Oecologia最新文献

Background matching and disruptive coloration are defense mechanisms of animals against visual predators. Disruptive coloration tends to evolve in microhabitats that are visually heterogeneous, while background matching is favored in microhabitats that are chromatically homogeneous. Controlling for the phylogeny, we explored the evolution of the coloration and the marking patterns in the sexual dichromatic and widely distributed neotropical grasshoppers of the genus Sphenarium. These grasshoppers represent an excellent model to investigate the evolution of cryptic coloration on insects due to the heterogeneity of the environments where they have evolved. We found a correlation between the grasshoppers' coloration and disruptive markings with the chromatic properties of their environments that was inferred by the levels of precipitation during the rainy season. The results suggest that colors and marking patterns could evolve due to predation pressures. Color in both sexes could offer camouflage that is not perfectly background matched to a single habitat but instead offers a degree of resemblance to multiple backgrounds. Moreover, we found that males and females chromatic properties differ between them and precipitation levels where the species are found. This suggests that the sexes have diverged in their response to the environments, favoring the evolution of sexual dichromatism in these grasshoppers.

The effects of climate warming on the distribution of range-expanding species are well documented, but the interactive effects of climate warming and range-expanding species on recipient communities remain understudied. With climate warming, range-expanding species may threaten local biodiversity due to their relatively stronger competitive or predatory effects on potentially weakened, or less well-adapted recipient communities. Acanthinucella spirata is a predatory marine gastropod that has expanded its distribution north along the California coast since the Pleistocene via a poleward range shift, tracking climatic warming. To assess whether A. spirata has stronger predatory effects on the recipient community in their expanded range and is better suited to a warming climate than a local predatory snail, we used a combination of field and laboratory studies to examine the feeding activity of A. spirata and the predatory whelk (Nucella lamellosa) on shared prey under ambient and elevated conditions. From field surveys, we concluded that A. spirata is a potential competitive threat to N. lamellosa, due to its high local abundance, overlapping habitat, and shared prey on Cape Mendocino. In the laboratory, we observed that A. spirata was a more efficient consumer of prey than N. lamellosa overall and ate significantly more prey than N. lamellosa under warmer conditions. As climate change continues, environmental conditions will become more stressful for all species; however, range-expanding A. spirata populations may be at a competitive advantage relative to N. lamellosa, as they are more abundant and have higher feeding rates at warmer temperatures than the local whelk.

Although numerous studies have shown that grazing gives rise to community succession from the communities or even species perspective, there is a lack of discussion about how grazing drives community assembly based on plant functional traits in a long-term experiment. We find different grazing intensities lead to temporal effects on trait-mediated multidimensional community assembly processes, including community-weighted trait mean (CWM), trait filtering, and trait distribution (divergence/convergence). CWM, trait filtering, and trait distribution of different traits transformed over the 16-year grazing experiment. Major findings include the following: (1) CWM changed rapidly under higher grazing intensity, and the removal of unsuitable traits from communities over time was accelerated with higher grazing intensity, such as higher specific leaf area (SLA), rich epidermal appendages (PAP), deep root system (RD), and growth form (shrub and subshrub) and dispersal mode (DM, e.g., insect spread) with higher scores. (2) Patterns of trait filtering strongly depended on grazing intensity and trait types, most traits, such as SLA, DM, PAP, RD, and onset of flowering (OFL), were filtered at high grazing intensity area, and effects of trait filtering in the community assembly process strengthened with grazing time. (3) Traits related to the cycling of biological matter, such as leaf area (LA), SLA, reproductive height (RH), photosynthetic (PHO), and GF more frequently diverged after long-term grazing, especially in higher grazing areas. Community assembly in intensely grazed ecosystems takes over a decade to support fundamental functions, highlighting the need for grazing intensity thresholds for sustainable grassland use.

Rapid environmental changes across Europe include warmer and increasingly variable temperatures, changes in soil nutrient availability, and pollinator decline. These abiotic and biotic changes can affect natural plant populations and force them to optimize resource use against competitors. To date, the evolution of competitive ability in the context of changes in nutrient availability remains understudied. In this study, we investigated whether the common calcareous grassland herb Leontodon hispidus recently evolved its competitive ability and response to nutrient availability. We compared ancestors sampled in 1995 and descendants sampled in 2018 and applied a competition treatment in combination with weekly nutrient treatments (no fertilizer, nitrogen, phosphorus, and both). We found evidence for evolution of increased competitive ability, with descendants producing more vegetative biomass than ancestors when grown under competition. Furthermore, supplementing nutrients (especially N) reduced differences in competitive ability between ancestors and descendants, suggesting that nutrients are a limiting factor in interspecific competition, which could be linked to the decreasing nitrogen emissions into the atmosphere since the 1990s. Our study demonstrates rapid contemporary evolution of competitive ability, but also the complexity of the underlying processes of contemporary evolution, and sheds light on the importance of understudied potential selection agents such as nutrient availability.

Phenology is a major component of animals' breeding, as they need to adjust their breeding timing to match optimal environmental conditions. While the effects of shifting phenology are well-studied on populations, few studies emphasise its ecological causes and consequences at the inter-individual level. Using a 20-year monitoring of more than 2500 breeding events from ~ 500 breeding little penguins (Eudyptula minor), a very asynchronously breeding seabird, we investigated the consequences of late breeding on present and next breeding events. We found that individuals breeding later had reduced breeding success, lighter chicks at fledging, lower probability of laying a second clutch, and decreased parents' post-breeding body condition. Importantly, we found important cycling effects where delayed breeding during a given year led to significantly later laying date, lower breeding probability and lower breeding success when they breed during the next season, suggesting potential carry-over effects from one season to the next. To further understand the causes of such variability in phenology while earlier breeding is associated with better individual fitness, we aimed to assess intrinsic differences amongst individuals. We showed that the heterogeneity in breeding timing was partly fixed, the laying date being a significantly repeatable behaviour (17%), asking for more studies on heritability or early-development effects. This extensive study highlights the combined roles of carry-over effects and intrinsic differences on individual phenology, with important implications on breeding capacity through life.

Accurate identification of decreasing trends is a prerequisite for successful conservation, but can be challenging when immigration compensates local declines in abundance. Here, we show that a potential declining trend driven by low vital rates was overridden and converted into a spectacular increase by massive immigration into the population of a semi-social raptor, the black kite Milvus migrans, breeding in a highly contaminated area near a major landfill. Immigration was promoted by a growing food-base of live prey, coupled with the attraction exerted by the progressive gathering of a large flock of non-breeders at the area, resulting in an "attraction spiral" that lured large numbers of breeders to settle into a contaminated population incapable of self-sustenance. Immigration was so prevalent that, in little more than a decade, over 95% of the original population was substituted by immigrants, which showed the enormous potential of immigration as a rescue mechanism. At the same time, immigration may hide cryptic threats, as shown here, and expose some species, especially group-living mobile ones, to rapid attraction to anthropogenic subsidies, whose potential role as evolutionary traps is well known. The dynamics exposed here may become increasingly common, affecting many other species in our growingly anthropogenic world. Our results remark the often overlooked importance of immigration in ecology, evolution, and conservation as a key player for population dynamics and their more realistic forecast.

Nitrogen deposition continues to change grassland plant community composition particularly in more mesic systems; however, whether these altered plant communities will respond differently to other global change factors remains to be seen. Here, we explore how nutrient-altered tallgrass prairie responds to drought. Seven years of nutrient treatments (control, nitrogen (N), phosphorus (P), and N + P) resulted in significantly different plant communities. Within this experimental context we imposed a 3-year drought followed by 3 years of recovery from drought. The response of plant functional types depended on the nutrient treatment. During recovery years, C₄ grasses recovered in the first year in all treatments but the N + P treatment, where instead annual grasses increased. These differential responses during recovery resulted in greater shifts in community composition in the N + P treatment compared with the controls. Despite the effects on community composition, we found no interaction between nutrient treatment and drought treatment on species richness or evenness and standing biomass during drought or recovery. We found drought induced shifts in plant functional groups led to the composition of previously droughted N + P plot becoming more dominated by annual grasses during the recovery years, likely creating a lasting legacy of drought.

An animal's diet breadth is a central aspect of its life history, yet the factors determining why some species have narrow dietary breadths (specialists) and others have broad dietary breadths (generalists) remain poorly understood. This challenge is pronounced in herbivorous insects due to incomplete host plant data across many taxa and regions. Here, we develop and validate machine learning models to predict pollen diet breadth in bees, using a bee phylogeny and occurrence data for 682 bee species native to the United States, aiming to better understand key drivers. We found that pollen specialist bees made an average of 72.9% of their visits to host plants and could be predicted with high accuracy (mean 94%). Our models predicted generalist bee species, which made up a minority of the species in our dataset, with lower accuracy (mean 70%). The models tested on spatially and phylogenetically blocked data revealed that the most informative predictors of diet breadth are plant phylogenetic diversity, bee species' geographic range, and regional abundance. Our findings also confirm that range size is predictive of diet breadth and that both male and female specialist bees mostly visit their host plants. Overall, our results suggest we can use visitation data to predict specialist bee species in regions and for taxonomic groups where diet breadth is unknown, though predicting generalists may be more challenging. These methods can thus enhance our understanding of plant-pollinator interactions, leading to improved conservation outcomes and a better understanding of the pollination services bees provide.

Anthropogenic climate change poses a significant threat to species on the brink of extinction. Many non-avian reptiles are endangered, but uncovering their vulnerability to climate warming is challenging, because this requires analyzing the climate sensitivity of different life stages and modeling population growth rates. Such efforts are currently hampered by a lack of long-term life-history data. In this study, we used over 3 decades of mark-recapture data from a natural population of the endangered meadow viper (Vipera ursinii ursinii) to unravel the patterns of temporal variation in reproductive traits, the local climatic determinants of inter-annual variation in reproduction, and the potential buffering effects of life cycle on population growth rate. We found significant inter-annual variation in body growth, gestation length, post-parturition body condition, clutch success, and offspring traits at birth, while reproductive effort showed little temporal variation. Temperature during gestation was the most critical factor, reducing gestation length and increasing both clutch success and post-parturition body condition. In contrast, neither air humidity nor global radiation affected reproductive outcomes. This population had a negative growth rate with minimal temporal variation, indicating a rapid decline largely independent of climatic conditions. Overall, the viper's life-history traits appeared to be buffered against temporal variation in climatic conditions, with this declining population potentially benefiting on the short term from rising local temperatures.

Among the many changes associated with the urbanization process, changes in resource availability can directly impact local wildlife populations. Urban areas suppress native vegetation and convert natural environments into impervious surfaces, modifying the composition and quantity of available food resources. Understanding the food requirements of species is crucial, mainly because it is one of the main elements that characterize their ecological niche and structure local communities. Our aim in this study was to assess the impact of urbanization intensity on the isotopic niche space of birds commonly found in urban areas of Brasília, the capital of Brazil, a big city in central Brazil with approximately 3 million inhabitants. By analyzing the δ¹³C and δ¹⁵N isotopic metrics of feathers from bird species found along a gradient of urbanization intensity, we evidenced a simplification but not a displacement of the bird assembly isotopic space due to urban intensification. Bird assemblage access similar food resources in the higher urban intensification areas, although less diversified than in lower urban intensification areas. In most cases, the response to urban intensification is more specific than convergent among guild members. The studied species maintain themselves in highly intensified urban areas by restricting, changing, and expanding their access to resources. The trophic dimension is one of the key components of the species' ecological niche, and understanding the urban intensification impacts on this dimension is essential for maintaining biodiversity and ecosystem services in cities.