Seasonal Environments Research Articles

Seasonal urban surface thermal environment analysis based on local climate zones: A case study of Chongqing

The rapid urbanization has exacerbated the heat island effect, impacting city development and residents' health. This study, using Local Climate Zones (LCZ) as a framework, connects spatial structure, resource allocation, and thermal environment research. It investigates the spatiotemporal heterogeneity of the surface thermal environment and its driving forces, crucial for mitigating heat issues. Utilizing various data sources like remote sensing images, road network data, land use data, high-resolution street view data, and building data, the research employs the random forest algorithm to map LCZs in Chongqing's central urban area. Through mathematical statistics, equi-sector analysis, ring-layer analysis, and Pearson correlation analysis, the study examines seasonal variations in spatiotemporal heterogeneity and driving mechanisms of the surface thermal environment. Key findings include: (1) The central urban area of Chongqing is dominated by open-building and vegetation-type LCZs, with building-type LCZs showing a “clustered” distribution, while natural-type LCZs are mainly found in the suburbs with ribbon and block distribution in the urban area. (2) The surface thermal environment in the study area correlates strongly with surface cover and exhibits significant high temperature effects in summer. (3) The surface thermal conditions vary significantly among different LCZs and exhibit seasonal patterns, natural-type LCZs generally have lower temperatures compared to building-type LCZs.(4) The surface thermal characteristics within the same category of LCZs in different locations display distinct differences and seasonal variations. (5) The internal temperatures of LCZs are significantly linked to four surface attributes, each displaying seasonal fluctuations. Greenness, height, and wetness are inversely related to the surface thermal conditions, while brightness shows a positive correlation. Both seasonal variations and LCZ types differences have a noticeable influence on their respective driving mechanisms to some degree.

Clockwork precision: egg-laying-induced rise of body temperature is seasonally programmed in a wild bird

There is long time interest about the phenology of plants and animals living in seasonal environments as research in that field would help to understand the coping mechanisms leading to a higher fitness. For instance, it has been shown several decades ago that birds prepare themselves 2–4 months before the actual start of the breeding season by slowly growing reproductive organs. In parallel, the resting metabolic rate increase during reproduction in various vertebrates including mammals, reptiles, and birds. Recently, it has been reported that body temperature of a marine bird species was reaching an annual peak during egg-laying, raising the question about the seasonal dynamic of this important physiological feature. Using data loggers implanted in the abdominal cavity of female Common Eiders (Somateria mollissima mollissima) for a full year, we show here that daily body temperature (Tb.daily) is slowly increasing first and then accelerating at the approach of the laying period. Because the rise of Tb.daily is tightly associated with egg-laying in this species, we also analysed the influence of ambient temperature (water and air) and photoperiod on this seasonal dynamic. Based on the various mechanisms at work and a parsimonious interpretation of the data, we conclude that photoperiod is the main cue driving the seasonal breeding program of eiders. Although the laying dates of the instrumented females were highly clustered over a period of 4 years, we speculated that the remaining variation observed was the result of eco-physiological challenges occurring over the years.

Availability of alternative prey rather than intraguild interactions determines the local abundance of two understudied and threatened small carnivore species.

Intraguild interactions influence the structure and local dynamics of carnivore mammals' assemblages. The potential effects of these interactions are often determined by the body size of competing members and may result in negative relationships in their abundance and, ultimately, lead to species exclusion or coexistence. The relative importance of interspecific interactions along with landscape characteristics in determining population patterns of understudied and threatened sympatric small carnivores, such as skunks, remains poorly documented. Therefore, we assessed the spatiotemporal variation in the abundance of American hog-nosed skunks Conepatus leuconotus and pygmy spotted skunks Spilogale pygmaea and the effect of interspecific interactions, resource availability, and habitat complexity on their local abundance in areas with the deciduous tropical forest south of the Mexican Pacific slope. We used presence-absence data for skunk species from three camera-trapping surveys between 2018 and 2020 in combination with Royle-Nichols occupancy models fitted in a Bayesian framework to estimate abundance, incorporating the effects of covariates related to the factors evaluated. We analyzed the relationship between the abundances of skunks using Bayesian Generalized Linear Models. Both skunk species showed significant differences in their abundances between seasons and between study sites. Overall, pygmy skunks were more abundant than hog-nosed skunks. We found negative relationships among the relative abundances of skunks during the dry seasons, but no evidence that local abundance is governed by the competitive dominance of the larger species. Patterns of skunk abundance were better explained by prey availability and other predictors related to habitat complexity, rather than interspecific interactions, since these models showed the highest predictive accuracies and strong positive and negative relationships. Our study highlights the underlying factors that determine the local abundance of these understudied and threatened small carnivores, allowing us to better understand the mechanisms that govern their coexistence for effective management and conservation of species in seasonal environments.

Mathematical Analysis for Honeybee Dynamics Under the Influence of Seasonality

In this paper, we studied a mathematical model for honeybee population diseases under the influence of seasonal environments on the long-term dynamics of the disease. The model describes the dynamics of two different beehives sharing a common space. We computed the basic reproduction number of the system as the spectral radius of either the next generation matrix for the autonomous system or as the spectral radius of a linear integral operator for the non-autonomous system, and we deduced that if the reproduction number is less than unity, then the disease dies out in the honeybee population. However, if the basic reproduction number is greater than unity, then the disease persists. Finally, we provide several numerical tests that confirm the theoretical findings.

Measuring behavioral synchronization and spatial cohesion in the activity budgets of three adult white-handed gibbon (Hylobates lar) dyads in Huai Kha Khaeng Wildlife Sanctuary, Thailand.

Individual behavior of primates living in small groups is often seen to represent behavior of all group members due to close spatial cohesion. However, given that females expend more energy on reproduction than males (including lactation and infant carrying), females and males may exhibit different behaviors even when maintaining spatial proximity, particularly in highly seasonal or resource-poor environments. We collected 187 hours of data from three dyads (n= 6 individuals) of white-handed gibbons (Hylobates lar) living in a fruit-poor environment in western Thailand during the period of fruit scarcity. We calculated activity budgets, dyad behavioral synchronization, and dyad spatial cohesion. We hypothesized that activity budgets would differ significantly between sexes or pairs would engage in behaviors independently to provide females with an opportunity to obtain more resources. We also hypothesized that pairs would remain in close proximity. Overall, activity budgets exhibited significant variation when analyzed by sex (X2= 27.693, P ⩽ 0.001) and group (X2= 119.584, P ⩽ 0.001). Females spent less time resting and vocalizing and more time traveling compared to males. Percentages of synchronized behavior were lower than expected with only 55% of records synchronized (group B: 58.6%; group D: 58.5%; group L: 49.7%). Spatial cohesion, however, was relatively high overall with adults in the same or adjacent trees in 67.1% of paired records but significantly variable across groups (B: 89.4%; D: 73.1%; L: 48.2%; X2= 190.111, P ⩽ 0.001). We suggest that behavioral synchronization and spatial cohesion may be indicators of pair bond strength, not just the result of pair living. Given differences in activity budgets, low behavioral synchronization, and variable amounts of time pair mates spent apart, we conclude that pair mates should be considered individual actors who engage in behaviors independently from one another, particularly when coping with challenging ecological conditions.

Gastrointestinal morphology is an effective functional dietary proxy that predicts small mammal community structure.

The availability and quality of food resources can alter the intensity of competition and predation pressure within communities. Understanding species capacity to respond to global change-driven shifts in resource distribution is therefore crucial for biodiversity conservation. Small mammal communities are often structured by competition for food resources, but understanding and monitoring these processes are currently hindered by lack of functional dietary trait information in these hard-to-sample systems. In this study, we collected a comprehensive suite of gastrointestinal (GI) measurements from 26 small mammal species (including some never reported), compared them with more traditional craniodental traits in predicting dietary guild, and used them in a novel way to understand how diet structures 22 small mammal communities across the Appalachian Mountains of eastern North America. As predicted, we found GI traits to be effective dietary trait proxies; they were equally or more accurate than craniodental proportions in predicting the dietary guild of individual species. Furthermore, at the community level, we found that both the mean and functional dispersion of GI length were positively correlated with latitude and measures of temperature seasonality. Our results indicate that small mammal communities in more seasonal environments are filtered to include species with longer GI tracts (on average) as well as those that can partition food resources more finely, as expected based on the lower productivity of these regions. Conversely, communities in less seasonal environments display functional redundancy from the addition of species with short to intermediate GI lengths. Proportions of the GI tract represent novel dietary traits that can illuminate community assembly processes across regional environmental gradients and in the face of changing timing and availability of resources.

Energy-Efficient Architectural Design of a Banquet Hall with Integrated Tunnel Ventilation: Monitoring Performance During the Transitional Season in China

The construction industry, a significant contributor to global energy consumption and greenhouse gas emissions, is under considerable pressure to adopt transformative approaches. Public buildings, which account for a substantial portion of total energy usage, must balance high standards of thermal comfort with ventilation efficiency. In China, many public buildings are part of urban landscapes, where façade designs often limit natural ventilation. Consequently, technologies like earth-to-air heat exchangers and wind towers are increasingly essential for enhancing natural ventilation. However, research on the efficacy of these systems remains sparse. This study examines the transitional seasonal environment by evaluating the thermal-humidity index of a banquet hall equipped with an earth-to-air heat exchanger system. Using DeST software [DeST 2.0], the study simulates indoor natural ventilation, calculates ventilation rates, and assesses residual heat removal efficiency. The system’s performance is also modeled under various thermal design zones. Results demonstrate that under natural ventilation, the system can achieve a residual heat removal efficiency of up to 490%. Simulations across different climate zones indicate that the system performs best in regions with extreme temperature fluctuations, particularly those with hot summers and warm winters. In these areas, the system reduces the annual temperature difference by up to 56.7%, significantly improving thermal comfort and reducing dependency on air conditioning. In contrast, performance in milder regions like Kunming achieves only a 37.5% reduction in temperature difference. Overall, this study provides valuable insights into energy-efficient design strategies and thermal optimization for banquet halls, with significant potential for energy savings and enhanced occupant comfort.

Insect responses to seasonal time constraints under global change are facilitated by warming and counteracted by invasive alien predators.

In seasonal environments, organisms with complex life cycles not only contend with seasonal time constraints (TC) but also increasingly face global change stressors that may interfere with responses to TC. Here, we tested how warming and predator stress imposed during the egg and larval stages shaped life history and behavioural responses to TC in the temperate damselfly Ischnura elegans. Eggs from early and late clutches in the season were subjected to ambient and 4°C warming temperature and the presence or absence of predator cues from perch and signal crayfish. After hatching, larvae were retained at the same thermal regime, and the predator treatment was continued or not up to emergence. The late eggs decreased their development time, especially under warming and when not exposed to predator cues. However, the late eggs increased their development time when exposed to predator cues, especially to crayfish cues. The TC decreased survival of late larvae that were as eggs exposed to crayfish cues, indicating a carry-over effect. The TC and warming additively reduced late larvae development time to emergence. Independent of the TC, predator cue effects on development time were stronger during the egg than during the larval stage. The late individuals expressed lower mass at emergence, which mirrored the size difference between field-collected mothers. Warming caused a higher mass at emergence. The late individuals increased their boldness and showed a higher number of moves, whereas warming caused a decreased boldness. There was no predator cue effect on larval behaviour. The results indicate that late individuals compensate for late season egg laying, which is facilitated under warming but counteracted under predation risk, especially when imposed by the crayfish.

Larval growth rate is not a major determinant of adult wing shape and eyespot size in the seasonally polyphenic butterfly Melanitis leda.

Insects often show adaptive phenotypic plasticity where environmental cues during early stages are used to produce a phenotype that matches the environment experienced by adults. Many tropical satyrine butterflies (Nymphalidae: Satyrinae) are seasonally polyphenic and produce distinct wet- and dry-season form adults, providing tight environment-phenotype matching in seasonal environments. In studied Mycalesina butterflies, dry-season forms can be induced in the laboratory by growing larvae at low temperatures or on poor food quality. Since both these factors also tend to reduce larval growth rate, larval growth rate may be an internal cue that translates the environmental cues into the expression of phenotypes. If this is the case, we predict that slower-growing larvae would be more likely to develop a dry-season phenotype. We performed the first experimental study on seasonal polyphenism of a butterfly in the tribe Melanitini. We measured both larval growth rate and adult phenotype (eyespot size and wing shape) of common evening brown butterflies (Melanitis leda), reared at various temperatures and on various host-plant species. We constructed provisional reaction norms, and tested the hypothesis that growth rate mediates between external cues and adult phenotype. Reaction norms were similar to those found in Mycalesina butterflies. We found that both among and within treatments, larvae with lower growth rates (low temperature, particular host plants) were more likely to develop dry-season phenotypes (small eyespots, falcate wing tips). However, among temperature treatments, similar growth rates could lead to very different wing phenotypes, and within treatments the relationships were weak. Moreover, males and females responded differently, and eyespot size and wing shape were not strongly correlated with each other. Overall, larval growth rate seems to be weakly related to eyespot size and wing shape, indicating that seasonal plasticity in M. leda is primarily mediated by other mechanisms.

Seasonal changes in hydraulic functions of eight temperate tree species: divergent responses to freeze-thaw cycles in spring and autumn.

Freeze-thaw cycles (FTCs) are the major seasonal environment stress in the temperate and boreal forests, which induces hydraulic dysfunction and limits tree growth and distribution. There are two types of FTCs in the field: FTCs with increasing temperature from winter to spring (spring FTCs); and FTCs with decreasing temperature from autumn to winter (autumn FTCs). While previous studies have evaluated the hydraulic function during the growing season, its seasonal changes and how it adapts to different types of FTCs remain unverified. To fill this knowledge gap, the eight tree species from three wood types (ring- and diffuse-porous, tracheid) were selected in a temperate forest undergoing seasonal FTCs. We measured the branch hydraulic traits in spring, summer, autumn, and early, middle, and late winter. Ring-porous trees always showed low native hydraulic conductance (Kbranch), and high percentage loss of maximum Kbranch (PLCB) and water potential that loss of 50% maximum Kbranch (P50B) in non-growing seasons (except summer). Kbranch decreased, and PLCB and P50B increased in diffuse-porous trees after several spring FTCs. In tracheid trees, Kbranch decreased after spring FTCs while the P50B did not change. All sampled trees gradually recovered their hydraulic functions from spring to summer. Kbranch, PLCB, and P50B of diffuse-porous and tracheid trees were relatively constant after autumn FTCs, indicating almost no effect of autumn FTCs on hydraulic functions. These results suggested that hydraulic functions of temperate trees showed significant seasonal changes, and spring FTCs induced more hydraulic damage (except ring-porous trees) than autumn FTCs, which should be determined by the number of FTCs and trees' vitality before FTCs. These findings advance our understanding of seasonal changes in hydraulic functions and how they cope with different types of freeze-thaw cycles in temperate forests.

Cold Coastal City Neighborhood Morphology Design Method Based on Multi-Objective Optimization Simulation Analysis

In the context of global warming and the frequent occurrence of extreme weather, coastal cities are more susceptible to the heat island effect and localized microclimate problems due to the significant influence of the oceanic climate. This study proposes a computer-driven simulation optimization method based on a multi-objective optimization algorithm, combined with tools such as Grasshopper, Ladybug, Honeybee and Wallacei, to provide scientific optimization decision intervals for morphology control and evaluation factors at the initial stage of coastal city block design. The effectiveness of this optimization strategy is verified through empirical research on typical coastal neighborhoods in Dalian. The results show that the strategy derived from the multi-objective optimization-based evaluation significantly improves the wind environment and thermal comfort of Dalian neighborhoods in winter and summer: the optimization reduced the average wind speed inside the block by 0.47 m/s and increased the UTCI by 0.48 °C in winter, and it increased the wind speed to 1.5 m/s and decreased the UTCI by 0.59 °C in summer. This study shows that the use of simulation assessment and multi-objective optimization technology to adjust the block form of coastal cities can effectively improve the seasonal wind and heat environment and provide a scientific basis for the design and renewal of coastal cities.

Season-specific genetic variation underlies early-life migration in a partially migratory bird.

Eco-evolutionary responses to environmentally induced selection fundamentally depend on magnitudes of genetic variation underlying traits that facilitate population persistence. Additive genetic variances and associated heritabilities can vary across environmental conditions, especially for labile phenotypic traits expressed through early life. However, short-term seasonal dynamics of genetic variances are rarely quantified in wild populations, precluding inference on eco-evolutionary outcomes in seasonally dynamic systems. This limitation applies to seasonal migration versus residence, constituting one key trait where rapid microevolution could rescue partially migratory populations from changing seasonal environments. We fitted novel quantitative genetic 'capture-recapture animal models' to multi-generational pedigree and year-round resighting data from 11 cohorts of European shags (Gulosus aristotelis), to estimate season-specific additive genetic variances in liabilities to migrate, and in resulting expression of migration, in juveniles' first autumn and winter. We demonstrate non-negligible genetic variation underlying early-life migration, with twice as large additive genetic variances and heritabilities in autumn than winter. Since early-life survival selection on migration typically occurs in winter, highest genetic variation and strongest selection are seasonally desynchronized. Our results reveal complex within- and among-year dynamics of early-life genetic and phenotypic variation, demonstrating that adequate inference of eco-evolutionary outcomes requires quantifying microevolutionary potential on appropriate scales and seasonal timeframes.

Behavioral adaptation to seasonal resource scarcity by Caribou (Rangifer tarandus) and its role in partial migration

Abstract Animals living in seasonal environments have adopted a wide array of tactics used to deal with seasonal resource scarcity. Many species migrate between habitats to reach areas where food resources are more plentiful as an attempt to address energetic demands through foraging. We assessed the winter behavioral adaptations of Caribou (Rangifer tarandus), a large ungulate inhabiting Arctic and sub-Arctic regions known for seasonal resource scarcity. Movement rates of Caribou are the lowest of the year during winter, revealing 1 mechanism individuals use to reduce energy expenditures. However, migratory individuals moved nearly twice as much as nonmigratory individuals during winter, suggesting that migratory individuals rely more upon income (forage), whereas nonmigratory individuals rely more upon capital (bodily reserves). Lichens are the primary winter forage for large, migratory herds of Caribou, and migratory individuals experienced more than 2.5 times greater lichen cover than nonmigratory individuals. We documented that both groups slowed their movement in areas of greater lichen cover, suggesting increased foraging time in these areas. Movement rates were greater near villages, which may be suggestive of disturbance, but the effect was weak. Overall energy saved by reduced movement rates was modest. However, energy savings were 11% of daily body energy lost or 47% of the demands of early pregnancy, which potentially could affect individual condition and/or fetal growth if not offset by increases in forage intake.

Fitness consequences of anthropogenic subsidies for a partially migratory wading bird.

Human activities are forcing wildlife to confront selective pressures different from those under which they evolved. In seasonal environments, migration evolved as an adaptation to fluctuating resource availability. Anthropogenic subsidies modify resource dynamics by providing a steady food source that is not subject to seasonality. Globally, many migratory populations are becoming increasingly resident in response to food supplementation. While these population-level shifts are assumed to arise from changing fitness consequences of individual behaviour in response to resource dynamics, these mechanisms are often difficult to quantify and disentangle. Here, we quantified fitness consequences of responses to anthropogenic subsidies in partially migratory wood storks (Mycteria americana) in the heavily urbanized southeastern United States. First, we tested whether individual migratory behaviour is linked to different responses to anthropogenic subsidies. Second, we quantified fitness consequences of these behavioural responses. We found that, in our system, migration and residency are alternative behavioural tactics associated with different responses to food supplementation. In turn, the use of anthropogenic resources alters a fitness component by enhancing nest survival. These results provide a mechanistic examination of how animals may respond to human-modified resource dynamics and how fitness consequences of individual tactics may translate into behavioural shifts at the population level.

Early-life variation in migration is subject to strong fluctuating survival selection in a partially migratory bird.

Population dynamic and eco-evolutionary responses to environmental variation and change fundamentally depend on combinations of within- and among-cohort variation in the phenotypic expression of key life-history traits, and on corresponding variation in selection on those traits. Specifically, in partially migratory populations, spatio-seasonal dynamics depend on the degree of adaptive phenotypic expression of seasonal migration versus residence, where more individuals migrate when selection favours migration. Opportunity for adaptive (or, conversely, maladaptive) expression could be particularly substantial in early life, through the initial development of migration versus residence. However, within- and among-cohort dynamics of early-life migration, and of associated survival selection, have not been quantified in any system, preventing any inference on adaptive early-life expression. Such analyses have been precluded because data on seasonal movements and survival of sufficient young individuals, across multiple cohorts, have not been collected. We undertook extensive year-round field resightings of 9359 colour-ringed juvenile European shags Gulosus aristotelis from 11 successive cohorts in a partially migratory population. We fitted Bayesian multi-state capture-mark-recapture models to quantify early-life variation in migration versus residence and associated survival across short temporal occasions through each cohort's first year from fledging, thereby quantifying the degree of adaptive phenotypic expression of migration within and across years. All cohorts were substantially partially migratory, but the degree and timing of migration varied considerably within and among cohorts. Episodes of strong survival selection on migration versus residence occurred both on short timeframes within years, and cumulatively across entire first years, generating instances of instantaneous and cumulative net selection that would be obscured at coarser temporal resolutions. Further, the magnitude and direction of selection varied among years, generating strong fluctuating survival selection on early-life migration across cohorts, as rarely evidenced in nature. Yet, the degree of migration did not strongly covary with the direction of selection, indicating limited early-life adaptive phenotypic expression. These results reveal how dynamic early-life expression of and selection on a key life-history trait, seasonal migration, can emerge across seasonal, annual, and multi-year timeframes, yet be substantially decoupled. This restricts the potential for adaptive phenotypic, microevolutionary, and population dynamic responses to changing seasonal environments.

Assessment of mercury methylation and methylmercury demethylation potentials in water and sediments along the Wabigoon River system

Monomethylmercury (MMHg) plays a crucial role in the accumulation of mercury (Hg) within aquatic food chains. Since ambient levels of methylmercury are governed by the balance of simultaneous methylation and demethylation processes, determining in situ methylation and demethylation rates is critically important to understand the dynamics of methylmercury in the environment. This is especially important in the Wabigoon River system in Ontario, Canada, which is severely contaminated with Hg by a chlor-alkali facility operating in the 1960s, and still exhibits some of the highest recorded fish mercury concentrations in Canada. This work used a simultaneous addition of isotope enriched Hg and MMHg tracers to ascertain Hg methylation and MMHg demethylation potentials. At the locations investigated for this study, the most favourable conditions for Hg methylation were found at the Hydroelectric dam, being able to transform 4.2 % and 4.4 % of added Hg in water and sediments per day, respectively, to MMHg. This could correspond to 1.9 ng/L and 29 ng/g of new MMHg being produced from current ambient Hg. Clay Lake, which is considered a sink for mercury and exhibiting a seasonal anoxic environment at its bottom waters, also demonstrated significant MMHg generation, being able to produce 2.7 ng/L and 13 ng/g of MMHg per day, respectively. Demethylation rates in sediments of riverbed and wetland locations showed an average half-life for methylmercury of 2.1 days, indicating a rapid turnover of MMHg in the Wabigoon River. However, significantly lower demethylation rates were also measured near the inflow of Clay Lake, where it took up to 144 days for MMHg to decrease by 50 %. Generally, most of the investigated locations downstream of the pollution source displayed the potential to generate methylmercury, which could be distributed throughout the Wabigoon River system and therefore require attention with respect to future remediation activities.

Leaf functional traits predict timing of nutrient resorption and carbon depletion in deciduous subarctic plants

Abstract Resorption of key elements promotes their conservation in plants in nutrient‐poor ecosystems. In seasonal environments, the timing of resorption is expected to influence resorption efficiency and plant fitness due to the trade‐off between maximizing photosynthetic carbon gain by late resorption and minimizing frost risks and nutrient loss by early resorption. Here, we hypothesize that (1) these alternative strategies with respect to the timing of element resorption both occur among summergreen species; (2) deciduous woody plants favour delayed resorption while herbaceous species benefit from gradual, early onset resorption; (3) this pattern is part of a more general relationship in which species with conservative resource economic traits have more delayed resorption. We measured nitrogen (N), phosphorus (P) and carbon (C) contents of mature, senescing and senesced leaves of 22 predominant plant species across four types of ecosystems in a subarctic region. We then calculated timing of resorption as the Julian calendar day of 50% of element resorption (T50), and examined its relationship with plant functional types and leaf resource economic traits (leaf mass per area [LMA], leaf C, N and P contents). The timing of N resorption in subarctic plants ranged from day 213 to 254, while the timing of P resorption ranged from day 211 to 261 and of C from day 214 to 260 across species. On average, the resorption of N and P and depletion of C were 13, 12 and 19 days respectively earlier in herbaceous plants than in woody ones. For all the three elements, T50 of plants decreased significantly with increasing acquisitive economic traits. Synthesis: As hypothesized, we found that (1) both “steady‐and‐slow” and “late‐and‐fast” strategies of resorption timing co‐occurred in a subarctic flora; consistent with these two strategies, herbaceous plants resorbed nutrients and carbon earlier than deciduous woody species; (2) relevant functional traits representing resource conservation were positively and linearly related to the timing of nutrient resorption and carbon depletion. These findings for element resorption timing have important implications for functional changes in the vegetation composition of seasonal regions in response to temperature fluctuations in a changing climate.

Water stress resilience in Mauritia flexuosa (Arecaceae) embryos: New insights into the persistence of recalcitrant seed banks

The neotropical palm Mauritia flexuosa produces seeds that show the association between recalcitrance and dormancy. Despite the intolerance to desiccation, the seeds can maintain persistent banks in flooded environment soils (veredas) in the Cerrado biome. As the mechanisms involved in the persistence of recalcitrant seed banks are still poorly understood, the objective of this work was to evaluate the response of M. flexuosa embryos to water deficit and saturation stresses. Embryos of M. flexuosa with water content typical of dispersion or subjected to hydration were exposed to moderate and severe water potentials (Ψw= −1.5 MPa and Ψw= −2.1 MPa), in addition to water saturation (Ψw= 0 MPa). Anatomical, histochemical and ultrastructural evaluations were performed on the embryos after 24 h. Membrane integrity estimation, endo-β-mannanase activity and oxidative stress indicators (H2O2 and MDA contents, CAT, SOD and APX activity) were also evaluated. The endosperm structure contributes to the maintenance of embryo hydration, while abundant mucilage reserves favor resilience to desiccation. Post-dispersal hydration makes embryos less vulnerable to oxidative stress, which is due to the non-enzymatic antioxidant system. Both moderate water stress and post-dispersal water absorption induce an increase in metabolism and the mobilization of reserves, which indicate that hydration/dehydration cycles can favor overcoming dormancy. M. flexuosa embryos show resilience to water deficit, and that is crucial for the persistence of seeds in the soil in seasonal environments, however, successful germination is dependent on high hydration, which prevents structural and physiological damage.

Mandibular ecomorphology in the genus ursus (Ursidae, Carnivora): relevance for the palaeoecological adaptations of cave bears (U. spelaeus) from Scladina cave

ABSTRACT Considerable morphological and ecological diversity has been found in extinct and extant members of the bear genus, Ursus, and appears to be key in explaining how they have thrived across vast ecological gradients. One example is the cave bear Ursus spelaeus. We applied 2D geometric morphometric techniques to describe morphological changes in the mandibles of extant Ursus species to further interpret the palaeoecology of U. spelaeus. Ursus species were discriminated using their mandibular morphology, which showed intra and interspecific shape variation that was indirectly linked to climatic adaptations through dietary variation. Mandibles of bears that inhabit colder, drier and more seasonal environments were generally slender with large diastema and a dorsoventrally smaller ramus. In contrast, species from warmer environments with higher levels of precipitation were found to have a dorsoventrally taller ramus (relative to the corpus). Discriminant function analyses of the morphology of U. spelaeus suggested adaptations to a series of fluctuating environments through time, helping to assess previously proposed Marine Isotope Stages for sedimentary deposits in Scladina Cave. Our geometric morphometrics analyses of bear mandibular ecomorphology demonstrates how geometric morphometrics provides a valuable tool to enhance paleoenvironmental reconstructions within deposits of the same fossil site.

Prediction of birthdates based on fetal development in Bighorn Sheep (Ovis canadensis)

Abstract Reproductive phenology is a critical element of how animals persist in their environment and affects survival of young, especially in seasonal environments. We investigated the correlation between fetal eye diameter and birth timing to determine if birthdates could be predicted by a prenatal metric. We used ultrasonography to measure eye diameters of fetuses and vaginal implant transmitters to determine birthdates of Rocky Mountain Bighorn Sheep (Ovis canadensis canadensis) in Wyoming, United States, from 2019 to 2023. Fetal eye diameter strongly predicted days until birth (β = −2.8; pseudo-R2 = 0.88). Effective prediction of birthdates via ultrasonography can yield opportunities for logistical planning in neonatal studies, monitoring changes in reproductive phenology, and evaluating questions of resource allocation relative to reproductive processes.