Oecologia最新文献

Despite the prevalence of both Harmonia axyridis and its fungal ectoparasite Hesperomyces harmoniae across the globe, few studies have explored the impact of Hesperomyces harmoniae on the immune system and thermal performance of Harmonia axyridis, both of which are important traits for the continued geographic range expansion of this invasive species. Since He. harmoniae does impose a cost on Ha. axyridis (overwintering survival), we predicted that infected ladybirds collected from the field would have an increased immune response and decreased phenotypic performance compared to uninfected ladybirds. Moreover, these effects would depend on the season in which ladybirds were collected (summer growing vs autumn pre-overwintering season). In general, collection season had a significant effect on all physiological traits we assayed. All hemolymph parameters significantly decreased from summer to autumn. Ladybird movement activity and range of utilized temperatures increased from summer to autumn, whereas, average preferred temperature decreased from summer to autumn. Unsurprisingly, summer ladybirds were more heat tolerant and autumn ladybirds were more cold tolerant. He. harmoniae infection had almost no impact on any of the investigated traits. The only exception to this was with respect to cold tolerance, He. harmoniae infected ladybirds being less cold tolerant than uninfected ladybirds. Therefore, infection by this fungus does not appear to be physiologically severe enough to elicit a whole-body negative effect on its host ladybird, but instead, may deplete specific internal resources that negatively impact cold tolerance.

Dispersal is a key adaptive strategy to escape deteriorating environments, and habitat selection by dispersers is critical to their own and offspring fitness. Using the haplodiploid spider mite Tetranychus ludeni Zacher as a model species, we investigated how host plant quality influenced dispersal probability, habitat selection, and subsequent reproductive performances. We tested two dispersal scenarios: mated females had triple choice, i.e. residing in low-quality (LQ) or high-quality (HQ) habitat or dispersing to a LQ or HQ habitat. Results show that significantly more females dispersed from LQ habitats than from HQ habitats, and dispersers preferred to settle in HQ habitats regardless of the dispersal scenarios. However, aggregating in HQ habitats resulted in a higher number of eggs accumulated but increased immature mortality which induced restraint of the per capita fecundity. Females dispersed from LQ habitats produced significantly smaller eggs but maintained a similar proportion of daughters compared to those remaining in LQ habitats, whilst females dispersed from HQ habitats produced eggs of a similar size but a significantly higher proportion of daughters, suggesting that dispersing females might manipulate offspring sex ratio by lowering the fertilisation threshold to fertilise relatively smaller eggs. Increasing female density strongly restrained the per capita fecundity when dispersed from LQ to LQ habitats, but increased egg size and daughter production when residing in HQ habitats. Egg size had no significant effect on egg hatching or immature survival. This study delivers insights into the dispersal and reproductive strategies of a haplodiploid species, highlighting how host quality shapes adaptive responses in challenging environments.

Growth rates often increase with temperature, yet organisms generally grow to larger sizes in colder environments. This pattern, referred to as the Temperature-Size Rule, may be better understood by examining how temperature affects both the supply and demand of energy at different body sizes. In this study, we measured the energetics regulating growth in a marine gastropod, Tegula funebralis, by experimentally measuring feeding and respiration across a broad range of sizes and temperatures. This was paired with field measurements of maximum body sizes from 38 populations spanning 18 degrees of latitude. Our experimental results suggest that temperature can have differential effects on the scaling of feeding and respiration rates with body size. Feeding rate increased with body size but at a decelerating rate (scaling exponent = 0.34) and was only mildly affected by temperature. Respiration exhibited a much stronger increase with temperature and shifted from allometric scaling at low temperatures (scaling exponent near 2/3) toward isometric scaling at high temperatures (exponent closer to 1). Energetic scope for growth is thus highly dependent on temperature and driven by the differential sensitivity of energy supply and demand. Our energetic model did a good job explaining temperature-size relationships for T. funebralis (pseudo R² = 0.28), though predictions could be improved appreciably by invoking additional mechanisms (e.g., latitudinal differences in assimilation efficiency or thermal sensitivity), suggesting avenues for future research. Overall, our results suggest that a clearer understanding of the energetics underlying growth can help explain a major life history gradient.

Supplementary feeding is a widely used conservation strategy to support scavenging species, but the full effects remain poorly understood. In the Baltic Sea region, the recovery of the white-tailed eagle (Haliaeetus albicilla) was assisted by an extensive feeding scheme. We examined whether the individual usage of a feeder was associated with the probability to recruit into the local population. At a feeder in Southwest Finland, food was offered during winter, and visiting individuals were identified based on their unique ring codes. In addition, we identified individuals by genotypes extracted from feathers collected from ringed nestlings and from adult feathers collected from nests between 2003 and 2012 and 2008 and 2023, respectively. By matching nestling and adult genotypes, we infer recruitment and relate it to feeder usage. In addition, we explore sex-specific differences, which could arise due to intra-specific competition due to size differences. Our findings reveal that there was high individual variability in feeder usage and that visitation rate was positively associated with the probability to recruit. Although females spent more time at the feeder, recruitment was irrespective of sex. While for individuals the probability to recruit increased from 13.6% to 43.0%, the population-level increases were small, from 13.6% to 14.7%. We demonstrate that winter feeding had the potential to aid the recovery of the white-tailed eagle in the region, although estimating the full effect of supplementary food for the population would require further analyses. Our study highlights the consequences of supplementary feeding and facilitates more informed management strategies for the conservation of endangered species.

All animals require food to survive, grow, reproduce, and thus optimize fitness in nature. Food availability can profoundly affect demographic parameters such as longevity and fecundity. Here, we compared reproductive parameters in the false widow spider, Steatoda grossa (Araneae, Theridiidae), when the availability and size of prey (the house cricket, Acheta domesticus) were manipulated. Adult mated female spiders that were fed weekly (constant prey treatment) produced more progeny during their lifetime than females fed every 3 weeks (intermittent prey treatment). Furthermore, the monitoring of fecundity schedules showed that over the first 10 egg sacs, the mean number of neonate spiderlings per egg sac was around 40% higher in constantly fed than intermittently fed spiders. Time intervals between egg sac productions were generally higher when prey availability was lower. Some females lost more than 50% of their body mass after the production of the first egg sac, although reproductive investment tended to decrease thereafter. The amount of prey offered to females significantly affected mass gain between reproductive events, but fewer progeny were produced by females per egg sac, as well as cumulatively over the first three egg sacs, when they were only fed small prey. Starved females that had not produced egg sacs in several months exhibited total reproductive recovery when fed. Our results demonstrate the importance of prey attributes on S. grossa reproduction. Furthermore, females invest remarkably large amounts of resources during each reproductive cycle and over the course of a lifetime.

Human activities have increased nitrogen (N) bioavailability broadly, resulting in increased plant productivity and decreased plant species richness globally. However, the determinants of the rates of change and the ultimate plant community composition resulting from N additions remain unclear. Here we synthesize data from six long-term N addition experiments in a tallgrass prairie ecosystem to (1) determine whether plant compositional change with N additions occurs gradually or is an abrupt response, (2) identify short-term (i.e., pulse) environmental drivers that may cause compositional changes, and (3) map the end points of plant communities following a decade or more of N addition. We find that most plant community change occurred gradually over the first several years of chronic N additions, with no evidence that other perturbations (i.e., precipitation, herbivory, fire) catalyzed the change. Rather, we think that the observed pattern reflects the long-lived nature of dominant plant species within this community. Additionally, we find that the final community composition differed across the six experiments we synthesized, seemingly driven by differences in the initial plant community composition. Despite different species coming to dominate the six experiments with N addition, these species shared functional identities as fast-growing, weedy species. The shifts in tallgrass plant community composition observed with increased N availability across the six experiments synthesized here may have consequences for the stability of ecosystem function in a world with altered N bioavailability. Long-term experiments are necessary to capture these responses to N addition, with short-term experiments likely underestimating the community responses to altered N.

Community diversity exhibits partial recovery following the cessation of nitrogen (N) addition, yet the underlying mechanisms remain insufficiently understood. In this study, we examined the short-term responses of plant communities and environmental factors to N cessation in an alpine meadow on the eastern Qinghai-Tibetan Plateau after a decade-long period of N addition. Our study reveals a transient window of opportunity for the resurgence of rare species following N cessation. This recovery of rare species was the primary driver of the observed increase in plant species diversity. During this temporary phase, increased light availability and reduced soil nutrient (nitrogen and phosphorus) levels disrupted historical competitive hierarchies by enhancing the performance of rare species while weakening dominant species. These findings offer novel insights into community reassembly under nutrient enrichment stress and highlight the potential for short-term, targeted interventions to facilitate near-natural restoration, providing valuable guidance for ecosystem management and biodiversity conservation in grassland ecosystems.

Ecological stoichiometry can help clarify how symbionts and other co-occurring organisms mediate nutrient deficiencies for hosts. We used ecological stoichiometry (comparisons of elemental compositions in food vs consumer) to investigate whether obligate mutualist fungi (Grosmannia clavigera, Ophiostoma montium) of the tree-killing bark beetle Dendroctonus ponderosae (mountain pine beetle) and the invasive tree pathogenic fungus, Cronartium ribicola (causal agent of the disease white pine blister rust) influenced availability of carbon, nitrogen, and phosphorus to the beetle in Pinus albicaulis (whitebark pine), as well as how these elements varied among three populations of the tree. Nitrogen was 33% higher when phloem was colonized by the mutualist fungi, but phosphorus did not differ. In contrast to the mutualist fungi, infection of trees by the blister rust pathogen was not correlated with changes in carbon, nitrogen, or phosphorus. The contents of these elements were relatively homogeneous in living whitebark pine across populations. Our results indicate that blister rust disease does not shift phloem nutrients in ways that make trees more suitable for bark beetle colonization. However, nitrogen enhancement of beetle diets by fungal mutualists could help support the high colonization densities needed for the mass attacks required to kill trees.

Spatial ecology of species is determined by the interplay of various social and demographic factors. Variation in utilisation of space may also reduce the conflict between individuals competing for the same resources. We simultaneously evaluated the effects of sex, territoriality and reproductive performance on the space use of the Eurasian goshawk, Accipiter gentilis, by analysing the home range sizes of 25 individuals across various stages of the annual cycle for up to 7 years. The mean annual home range (90% autocorrelated kernel density estimate) of territorial goshawks was slightly smaller than that of non-territorial hawks, and the ranges of successful birds tended to be smaller than those of non-successful territorial goshawks. The median home range of territorial females (295 km²) was five times larger than that of males (58 km²). While the home ranges of males overlapped by 89-100% with those of females, only 7-14% of females' ranges were utilised by their male counterparts. The home ranges of territorial females gradually increased after the incubation stage, and their fidelity to nest sites weakened. Males maintained their association with their nest sites throughout the year. These sex-specific differences may be attributed to distinct strategies, with males acting as territory holders and females exploring potential mates and nest sites, or to the reduction of competition between partners. The findings underscore the significance of long-term tracking across annual cycles in determining annual home ranges and show how complex space use patterns are in sedentary dietary specialists under seasonally varying food resources and intra- and extrapair competition.