1. Animals exhibit varied life-history traits that reflect adaptive responses to their environments. For Arctic-breeding birds, traits like foraging guild, egg nutrient allocation, clutch size, and chick growth are predicted to be under increasing selection pressure due to rapid climate change and increasing environmental variability across high-latitude regions. 2. We compared four migratory birds (black brant [Branta bernicla nigricans], lesser snow geese [Chen caerulescens caerulescens], semipalmated sandpipers [Calidris pusilla], and Lapland longspurs [Calcarius lapponicus]) with varied life histories at an Arctic site in Alaska, USA, to understand how life-history traits help moderate environmental variability across different phases of the reproductive cycle. 3. We monitored aspects of reproductive performance related to the timing of breeding, reproductive investment, and chick growth from 2011–2018. 4. In response to early snow melt and warm temperatures, semipalmated sandpipers advanced their site arrival and bred in higher numbers, while brant and snow geese increased clutch sizes; all four species advanced their nest initiation dates. During chick rearing, longspur chicks were relatively resilient to environmental variation whereas warmer temperatures increased the growth rates of sandpiper chicks but reduced growth rates of snow goose goslings. These responses generally aligned with traits along the capital-income spectrum of nutrient acquisition and altricial-precocial modes of chick growth. Under a warming climate, the ability to mobilize endogenous reserves likely provides geese with relative flexibility to adjust the timing of breeding and the size of clutches. Warmer temperatures, however, may negatively affect the quality of herbaceous foods and slow gosling growth. 5. Species may possess traits that are beneficial during one phase of the reproductive cycle and others that may be detrimental at another phase, uneven responses that may be amplified with future climate warming. These results underscore the need to consider multiple phases of the reproductive cycle when assessing the effects of environmental variability on Arctic-breeding birds.
Acoustic communication allows animals to coordinate and optimize resource utilization in space. Cardioderma cor, the heart-nosed bat, is one of the few species of bats known to sing during nighttime foraging. Previous research found that heart-nosed bats react aggressively to song playback, supporting the territorial defense hypothesis of singing in this species. By tracking 14 individuals nightly during the dry seasons in Tanzania we further investigated the territorial defense hypothesis from an ecological standpoint, which predicts singing should be associated with exclusive areas containing a resource. We quantified the singing behavior of individuals at all perches used throughout the night. Using home range analysis tools, we quantified overall use night ranges and singing ranges, as well as areas used in early and later time periods at night. Males engaged in antiphonal singing from small (x̄ = 3.48 ± 2.71 ha), largely exclusive areas that overlapped with overall night ranges used for gleaning prey. Individuals varied in singing effort; however, all sang significantly more as night progressed. Subsequently, areas used earlier at night and overall use areas were both larger than singing areas. Individuals varied in singing strategies. Some males sang for long periods in particular trees and had smaller core areas, while others moved frequently among singing trees. The most prolific singers used more perches overall. The results support the hypothesis that acoustic communication repertoires evolved in support of stable foraging territory advertisement and defense in some bats.
Aridity and intensive grazing have been confirmed to affect the facilitative effects of dryland shrubs. However, their combined effects on plant-plant interactions have rarely been tested. To test how these two factors affect relations between plants, we analyzed 144 plots (under shrub canopy vs. open areas) at 12 sampling areas established in the conditions of two grazing regimes (high grazing vs. low grazing intensity) and two different climatic regions (arid vs. semi-arid) in northeastern Iran. A dominant shrub, Artemisia kopetdaghensis, was selected as the model species. Further, we studied changes in plant life strategies along the combined grazing and aridity stress gradients. We used relative interaction indices to test the outcomes of plant-plant interactions, calculated for species richness, Shannon diversity and species abundances. Then we compared them using linear mixed-effect models (LMM). The indicator species analysis was used to identify species typical for the under-canopy of shrub and for the adjacent open areas. The combination of stress factors affected the type and intensity of plant-plant interactions and plant life strategies (CSR) of the indicator species. Artemisia kopetdaghensis showed the highest facilitation effect under the most intensive stress conditions (high aridity/high grazing), which turned into competition under the low stress conditions (low aridity/low grazing). In the arid region, the canopy of shrub protected ruderal annual forbs and grasses with SR and R-strategy, respectively, in both high (high aridity/high grazing) and low grazing intensity (high aridity/low grazing). In the semi-arid region and high grazing intensity (low aridity/high grazing), the shrubs protected perennial forbs with C-strategy. Our FINDINGS highlight the importance of context-dependent shrub management in the restoration of vegetation damaged by intensive grazing.
1. Ecologically meaningful seed germination experiments are constrained by access to seeds and relevant environments for testing at the same time. This is particularly the case when research is carried out far from the native area of the studied species. 2. Here, we demonstrate an alternative - the use of glass houses in botanic gardens as simulated-natural habitats to extend the ecological interpretation of germination studies. Our focal taxa were banana crop wild relatives (Musa acuminata subsp. burmannica, M. acuminata subsp. siamea and M. balbisiana), native to tropical and subtropical Southeast Asia. Tests were carried out in Belgium, where we performed germination tests in relation to exposure to sun and foliage-shading, seed burial-depth in different heated glass house compartments, as well as seed survival and dormancy release in the soil. We anchored the interpretation of these studies by also conducting an experiment in a semi-natural habitat in the species native range (M. balbisiana - Los Baños, the Philippines), where we tested germination responses to exposure to the sun and shade. Using temperature data loggers, we determined temperature dynamics suitable for germination in both these settings. 3. In semi-natural and simulated-natural habitats, seeds germinated in response to exposure to direct solar radiation. Seed burial-depth had a significant but marginal effect by comparison, even when seeds were buried to 7cm in the soil. Temperatures at sun-exposed compared to shaded environments differed by only a few degrees Celsius. Maximum temperature of the period prior to germination was the most significant contributor to germination responses and germination increased linearly above a threshold of 23°C to the maximum temperature in the soil (in simulated natural habitats) of 35°C. 4. Glass houses can provide useful environments to aid interpretation of seed germination responses to environmental niches.
Offshore wind energy is a growing industry in the United States, and renewable energy from offshore wind is estimated to double the country's total electricity generation. There is growing concern that land-based wind development in North America is negatively impacting bat populations, primarily long-distance migrating bats, but the impacts to bats from offshore wind energy is unknown. Bats are associated with the terrestrial environment, but have been observed over the ocean. In this review, we synthesize historic and contemporary accounts of bats observed and acoustically recorded offshore over North American waters to ascertain the spatial and temporal distribution of bats flying offshore. We integrate these records with studies of offshore bats in Europe and of bat behavior at land-based wind energy studies to examine how offshore wind development could impact North American bat populations. We find that most offshore bat records are of long-distance migrating bats and records occur during autumn migration, the period of highest fatality rates for long-distance migrating bats at land-based wind facilities in North America. We summarize evidence that bats may be attracted to offshore turbines for roosting and foraging opportunities, potentially increasing their risk of collision, but that higher wind speeds offshore can potentially reduce the amount of time that bats are exposed to risk. We identify knowledge gaps and hypothesize that a combination of mitigation strategies may be the most effective approach for minimizing impacts to bats and maximizing offshore energy production.
Adaptive evolutionary theory argues that organisms with larger effective population size (Ne) should have higher rates of adaptive evolution and therefore greater capacity to win evolutionary arm races. However, in some certain cases species with much smaller Ne may be able to survive beside their opponents for an extensive evolutionary time. Neutral theory predicts that accelerated rates of molecular evolution in organisms with exceedingly small Ne is due to the effects of genetic drift and fixation of slightly deleterious mutations. We test this prediction in two obligate social parasite species and their respective host species from the bee tribe Allodapini. The parasites (genus Inquilina) have been locked into a tight coevolutionary arm races with their exclusive hosts (genus Exoneura) for ~15 million years, even though Inquilina exhibit Ne that are an order of magnitude smaller than their host. In this study, we compared rates of molecular evolution between host and parasite using nonsynonymous to synonymous substitution rate ratios (dN/dS) of eleven mitochondrial protein coding genes sequenced from transcriptomes. Tests of selection on mitochondrial genes indicated no significant differences between host and parasite dN/dS, with evidence for purifying selection acting on all mitochondrial genes of host and parasite species. Several potential factors which could weaken the inverse relationship between Ne and rate of molecular evolution are discussed.
Identification of phenotypic characteristics in reproductively successful individuals provides important insights into the evolutionary processes that cause range shifts due to environmental change. Female beluga whales (Delphinapterus leucas) from the Baffin Bay region (BB) of the Canadian Arctic in the core area of the species’ geographic range have larger body size than their conspecifics at the southern range periphery in Hudson Bay (HB). We investigated the mechanism for this north and south divergence as it relates to ovarian reproductive activity (ORA = total corpora) that combines morphometric data with ovarian corpora counted from female reproductive tracts. Based on the previous finding of reproductive senescence in older HB females, but not for BB whales, we compared ORA patterns of the two populations with age and body length. Female beluga whale ORA increased more quickly with age (63% partial variation explained) in BB than in HB (41%). In contrast, body length in HB female beluga whales accounted for considerably more of the total variation (12 vs 1%) in ORA compared to BB whales. We speculate that female HB beluga whale ORA was more strongly linked with body length due to higher population density resulting in food competition that favors the energetic advantages of larger body size during seasonal food limitations. Understanding the evolutionary mechanism of how ORA varies across a species’ range will assist conservation efforts in anticipating and mitigating future challenges associated with a warming planet.
1. Neighborhood competition models are powerful tools to measure the effect of interspecific competition. Statistical methods to ease the application of these models are currently lacking. 2. We present the forestecology package providing methods to i) specify neighborhood competition models, ii) evaluate the effect of competitor species identity using permutation tests, and iii) measure model performance using spatial cross-validation. Following Allen (2020), we implement a Bayesian linear regression neighborhood competition model. 3. We demonstrate the package’s functionality using data from the Smithsonian Conservation Biology Institute’s large forest dynamics plot, part of the ForestGEO global network of research sites. Given ForestGEO’s data collection protocols and data formatting standards, the package was designed with cross-site compatibility in mind. We highlight the importance of spatial cross-validation when interpreting model results. 4. The package features i) tidyverse-like structure whereby verb-named functions can be modularly “piped” in sequence, ii) functions with standardized inputs/outputs of simple features ‘sf‘ package class, and iii) an S3 object-oriented implementation of the Bayesian linear regression model. These three facts allow for clear articulation of all the steps in the sequence of analysis and easy wrangling and visualization of the geospatial data. Furthermore, while the package only has Bayesian linear regression implemented, the package was designed with extensibility to other methods in mind.
We praise the authors for their work, and for the lyric title of their paper. We give a concise sketch of the present level of understanding of Quercus forest in Colombia. We identify the shortcomings in this published paper. We improve the relevance of this paper about Quercus as well as for future phylogenetic investigations other montane forest taxa to be framed in the rapidly improving palaeoecological understanding of the Northern Andes.
Anderson’s White-bellied Rat, Niviventer andersoni (Thomas, 1911) (Muridae, Niviventer) is an species endemic to China. In the present study, we have sequenced the first complete mitochondrial genome of N. andersoni using next-generation sequencing. The 16,291 bp mitochondrial genome consists of 22 transfer RNA genes, 13 protein-coding genes (PCGs), two ribosomal RNA genes, and one non-coding control region (D-Loop). Phylogenetic analyses of the nucleotide sequences of all 13 PCGs, PCGs minus ND6 and the entire mitogenome sequence except for the D-loop, produce nearly identical, well-resolved topologies. Our results support that N. andersoni clustered with N. excelsior and form a sister group with N. confucianus, and they statistically reject the hypothesis from one cytochrome b (cytb) gene tree that N. confucianus is sister to N. fulvescens. Our research may be helpful to further reconsideration of clearer taxonomy and improve our understanding of mitogenomic evolution in the genus Niviventer.
Both the Norwegian Spring Spawning herring (Clupea harengus) and the Northeast Arctic cod (Gadus morhua) are examples of how the overexploitation of marine fish populations was leading to a strong reduction even so stock collapse, with a strong decline in the associated fisheries, followed by a recovery. Cod and herring are both part of the Barents Sea ecosystem, which experienced major warming events in the early (1920-1940) and late 20th century. While the collapse or near collapse of these stocks seems to be linked to instability created by overfishing and climate, the difference of population dynamics before and after is not fully understood. In particular, it is unclear how the changes in population dynamics before and after the collapses are associated with biotic interactions. The combination of the availability of unique long-term time series for herring and cod makes it a well-suited study system to investigate the effects of collapse. We examine how species interactions may differently affect the herring and cod population dynamic before and after a collapse. Particularly we explore, using a GAM modelling approach, how herring could affect cod and reciprocally. We found that the effect on herring of cod biomass that was generally positive (i.e., covariation) became negative after the collapse (i.e., predation or competition). Likewise a change occurred for the cod, the juvenile herring biomass that had no effect before the collapse had a negative one after. Our results indicate that population collapses may lead to altered inter-specific interactions as well as altered response to abiotic environmental variations. While the stocks are at similar abundance levels before and after the collapses the system is potentially different in its functioning and may require different management action.
Undergraduate field experiences (UFEs) are a prominent element of science education across many disciplines; however, empirical data regarding the outcomes are often limited. UFEs are unique in that they take place in a field setting, are often interdisciplinary, and include diverse students. UFEs range from courses, to field trips, to residential research experiences, and thereby have the potential to yield a plethora of outcomes for undergraduate participants. The UFE community has expressed a strong interest in better understanding how to assess the outcomes of UFEs. In response, we developed a strategy by which practitioners can assess their UFE using an evidence-based, systematic and iterative approach. This essay guides practitioners through the steps of: identifying intended UFE outcomes, considering contextual factors, determining an explicit assessment approach, and using the information to inform next steps. We provide a table of common learning outcomes and potential assessment tools, vignettes to illustrate using the strategy, and suggestions for practical application of the strategy. We aim to support comprehensive and aligned assessment of UFEs, leading to more inclusive and reflective design, and ultimately improved student outcomes. We urge practitioners to move towards evidence-based advocacy for continued support of UFEs.
Historically, bird song complexity was thought to evolve primarily through sexual selection on males, yet in many species both sexes sing. Previous research suggests competition for mates and resources during short, synchronous breeding seasons leads to more elaborate male songs at high latitudes. In contrast, we expect male-female song dimorphism and elaboration to be more similar at lower latitudes because longer breeding seasons and year-round territoriality yield similar social selection pressures in both sexes. However, studies seldom take both selective pressures and sexes into account. We examined song elaboration and sexual dimorphism in 15 populations of nine fairy-wren species (Maluridae), a Southern Hemisphere clade with female song. We compared song elaboration and sexual song dimorphism to latitude and life history variables tied to sexual and social selection pressures and sex roles. Our results suggest that song elaboration evolved in part due to sexual competition in males: male song variability was more positively correlated with temperate breeding and greater breeding synchrony than female song. We also found strong evidence that sex-role similarity contributed to male-female song similarity: male and female songs were shorter and more similar when parental care was more equal and when male survival was high. Contrary to Northern Hemisphere latitudinal patterns, songs were less dimorphic at higher, temperate latitudes. These results suggest that selection on song can be sex-specific, with male song elaboration favored in contexts coincident with sexual selection. However, selection pressures associated with sex-role similarity also appear to constrain sex specific song evolution and song dimorphism.
Phenotypic integration and developmental canalization have been hypothesized to constrain the degree of phenotypic plasticity, but there is little evidence for the relationships among the three processes in different environments, especially for plants under natural conditions. To address this issue, we conducted a field experiment by subjecting plants of Abutilon theophrasti to low, medium and high densities, under infertile and fertile soil conditions, measured a variety of traits and analyzed canalization (coefficient of variation [CV]), integration (coefficient of integration [CI] and the number of significant correlations of a trait with other traits [NC]), and plasticity (REL RDPIs and ABS RDPIs) in these traits and their relationships at two stages of plant growth. Our results showed an increase in mean CV, NC and ABS RDPIs of traits with density, and the positive correlations between trait NC and ABS RDPIs became stronger with higher densities but weaker over time in fertile soil, while correlations among trait CV, NC and ABS RDPIs became stronger over time in infertile soil. Results suggested shared or cooperation mechanisms among phenotypic integration, canalization and plasticity. Soil conditions and growth stage may affect responses of these correlations to density via modifying plant size and competition strength. The attenuated canalization and enhanced integration may be helpful for the production of plasticity, especially under intense competition.
In general, it is accepted that gap formation significantly affects the placement of scatter-hoarded seeds by small rodents, but the effects of different forest gap sizes on the seed-eating and scatter-hoarding behaviors of small rodents remain unclear. Thus, we examined the effects of a closed canopy forest, forest edge, and gaps with different sizes on the spatial dispersal of Quercus variabilis acorns and cache placement by small rodents using coded plastic tags in the Taihang Mountains, China. The seeds were removed rapidly and there were significant differences in the seed-eating and caching strategies between the stand types. We found that Q. variabilis acorns were usually eaten after being removed from the closed canopy forest and forest edges. By contrast, the Q. variabilis acorns in the forest gap stands were more likely to be scatter hoarded. The dispersal distances of Q. variabilis acorns were significantly longer in the forest gap plots compared with the closed canopy and forest edge plots. However, the proportions of scatter-hoarded seeds did not increase significantly as the gap size increased. In small-scale oak reforestation projects or research, creating small gaps to promote rodent-mediated seed dispersal may effectively accelerate forest recovery and successional processes.
Warning signals are often characterized by highly contrasting, distinctive and memorable colors. Both chromatic (hue) and achromatic (brightness) contrast contribute to signal efficacy, making longwave colored signals (red and yellow) that generate both chromatic and achromatic contrast common. Shortwave colors (blue and ultraviolet) do not contribute to luminance perception, yet are also common in warning signals. The presence of UV aposematic signals is paradoxical as UV perception is not universal, and evidence for its utility is at best mixed. We used visual modeling to quantify how UV affects signal contrast in aposematic butterflies and frogs. We found that UV only appreciably affected visual contrast in the butterflies. As the butterflies, but not the frogs, have UV-sensitive vision these results support the notion that UV reflectance is associated with intraspecific communication, but appears to be non-functional in frogs. Consequently, we should be careful when assigning a selection-based benefit from UV reflectance.
Human–wildlife conflicts have intensified by many folds and at different levels in the recent years. The same is true in the case of the Hindu Kush Himalaya (HKH), the roof of the world and a region known for its wealth in biodiversity. We present systematic literature review (SLR) using the search, appraisal, synthesis, and analysis (SALSA) framework; and for spatial and network analysis, we employed the VOSviewer software. The review – covering 240 peer- articles within a span of 27 years (from 1982 to 2019) – revealed that in the last decade of that period, there was a 57 per cent increase in publications but with disproportionate geographical and thematic focus. About 82 per cent of the research concentrated on protected areas large carnivores and mega herbivores played a big role in such conflicts. About 53 per cent of the studies were based on questionnaires based and the main driver was reported was the habitat disturbance of the animals due to land-cover change, urbanization, and increase in human population. On the management front, the studies reported the use of traditional protection techniques like guarding and fencing. Our analysis of 681 keywords revealed prominent focus on ‘human-wildlife conflict’, ‘Nepal’, ‘Bhutan’, ‘Snow Leopard’ and ‘Leopard’ indicating the issue are linked with these species and countries. The involvement of 640 authors from 36 countries indicates increasing interest and Nepal and India are playing key role from the region. As for the spatial and network analysis that was conducted, while it showed variations in terms of localities, there were conspicuous limitations in terms of having a transboundary focus. Thus, particular attention ought to be paid to building transboundary partnerships and improving management interventions; there is also a pressing need to understand the patterns of human–wildlife convergence, especially involving meso mammals.
Understanding how urbanization alters functional interactions among pollinators and plants is critically important given increasing anthropogenic land use and declines in pollinator populations. Pollinators often exhibit short-term specialization, and visit plants of the same species during one foraging trip. This facilitates plant receipt of conspecific pollen -- pollen on a pollinator that is the same species as the plant on which the pollinator was foraging. Conspecific pollen receipt facilitates plant reproductive success and is thus important to plant and pollinator persistence. We investigated how urbanization affects short term specialization of insect pollinators by examining pollen loads on insects' bodies and identifying the number and species of pollen grains on insects caught in urban habitat fragments and natural areas. We then assessed possible drivers of differences between urban and natural areas, including frequency dependence in foraging, species richness and diversity of the plant and pollinator communities, floral abundance, and the presence of invasive plant species. Pollinators were more specialized in urban fragments than in natural areas, despite no differences in the species richness of plant communities across site types. These differences were likely driven by higher specialization of common pollinators, which were more abundant in urban sites. Pollinators were also more specialized when foraging on invasive plants across sites, and floral abundance of invasive plants was higher in urban sites. Our findings reveal strong effects of urbanization on pollinator fidelity to individual plant species and have implications for the maintenance of plant species diversity in small habitat fragments. The higher fidelity of pollinators to invasive plants suggests that native species may receive fewer visits by pollinators. Therefore, native plant species diversity may decline in urban sites without continued augmentation of urban flora or removal of invasive species.