Journal of Animal Ecology最新文献

Rodents are known to interact with seed plants in three different ways, including predation in situ, scatter hoarding and larder hoarding of seeds. These behaviours span a spectrum from mutualistic seed dispersal to predation, and they are related to species' and environmental characteristics. We used interaction networks to evaluate the structure and drivers of rodent-seed plant interactions, including geography, phylogeny and traits at continental scales. We constructed five aggregated networks, each representing a continent and containing three subnetworks defined by foraging behaviours, tested questions about their network structures and analysed the driving signals shaping rodent-seed plant interactions at network and species levels. Rodent-seed plant networks varied across continents. We found most rodents exhibited a significant propensity for one foraging behaviour and detected significant modular structures in both aggregated networks and subnetworks. We detected significant co-phylogenetic signals between rodents and seed plants. Distance matrix-based regressions on interaction and module dissimilarity of rodents suggest geographical and phylogenetic forces are important in the assembly of rodent-seed plant networks. In addition, multiple species traits correlated with the roles of rodents within aggregated networks; however, the specific traits associated with these roles varied among interaction types. Our results highlight that geography and phylogenetics are dominant in structuring the architecture of rodent-seed plant networks at continental scales and reveal challenges regarding spatial and taxa coverage in rodent-seed plant interactions.

Predicting the strength and direction of sexual selection is a challenge, as the effects of ecological factors, social environment and behavioural plasticity all need to be considered. The operational sex ratio (OSR) is a key variable, which has been shown to (i) affect the strength and direction of mating competition, as a social environment cue, and (ii) be affected itself by ecological conditions through sex-specific environmental effects. Gaining a global view of (i) and (ii) in wild populations represents a necessary step for our understanding of sexual selection dynamics in the wild. Here, we address this challenge within the reaction norm framework. We conducted an extensive field study on the two-spotted goby Pomatoschistus flavescens, monitoring six populations along a latitudinal gradient during an entire breeding season. We compared the temporal trajectories in social environment and sexual displays across populations, which is unprecedented. Using a reaction norm framework based on OSR theory, we show that what appears to be great variation in sexual displays across populations and sampling times, follows consistent rules. Sexual display behaviour followed behavioural reaction norms in response to the social environment that were consistent across populations, but social environment fluctuations were specific to each population. Recording behaviour not only over time, but also along a latitudinal gradient where ecological conditions vary and in turn affect OSR, was necessary to reveal the relationship between social environment and sexual displays, which in turn contributes to sexual selection dynamics.

While biodiversity loss is undeniably a global phenomenon, an increase in taxonomic richness has recently been reported from some ecosystems and spatial scales. A striking increase in abundance and/or species richness has been documented from temperate rivers over the last 25 years, with many of the expanding species (i.e. winners) being native species. However, the lack of repeatedly collected local environmental data prevents the exploration of their niche dynamics and also makes it difficult to distinguish between possible causes. We fill this gap by using species occurrence data from 65 pristine Czech rivers sampled in 1997-2000 and 2015. The same methods were used for sampling macroinvertebrates and measuring environmental parameters in both periods. We selected 43 winners, defined as taxonomically validated and originally non-rare native macroinvertebrate species whose occupancy increased by at least six sites between the time periods. We searched for consistent patterns of niche dynamics (i.e. stability, expansion and restriction) among species that might contribute most to the overall increase in species richness. Using several biological traits, we also compared the winners with the other 253 taxa collected to look for differences. Analysis of the occurrence data showed that niche stability was by far the predominant pattern of the niche dynamics. This clearly indicates that the winners fill their original niches, with a limited contribution of niche shift or expansion, depending on the species. As no significant differences in either temperature preferences or the other biological traits were found between the winners and the other taxa, there is no unique set of functional traits that explain the success of the winners. The observed mechanism of filling the original niche space by the spreading native species not only explains the increase in local species richness, but also contributes to support the hypothesis of a climate-driven increase in ecosystem energy flow from a new perspective. The increased metabolism of the system may relax interspecific competition allowing it to carry more individuals and species, even without the need for an increase in nutrients and ecosystem recovery.

Phenological changes have been widely documented in animal and plant responses to directional environmental change. However, predicting the consequences of these shifts for species interactions and population viability requires knowledge of vital rate responses to biotic and abiotic drivers. Here, we paired long-term phenology data documenting monarch butterfly abundance and occurrence of their milkweed hostplant with outdoor experiments in the central United States to ask how changes in spring arrival times to monarch breeding sites affect their development, survival, and within-season population growth. Monarch arrival times did not change across the 17 years of monitoring, but the peak abundance of monarchs, which occurred just prior to their fall migration, shifted 9 days later in 2019 as compared to 2003. Summer population growth declined from 2003 to 2019, significant in ~80% bootstrap calculations. Phenological changes in milkweed occurrence mirrored changes in monarch abundance, happening later through time. Our field experiment showed that early season larval survival was highest when the timing of hatching matched the average timing of the first natural monarch cohort; survival was lowest when egg hatching shifted 14 days earlier. The results of our study indicate that earlier arrival of adult monarchs to summer breeding habitat would be costly for monarchs-but field survey data show that arrival times have not changed to date. Instead, the local changes we observed in the timing of peak abundance occurred towards the end of the breeding season, not the onset. At present, we conclude that changes in early season phenology are not a threat to eastern North American monarchs living in the central United States, but drivers of breeding-season growth rates and changes in late-season phenology merit further study, both in the central United States and in other parts of the monarch's range.

Human activities have converted mature forests into mosaics of successional vegetation and chronically disturbed habitats, altering the patterns of population distribution, foraging ecology and thus, the flow of matter and nutrients through ecosystems. Although the effects of human disturbance are mostly harmful, hyperabundant native generalist species can emerge and increase their populations under disturbance, such as leaf-cutting ants (LCA), prominent herbivores that are considered ecosystem engineers. Here, we examined the population response of two LCA species of the Caatinga dry forest (Acromyrmex balzani and A. rugosus) to increasing levels of chronic anthropogenic disturbance and aridity, and assessed the foraging activity, biomass and nutrients harvested by their colonies. We found that colony densities increased at more disturbed habitats, varying considerably from 0 to 81 nests/ha, but aridity had no effect. The two species exhibited markedly different foraging activities (44.66 ± 28.76 and 294.6 ± 260.53 ants foraging daily), with the foraging rate increasing in more arid conditions for a species with smaller nests, but with no response to disturbance. Biomass consumption varied distinctly between species, ranging from 0 to 4.81 g (7.24 kg ha.year^-1, in A. balzani) and from 5.6 to 74 g (174.39 kg ha.year^-1, in A. rugosus). Furthermore, there was no effect of disturbance and aridity on the biomass harvesting of individual colonies. However, there was a considerable increase in the biomass harvested by the populations of colonies in the plots (i.e. accounting for colony densities). Moreover, the species A. balzani foraged upon more nutrient-rich material at more disturbed and arid habitats, with plant material containing higher concentrations of N, Ca, S, Sr, Fe and Mn, as well as a lower C:N ratio in these areas. Our results suggest that Acromyrmex species (1) can achieve larger populations in more disturbed habitats, though not directly associated with aridity, (2) operate as a key herbivore able to fit harvesting/diet through the entire environmental gradient and forage complementarily (monocot vs. dicot) and (3) reallocate expressive amount of forest biomass, resulting in temporary nutrient sinks with potential impacts on Caatinga resilience.

Infection imposes energetic costs on hosts. Hosts typically respond by shifting resources, potentially affecting the quantity and quality of offspring they produce. As the sexes differ in their optimal reproductive strategies, the infection of mothers versus fathers may affect offspring quantity and quality in different ways. Here, we test how experimental infection of guppies Poecilia reticulata with the ectoparasite Gyrodactylus turnbulli affects parental reproductive fitness and offspring parasite resistance. We compared breeding pairs in which one or neither parent had previously been infected. In terms of reproductive fitness, pairs in which fathers had been infected produced more offspring than those in which mothers had been infected. Additionally, fathers who experienced the heaviest infections produced offspring ~55 days sooner than average. This result may represent terminal investment by males, especially those most affected by infection, or that males invest in reproduction at the expense of parasite defence. We found that offspring age, parental infection experience, and parental infection severity together strongly predicted offspring parasite resistance. Only among pairs in which one parent had been infected did older offspring, which were those born soonest after the parent's infection, tend to experience heavier infections. This result may reflect temporary infection-induced reductions in parental investment in offspring quality. Beyond this effect of offspring age, offspring of infected mothers experienced 105 fewer worm days than those of infected fathers: fathers, but not mothers, who experienced heavy infections themselves produced offspring that also experienced heavy infections. The parent-offspring regression for infected fathers is consistent with previous evidence that parasite resistance is heritable in this system and yields a narrow sense heritability estimate of 0.62 ± 0.12. By contrast, the mother-offspring regression (slope: -0.12 ± 0.14) provides novel insight that mothers may engage in transgenerational immune priming. Our results suggest that the sexes strike a different balance between offspring quantity and quality when faced with infection, with potentially broad implications for disease and host-parasite co-evolutionary dynamics in nature.

There is a vast and ever-accumulating amount of behavioural data on individually recognised animals, an incredible resource to shed light on the ecological and evolutionary drivers of variation in animal behaviour. Yet, the full potential of such data lies in comparative research across taxa with distinct life histories and ecologies. Substantial challenges impede systematic comparisons, one of which is the lack of persistent, accessible and standardised databases. Big-team approaches to building standardised databases offer a solution to facilitating reliable cross-species comparisons. By sharing both data and expertise among researchers, these approaches ensure that valuable data, which might otherwise go unused, become easier to discover, repurpose and synthesise. Additionally, such large-scale collaborations promote a culture of sharing within the research community, incentivising researchers to contribute their data by ensuring their interests are considered through clear sharing guidelines. Active communication with the data contributors during the standardisation process also helps avoid misinterpretation of the data, ultimately improving the reliability of comparative databases. Here, we introduce MacaqueNet, a global collaboration of over 100 researchers (https://macaquenet.github.io/) aimed at unlocking the wealth of cross-species data for research on macaque social behaviour. The MacaqueNet database encompasses data from 1981 to the present on 61 populations across 14 species and is the first publicly searchable and standardised database on affiliative and agonistic animal social behaviour. We describe the establishment of MacaqueNet, from the steps we took to start a large-scale collective, to the creation of a cross-species collaborative database and the implementation of data entry and retrieval protocols. We share MacaqueNet's component resources: an R package for data standardisation, website code, the relational database structure, a glossary and data sharing terms of use. With all these components openly accessible, MacaqueNet can act as a fully replicable template for future endeavours establishing large-scale collaborative comparative databases.

Predator-prey interactions underpin ecological dynamics from population to ecosystem scales, affecting population growth and influencing community stability. One of the classic methods to study these relationships is the functional response (FR) approach, measuring resource use across resource densities. Global warming is known to strongly mediate consumer-resource interactions, but the relevance of prey and predator densities remains largely unknown. Elevated temperature could increase consumer energy expenditure, which needs to be compensated by greater foraging activity. However, such greater activity may concurrently result in a higher encounter rate with other consumers, which potentially affects their total pressure on resource populations because of synergistic or antagonistic effects among multiple predators. We performed a laboratory experiment using three densities of a fish predator (pumpkinseed, Lepomis gibbosus) (one, two and four specimens), two temperatures (25 and 28°C) and six prey densities. Using the FR approach, we investigated the combined effects of elevated temperature and predator and prey density on the consumer's foraging efficiency. We observed a reduced maximum feeding rate at the higher temperature for single predators. However, the foraging efficiency of predators in groups was negatively affected by antagonistic interactions between individuals and further mediated by the temperature. Specifically, we observed a general decrease in antagonistic interactions at elevated compared to the ambient water temperature for multiple predator groupings. Irrespective of temperature, antagonistic multiple predator effects increased with predator density and peaked unimodally at intermediate prey densities, indicating multiple dimensions of density-dependence that interact to supersede the effects of warming. This study shows that conspecific presence negatively affects the per capita performance of predators, but that this effect is dampened with increasing temperature. Their adaptive response to temperature consists of limited food intake and further reduced intraspecific interactions. Including intraspecific competition in study design may thus offer more realistic outcomes compared to widely used experiments with only single predator individuals, which could overestimate the effect of increasing temperature.

Water is an essential and often limiting resource that pervades all aspects of animal ecology. Yet, water economics are grossly understudied relative to foraging and predation, leaving ecologists ill-equipped to predict how the intensifying disruption of hydrological regimes worldwide will impact communities. For savanna herbivores, reliance on surface water can increase exposure to predators and competitors, and thus strategies that reduce the need to drink are advantageous. Yet, the extent to which increasing dietary water intake while decreasing water loss enables animals to forego drinking remains unknown. We studied water budgets of sympatric African savanna antelopes that differ in size, bushbuck (Tragelaphus sylvaticus, ~35 kg) and kudu (T. strepsiceros, ~140 kg). We hypothesized that both species compensate for seasonally declining water availability by increasing consumption of moisture-rich plants and reducing faecal water loss, and that these adjustments are sufficient for small-bodied-but not large-bodied-herbivores to avoid spending more time near permanent water sources as the dry season advances. We tested our predictions using temporally explicit data on antelope movements, diets, plant traits and drinking behaviour in Gorongosa National Park, Mozambique. Water content declined between the early and late dry seasons in roughly half of plant taxa consumed by antelope. Although both species reduced faecal water loss and shifted their diets towards relatively moisture-rich plants as the dry season progressed, dietary water intake still declined. Contrary to expectation, kudu reduced selection for surface water in the late dry season without adjusting total time spent drinking, whereas bushbuck increased selection for surface water. We developed a generalizable approach for parsing the importance of dietary and surface water for large herbivores. Our results underscore that variation in surface-water dependence is a key organizing force in herbivore communities, that simple allometric predictions about the behavioural and ecological consequences of this variation are unreliable. Understanding wildlife water economics is a research frontier that will be essential for predicting changes in species distribution and community composition as temperatures rise and droughts intensify.