Oecologia最新文献

Petiole mechanics is essential for displaying leaf lamina efficiently in a shaded forest understory. We investigated the structure, anatomy, and mechanics of the petioles of 25 coexisting woody species in a warm-temperate forest understory and related them to interspecific differences in leaf size, habit (evergreen vs deciduous leaves), and form (simple vs compound leaves). Flexural stiffness of the petioles was greater in large leaves than in small leaves, in evergreen leaves than in deciduous leaves of similar area, and in compound leaves than in simple leaves of similar area. Greater second-order moment of area of petioles was responsible for greater flexural stiffness for species with large leaves and evergreen species. In contrast, the petioles of compound leaves showed a greater modulus of elasticity, but a smaller second-order moment of area compared to those of simple leaves of similar leaf area. Anatomical properties were related to the flexural stiffness and resulted in different biomass costs of the petioles. These results are consistent with the idea that the petioles of compound leaves are analogous to laterally growing branches, in which the increase in density is theoretically efficient in terms of the mass required to produce a branch of a given length. Therefore, different factors constrained the flexural stiffness of petioles among coexisting species of different leaf groups.

Bees are essential for ecosystem functioning, pollinating many wild and crop plant species. Predicting which species are most vulnerable to global changes, and how their loss may impact ecosystems and human well-being, is critical. Comprehensive information on bee response and effect traits is fundamental to these assessments. However, the Raunkiærian shortfall-insufficient trait data-remains significant for bees, particularly in the Neotropics. Moreover, it remains uncertain whether conservation strategies based on functional diversity from temperate regions can be generalized to the Neotropics. To address this gap, we compiled a comprehensive and validated dataset on Brazilian bee traits, covering 24 traits related to sociality (100% of the species with some information), nesting (88%), body size (71%), and buzzing capacity (42%) on 2,066 Brazilian bee species. The trait data here presented is a crucial resource for evaluating bee species' pollination effectiveness and susceptibility to global change. Comparative analysis with regions with ample trait data-USA, Europe, and China-revealed notable differences. Brazilian bees exhibited a higher prevalence of aboveground nesting species, especially compared to Europe. The proportion of eusocial species was also greater than in Europe and the United States, and more similar to China. Differently from other regions, Brazilian eusocial bees were significantly smaller than their non-eusocial counterparts. These cross-regional comparisons highlight the importance of geographically tailored conservation strategies and underscore the need for extensive trait data to accurately predict regional vulnerabilities and ecological impacts in a rapidly changing world.

Plant biodiversity can influence the structure of other trophic levels, with cascading effects on ecosystem functioning. Biodiversity-ecosystem function (BEF) experiments that manipulate tree diversity provide information on the mechanisms that drive these bottom-up effects. In this study, conducted in a seasonally dry tropical forest BEF experiment in South America, we tested the hypotheses that ground-dwelling arthropod abundance and diversity are positively affected by tree species richness and a gradient of plant facilitation which can potentially increase community productivity, resource heterogeneity, and soil conditions. Using generalised additive models (GAM), we found that tree richness, which directly affects leaf litter heterogeneity, positively affected total arthropod richness, as well as the richness of Hemiptera, Hymenoptera, and predators. Contrary to expectations, facilitation had no detectable effect on the structure of the arthropod community. Nutrient availability and mean tree height, used as a proxy for community productivity, emerged as the main drivers of arthropod abundance. Our results indicate that the effect of tree diversity on ecosystem functioning can be mediated by ground-dwelling arthropods.

Drought and flooding events are becoming increasingly frequent and intense due to climate change. We examined how drought and flooding affect the morphophysiological performance of Eugenia uniflora, focusing on gas exchange, water status and growth traits. E. uniflora's responses to water stress are strongly influenced by previous hydrological conditions. Early drought caused marked declines in plant water status, photosynthesis, and water-use efficiency, while early flooding had negligible effects on morphological and physiological traits, reflecting the species' high flood tolerance. Preconditioning through previous flooding or exposure to a single drought mitigated the negative effects of subsequent stress, allowing partial or full recovery of gas exchange and growth traits, with morphological adjustments stabilizing more rapidly than physiological responses. In contrast, recurrent drought imposed severe constraints on water status, gas exchange, and growth, highlighting the cumulative burden of repeated stress, whereas recurrent flooding elicited moderate physiological declines without affecting growth traits. These results demonstrate that both the type and sequence of water stress shape the resilience of E. uniflora, with morphophysiological plasticity and stress history enabling rapid adjustments to fluctuating hydrological conditions in subtropical riverine forests. This resilience suggests that the species could be valuable for restoring riparian ecosystems facing hydrological extremes.

Omnivores often face tradeoffs between selecting for spatially dispersed energy-dense vertebrate prey versus densely distributed herbivorous resources that have limited energetic value per unit intake. Arctic grizzly bears (Ursus arctos) are large omnivores within a resource-limited ecosystem that are known to exhibit smaller body masses and occur at lower densities than grizzly bears in other regions of North America. We evaluated the energy balance of Arctic grizzly bears during a portion of the fall hyperphagic period in two ecologically differing regions on Alaska's northern Arctic coast by monitoring mass change, food intake, activity, and energy expenditure of 12 individuals over 17-22 days. Bears in coastal areas were more carnivorous than bears in the foothills that were predominantly herbivorous and frugivorous. Carnivory was associated with greater movement, body fat, and energy expenditure and two of four carnivorous bears lost mass. Overall, the mean body fat of the bears in this study was 34% lower than other grizzly bear populations in North America in the fall. Furthermore, the bears in this study exhibited relatively small changes in body mass ( $\overline{x}$  = 3%, range =-2 to 11%) that were 60% lower than other grizzly bear populations which typically gain substantial mass in the fall in preparation for denning. Our results, while representing a snapshot from a small number of bears during the fall hyperphagic period, are consistent with previous studies and indicate limited availability of energy-dense food resources during this time for grizzly bears in this region of the Arctic.

While plant defense against herbivory is primarily thought to occur following attack, there is also evidence that plants can detect and respond to pre-attack cues. These cues include chemicals released from damaged conspecifics and kairomones, non-attack-related substances emitted by an herbivore that plants can detect and use to their benefit. It is unknown, however, whether or how plants react to the interaction of these pre-attack cues. We measured germination, growth, and herbivore susceptibility of B. nigra seedlings in an experiment that crossed the presence/absence of crushed B. nigra leaves with the presence/absence of mucus of a generalist herbivore, A. subfuscus. Seeds exposed to both crushed leaves and slug mucus germinated 8% more quickly than control seeds; neither risk cue increased germination speed when tested individually. The same pattern was found in herbivore bioassays: Spodoptera exigua ate almost 10 × more foliage from control seedlings than from seedlings exposed to both crushed leaves and slug mucus. There was no difference in the final biomass of mature plants, suggesting that plants exposed to herbivore cues early in their development can increase defense without a measurable cost in size at maturity.

A complete understanding of factors that influence animal fitness requires that we measure not only those occurring day to day in the life of an animal but also those that operate on longer time scales. Here, we investigated silver spoon effects (fitness impacts resulting from conditions faced early in life) and carryover effects (fitness impacts caused by environmental factors in a previous season) in a northern Wisconsin population of the common loon (Gavia immer). The mass of a loon chick divided by its age, an indication of food it received from its parents in its first 4 to 6 weeks of life ("chick condition"), affected both the likelihood of survival to adulthood and, among territory settlers, the number of chicks it fledged as an adult. Only one carryover effect was evident: increased ocean pH on the wintering ground had a modest positive effect on territory settlement rate. However, cohorts of loons that faced unfavorable ocean conditions in their first year yielded adults that fledged many chicks, which suggests that selection resulting from poor ocean conditions removed weaker phenotypes. The robust silver spoon effect in this species helps us understand a current and alarming pattern in the Wisconsin loon population: the sharp decline in the survival of chicks to breeding age.

Chemical defense mechanisms in certain plant seeds yield secondary metabolites that can adversely affect rodents. In forest ecosystems, acorns high in ellagitannins (ET) serve as a significant nutrient source for rodents; however, the long-term impacts of ingesting tannin-rich acorns on reproductive organs and overall reproduction remain unclear. In this study, four types of artificial seeds with different ET contents (0, 2, 7, and 12%) were fabricated to simulate various acorn types. We investigated the effects of ET on the survival and reproduction of Kunming mice (Mus musculus). Results revealed that increasing ET content significantly inhibited weight gain and reduced survival rates, with male mice being particularly sensitive. High ET levels were associated with alterations in the physiological structure of the ovaries and testes, premature aging, and other deleterious effects, which may impair sperm quality in males and compromise fertility in females. Furthermore, a medium ET content inhibited an increase in embryonic body length, disrupted the structural and functional integrity of embryos, and reduced the number of blood cells in the labyrinth layer of the placenta. These findings suggest that tannins in Quercus seeds may affect rodents' growth and reproduction, thereby potentially playing a regulatory role in rodent population dynamics.

Increased variability in precipitation associated with climate change creates extreme conditions of drought and deluge that can have profound effects on the abundance and composition of plant communities. Responses to these extremes likely vary across climatic gradients and depend on local plant community composition, which includes the emergent, aboveground vegetation as well as belowground seed banks. Because seed banks can both buffer the effects of environmental change and influence the future trajectories of communities, it is critical to understand seed bank responses to precipitation extremes in relation to the aboveground vegetation and how patterns vary across environmental gradients. Here we quantified the responses of aboveground and seed bank communities at five perennial grass-dominated sites across an elevational gradient to 6 years of extreme drought and deluge, by implementing experimental water exclusion and water addition treatments. Responses were stronger for drought than for deluge. Drought decreased abundance aboveground, while seed bank abundances were generally unaffected. Similarly, drought decreased richness and diversity of aboveground vegetation at intermediate elevations, without concurrent changes in seed banks. Surprisingly, the lowest and middle elevation sites showed stronger shifts in functional composition and dissimilarity in response to treatments, despite the expectation of greater buffering in seed banks in more arid environments. The relatively attenuated responses of seed bank communities to drought and deluge suggest potential for resistance and recovery, though species and functional composition may show greater responses to change particularly in more arid, lower elevation sites.

Torpor is an important energy-saving strategy for small insectivorous bats during winter. White-nose syndrome (WNS), a fungal disease affecting hibernating bats, disrupts torpor-arousal patterns and increases energy use, leading to higher winter mortality. In North America, WNS has also infected bats in milder southern climates, supporting concerns about potential impacts if introduced to the Southern Hemisphere. To understand the winter hibernation ecology and sensitivity to WNS of cave-roosting bats, we used temperature telemetry to study torpor patterns and body mass change of the eastern bent-winged bat (Miniopterus orianae oceanensis) at a cold and warm site (mean annual surface temperature 11.7 and 17.8 °C, respectively) in southeastern Australia during winter. Torpor bouts were 4.6 times longer at the cold site (30.8 ± 21.4 h, max = 304.8 h) than at the warm site (6.7 ± 3.8 h, max = 46.5 h), and normothermia duration was longer at the warm site (7.8 ± 3.6 h) than at the cold site (6.6 ± 2.9 h). Torpor bout duration, probability of arousal, and normothermia duration were influenced by nightly weather and season. Mean overwinter body mass loss was twice as high at the cold site (3.1 g) than at the warm site (1.2 g), likely reflecting overwinter food availability. This study provides insights into bat hibernation in mild climates where WNS poses a threat, suggesting that similarities in overwinter torpor and body mass loss to North American species in similar climates may indicate a risk of reduced winter survival for some Australian cave-roosting bat species.