweeds, and if they can change their coloration to improve camouflage against non-native substrates.Prawns exhibit phenotypic diversity and camouflage that varied with the non-native seaweed species, with low colour variation and effective camouflage on pink harpoon weed, but high colour diversity and reduced concealment against brown wireweed. Prawns choose non-native seaweeds when the alternative native substrate provides mismatching coloration, but they did not exhibit any preference between colour-matching native and non-native seaweeds. Once in non-native habitats, prawns change their appearance over a few days to match the background, sometimes faster than when changing on native seaweeds of contrasting coloration.Although human activities considerably modify the coloration of marine landscapes by increasing the establishment of non-native seaweeds, the impacts of those changes appear less severe for colour-changing species, such as chameleon prawns, and will depend on the similarity between the colour of the new substrates and the original native backgrounds, and how animals use behaviour and physiology to match new habitats.

Understanding elevation variation in biodiversity is a classic question in ecology and has implications for understanding climate change impacts on mountain ecosystems. While insects are the largest group of animals, the global trend in insect species richness with elevation is unknown. To date, single studies and taxa-specific syntheses have provided no single picture, finding variable patterns of insect richness with elevation. A global synthesis across systems would provide a better understanding of how insect species richness changes with elevation and the possible environmental correlates of those patterns. We used published studies of terrestrial insect elevation gradients from 1990 to 2020 to ask: How do insect species richness change with elevation, and which environmental variables best explain this relationship statistically? With 1486 sites spanning 151 species richness-elevation gradients from 80 studies from four diverse insect taxonomic groups and five biomes, we found that overall proportional richness reached a low-elevation plateau and then decreased. We also show that mean annual temperature and seasonality best explain this trend. We suggest best practices and areas of interest for the future of insect richness-elevation studies, including underrepresented groups, geographic areas, and more standardized methods.

Research Highlight: Knutie, S., Bahouth, R., Bertone, M., Webb, C., Mehta, M., Nahom, M., Barta, R., Ghai, S., Love, A., Horan, S., Soldo, A., Cochrane, E., Bartholomew, J., Cowan, E., Bjerke, H., Balenger, S., Butler, M., Cornell, A., Kennedy, A., Rolland, V., Schultz, E., Stanback, M., Taff, C., Albery, G. (2024). Understanding spatiotemporal effects of food supplementation on host-parasite interactions using community-based science. Journal of Animal Ecology. https://doi.org/10.1111/1365-2656.14155. Wildlife have become increasingly dependent on anthropogenic food supplementation, resulting in altered nutritional intake and inter- and intraspecific interactions. Subsequently, supplemental feeding can affect both the immunological function of individuals and transmission dynamics among individuals and species. The magnitude of the effect supplemental feeding has on disease is likely to vary across time and space with the nutritional demands of hosts. However, the broad temporal or spatial scale effects of supplementation are poorly understood. Recently, Knutie et al. (2024) introduced their citizen science program, the Nest Parasite Community Project, a broadscale coordinated effort by scientists and the public to monitor box nesting wild birds and their ectoparasites across the eastern United States. The authors amassed an impressive 4-year data set with hundreds of nests spanning the entire US breeding range of Eastern bluebirds (Sialia sialis). In the first study to come from the project, the authors demonstrate that the effects of food supplementation on host-parasite interactions vary across time and space and do not consistently influence host-parasite outcomes, highlighting that host-parasite interactions are often context dependent and influenced by many environmental factors (e.g. weather and habitat quality). The authors also found that supplemental feeding increases host fitness, regardless of parasitism. The study provides strong evidence that citizen science projects can help broaden our understanding of how human food sources influence wildlife disease in various environmental contexts.

Changing drought regimes are a rising threat to biodiversity, yet their impacts on wildlife vary greatly. Acknowledging the factors associated with these consequences brings novel insights into species vulnerability resulting from extreme climatic events and facilitates effective mitigation of climate change risks. Based on 319 observations from 29 peer-reviewed studies on birds-a well-monitored taxonomic group-we extract the responses of demographic metrics to droughts for 204 species across eight terrestrial biomes to examine the consequences of droughts. According to relevant studies, we chose the factors potentially moderating bird demography under droughts and compiled the data for these factors from published datasets. A meta-analysis is performed to determine the drought effect on bird demography at individual and population levels, accounting for the influence of species traits, timescale and severity of droughts, as well as biome features. The results show that droughts have an overall negative effect on bird demography, and the effect is mediated by different factors at each level. For individuals exposed to droughts, declines in demographic rates are found to be related to narrower extents of occurrence of species, and a significant overall reduction in demographic rates is identified for individuals residing in deserts and xeric shrublands. At the population level, declines in abundance or reproductive performance are generally identified for invertivores, frugivores, nectarivores and omnivores; short-lived species with small clutch sizes also show greater susceptibilities under the impacts of droughts. Our findings additionally suggest that the demographic vulnerability of bird individuals and populations could be affected by the duration and magnitude of drought episodes. Although our results are subject to publication bias, these conclusions advance the assessment of vulnerability to extreme climatic events that used to be based on equally weighted species traits and support bird conservation by prioritizing the declining populations of species with drought-susceptible traits.

Living organisms are exposed to multiple environmental factors that can affect their fitness. The negative effects of these simultaneous stressors can be additive or can interact in negative synergistic or antagonistic ways to affect the health of exposed individuals. Parasites can accumulate pollutants in their own tissues and have been shown to increase the tolerance of their hosts to different pollutants (antagonistic interaction between parasites and pollutants). Through an experimental approach, we tested the existence of combined antagonistic effects between intestinal parasites and lead exposure on urban feral pigeons (Columba livia) which are known to be exposed to trace metal pollution and harbour a wide variety of internal and external parasites. We experimentally exposed wild feral pigeons in captivity to two treatments: an anthelmintic treatment to eliminate intestinal nematode parasites; an exposure to lead for a period of 6 months. We tested the effects of these crossed treatments on several components of fitness: immunocompetence, reproduction, and body mass. Our findings suggest that the overall effects of lead exposure, either alone or in combination with the presence of intestinal parasites (without anthelmintic treatment) were negative, through either additive or synergistic means. Our results reveal the existence of negative combined effects between pollutant exposure and intestinal parasites, highlighting the importance of accounting for multiple stress factors when studying the effects of exposure to pollutants and/or other environmental stressors on the fitness of organisms.