The neurotransmitter dopamine has been shown to play an important role in modulating behavioural, morphological and life-history responses to food abundance. However, costs of expressing high dopamine levels remain poorly studied and are essential for understanding the evolution of the dopamine system. Negative maternal effects on offspring size from enhanced maternal dopamine levels have previously been documented in Daphnia. Here, we tested whether this translates into fitness costs in terms of lower starvation resistance in offspring. We exposed Daphnia magna mothers to aqueous dopamine (2.3 mg/L or 0 mg/L for the control) at two food levels (ad libitum versus 30% ad libitum) and recorded a range of maternal life history traits. The longevity of their offspring was then quantified in the absence of food. In both control and dopamine treatments, mothers that experienced restricted food ration had lower somatic growth rates and higher age at maturation. Maternal food restriction also resulted in production of larger offspring that had a superior starvation resistance, compared to ad libitum groups. However, although dopamine exposed mothers produced smaller offspring than controls at restricted food ration, these smaller offspring survived longer under starvation. Hence, maternal dopamine exposure provided an improved offspring starvation resistance. We discuss the relative importance of proximate and ultimate causes for why D. magna may not evolve towards higher endogenous dopamine levels despite the fitness benefits this appears to have.
Phytoplankton functional traits can represent particular environmental conditions in complex aquatic ecosystems. Categorizing phytoplankton species into functional groups is challenging and time-consuming, and requires high-level expertise on species autecology. In this study, we introduced an affinity analysis to aid identification of candidate associations of phytoplankton from two datasets comprised of phytoplankton and environmental information. In the Huaihe River Basin with a drainage area of 270,000 km2 in China, samples were collected from 217 selected sites during the low-water period in May 2013; monthly samples were collected during 2006-2011 in a man-made pond, Dishui Lake. Our results indicated that the affinity analysis can be used to define some meaningful functional groups. The identified phytoplankton associations reflect the ecological preferences of phytoplankton in terms of light and nutrients acquisition. Advantages and disadvantages of applying the affinity analysis to identify phytoplankton associations are discussed with perspectives of their utility in ecological assessment.
Theoretical modelling predicts that both direct and delayed density-dependence are key factors to generate population cycles. Deciphering density-dependent processes that lead to variable population growth characterizing different phases of the cycles remain challenging. This is particularly the case for the period of prolonged low densities, which is inherently data deficient. However, demographic analyses based on long-term capture-mark-recapture datasets can help resolve this question. We relied on a 16-yr (2004-2019) live-trapping program to analyse the summer demography and movements of a cyclic brown lemming population in the Canadian Arctic. More specifically, we examined if inversely density-dependent processes could explain why population growth can remain low during the prolonged low phase. We found that the proportion of females in the population was inversely density-dependent with a strong male-biased sex ratio at low densities but not at high densities. However, survival of adult females was higher than adult males, but both had lower survival at low densities than at high ones. Distances moved by both adult males and females were density-dependent, and proportion of females in reproductive condition was weakly density-dependent as it tended to increase at low density. Individual body condition, measured as monthly change in body mass, was not density-dependent. Overall, the strong male-biased sex ratio at very low densities suggests a loss of reproductive potential due to the rarity of females and appears to be the most susceptible demographic factor that could contribute to the prolonged low phase in cyclic brown lemmings. What leads to this sex-bias in the first place is still unclear, potentially owing to our trapping period limited to the summer, but we suggest that it could be due to high predations rate on breeding females in winter.
1. Cattle grazing profoundly affects abiotic and biotic characteristics of ecosystems. While most research has been performed on grasslands, the effect of large managed ungulates on forest ecosystems has largely been neglected. 2. Compared to a baseline semi-natural state, we investigated how long-term cattle grazing of birch forest patches affected the abiotic state and the ecological community (microbes and invertebrates) of the soil subsystem. 3. Grazing strongly modified the soil abiotic environment by increasing phosphorus content, pH and bulk density, while reducing the C:N ratio. The reduced C:N-ratio was strongly associated with a lower microbial biomass, mainly caused by a reduction of fungal biomass. This was linked to a decrease in fungivorous nematode abundance and the nematode channel index, indicating a relative uplift in the importance of the bacterial energy-channel in the nematode assemblages. 4. Cattle grazing highly modified invertebrate community composition producing distinct assemblages from the semi-natural situation. Richness and abundance of microarthropods was consistently reduced by grazing (excepting collembolan richness) and grazing-associated changes in soil pH, Olsen P and reduced soil pore volume (bulk density) limiting niche space and refuge from physical disturbance. Anecic earthworm species predominated in grazed patches, but were absent from ungrazed forest, and may benefit from manure inputs, while their deep vertical burrowing behaviour protects them from physical disturbance. 5. Perturbation of birch forest habitat by long-term ungulate grazing profoundly modified soil biodiversity, either directly through increased physical disturbance and manure input or indirectly by modifying soil abiotic conditions. Comparative analyses revealed the ecosystem engineering potential of large ungulate grazers in forest systems through major shifts in the composition and structure of microbial and invertebrate assemblages, including the potential for reduced energy flow through the fungal decomposition pathway. The precise consequences for trophic interactions and biodiversity-ecosystem function relationships remains to be established, however.
The biodiversity in mountainous ecosystems is high but is threatened by rapid environmental change. Urbanization and other anthropogenic factors in the mountains surrounding cities can affect land use and spatial fragmentation. Moreover, patterns of habitat are closely related to elevation and have a major effect on montane biodiversity. The aim of this study was to analyze the effects of spatial fragmentation on the vertical distribution pattern of bird diversity by characterizing the structure of the bird community, species diversity, and landscape factors at different altitudes. From 2016 to 2019, this study made a four-years continuous monitoring of the breeding biric belts. The result indicated Mount Tai harbored a high bird diversity. Bird richness, abundance and Shannon-Wiener index decreased with latitude in Mount Tai. Moreover, the composition of bird communities varied along altitudinal gradients and supported some special species in different elevational bands. Road density, number of habitat patches, patch density, and the percentage of forest significantly affected bird diversity. The effect of patch density was higher compared with other landscape factors. Sufficient habitat and more patches in the low-mountain belt supported higher bird diversity. The middle-mountain belt and high-mountain belt showed contrasting patterns. Our results highlight the effects of ongoing urbanization and human activities on montane biodiversity and emphasize the need for artificial habitats in the mountains surrounding cities to be managed.
The relationships among species diversity, functional diversity, functional redundancy, and community stability are central to community and ecosystem ecology. This paper examines plant communities at different stages of vegetation restoration in the Guizhou karst plateau to study the relationship among functional diversity, functional redundancy, and stability of plant communities. The most important results include the following. (1) Species diversity (SD), functional redundancy (FR), and stability (STB) gradually increased with restoration, and there were significant differences among the different stages; functional diversity (FD) increased at first and then decreased, and reached the highest level at the tree irrigation stage. (2) Plant height (PLH) and specific leaf area (SLA) were functional traits that affected the diversity and stability of the plant community, and PLH was positively correlated with plant community diversity and stability, while SLA was negatively correlated with plant community diversity and stability. (3) During the community recovery, FD and FR interacted to maintain stability. In the early and late stages of recovery, the effect of functional redundancy on stability was greater than that of functional diversity, but it was the opposite in the middle stages. (4) The tree irrigation stage is the likely point at which the species diversity of plant communities in karst areas reached saturation, and the growth rate of functional redundancy after species diversity saturation was greater than that before saturation.
Ecological models are extensively and increasingly used in support of environmental policy and decision making. Dynamic Bayesian Networks (DBN) as a tool for conservation have been demonstrated to be a valuable tool for providing a systematic and intuitive approach to integrating data and other critical information to help guide the decision-making process. However, data for a new ecosystem are often sparse. In this case, a general DBN developed for similar ecosystems could be applicable, but this may require the adaptation of key elements of the network. The research presented in this paper focused on a case study to identify and implement guidelines for model adaptation. We adapted a general DBN of a seagrass ecosystem to a new location where nodes were similar, but the conditional probability tables varied. We focused on two species of seagrass (Zostera noltei and Z. marina) located in Arcachon Bay, France. Expert knowledge was used to complement peer-reviewed literature to identify which components needed adjustment including parameterisation and quantification of the model and desired outcomes. We adopted both linguistic labels and scenario-based elicitation to elicit from experts the conditional probabilities used to quantify the DBN. Following the proposed guidelines, the model structure of the DBN was retained, but the conditional probability tables were adapted for nodes that characterised the growth dynamics in Zostera spp. population located in Arcachon Bay, as well as the seasonal variation on their reproduction. Particular attention was paid to the light variable as it is a crucial driver of growth and physiology for seagrasses. Our guidelines provide a way to adapt a general DBN to specific ecosystems to maximise model reuse and minimise re-development effort. Especially important from a transferability perspective are guidelines for ecosystems with limited data, and how simulation and prior predictive approaches can be used in these contexts.
Indiscriminate fire is rampant throughout subtropical South and Southeast Asian grasslands. However, very little is known about the role of fire and pyric herbivory on the functioning of highly productive subtropical monsoon grasslands lying within Cwa-climatic region. We collected grass samples from 60 m x 60 m plots and determined vegetation physical and chemical properties at regular 30-day intervals from April to July 2020, starting from 30 days after fire to assess post-fire regrowth forage quality. We counted pellet groups for the same four months from 2 m x 2 m quadrats that were permanently marked with pegs along the diagonal of each 60 m x 60 m plot to estimate grazing intensity to the progression of post-fire regrowth. We observed strong and significant reductions in crude protein (mean value 9.1 to 4.1 [55% decrease]) and phosphorus (mean value 0.2 to 0.11 [45% decrease]) in forage collected during different time intervals i.e., from 30 days to 120 days after fire. Mesofaunal deer utilised the burned areas extensively for a short period, i.e., up to two months after fire when the burned areas contained short grasses with a higher level of crude protein and phosphorus. Grazing intensity of chital (Axis axis) to post-fire regrowth differed significantly over time since fire, with higher intensity of use at 30 days after fire. Grazing intensity of swamp deer (Rucervus duvaucelii) did not differ significantly until 90 days after fire, however, decreased significantly after 90 days since fire. Large-scale indiscriminate single event fires thus may not fulfil nutritional requirements of all species in mesofaunal deer community in these subtropical monsoon grasslands. We recommend for a spatio-temporal manipulation of fire to reinforce grazing feedback and to yield for the longest possible period a reasonably good food supply for the conservation of mesofaunal deer.
Molluscs are an important component of the mangrove ecosystem, and the vertical distributions of molluscan species in this ecosystem are primarily dictated by tidal inundation. Thus, sea-level rise (SLR) may have profound effects on mangrove mollusc communities. Here, we used two dynamic empirical models based on measurements of surface elevation change, sediment accretion and zonation patterns of molluscs to predict changes in molluscan spatial distributions in response to different sea-level rise rates in the mangrove forests of Zhenzhu Bay (Guangxi, China). The change in surface elevation was 4.76–9.61 mm a−1 during the study period (2016–2020), and the magnitude of surface-elevation change decreased exponentially as original surface elevation increased. Based on our model results, we predicted that mangrove molluscs might successfully adapt to a low rate of SLR (marker-horizon model: 2–4.57 mm a−1; plate model: 2–5.20 mm a−1) by 2100, with molluscs moving seaward and those in the lower intertidal zones expanding into newly available zones. However, as SLR rate increased (marker-horizon model: 4.57–8.14 mm a−1; plate model: 5.20–6.88 mm a−1), our models predicted that surface elevations would decrease beginning in the high intertidal zones and gradually spreading to the low intertidal zones. Finally, at high rates of SLR (marker-horizon model: 8.14–16.00 mm a−1; plate model: 6.88–16.00 mm a−1), surface elevations were predicted to decrease across the elevation gradient, with molluscs moving landward and species in higher intertidal zones would be blocked by landward barriers. Tidal inundation and the consequent increase in interspecific competition and predation pressure were predicted to threaten the survival of many molluscan groups in higher intertidal zones, especially species at the landward edge of the mangroves. Thus, future efforts to conserve mangrove floral and faunal diversity should prioritize species restricted to landward mangrove areas.
In this study, the plant communities at five succession stages (herbage, herbage-shrub, shrub, tree-shrub, and tree) in the Zhenning Karst Plateau area of Guizhou were examined. The changes of plant functional characteristics in different succession stages were analyzed, as was the relationship between functional traits and environmental factors. The main results include the following. (1) During the succes-sion process, plant height, leaf dry matter mass, leaf area, leaf nitrogen content, and leaf phosphorus content gradually increased, whereas leaf thickness and specific leaf area decreased, and leaf C:P ratio and leaf N:P ratios did not change significantly. (2) Soil organic matter, soil total nitrogen, soil total phosphorus, soil C:N, soil C:P, and soil C:K increased at first and then decreased, reaching a peak at the tree-shrub stage. Soil total potassium fluctuated and soil bulk density gradually decreased and reached the lowest value at the tree-shrub stage. (3) Redundancy analysis (RDA) showed that the plant community shifted from a nutri-ent-poor soil environment to a nutrient-rich environment. Soil total phosphorus, soil C:K, soil organic mat-ter, soil C:N, and soil bulk density were the key environmental factors affecting the change of functional traits. (4) Structural equation modeling suggests that that specific leaf area and leaf nitrogen content had more sensitive responses to soil nutrient resources and environmental factors, respectively.
In many cases, understanding species level responses to climate change requires understanding variation among individuals in response to such change. For species with strong symbiotic relationships, such as many coral reef species, genetic variation in symbiont responses to temperature may affect the response to increased ocean temperatures. To assess variation among symbiont genotypes, we examined the population dynamics and physiological responses of genotypes of Breviolum antillogorgium in response to increased temperature. We found broad temperature tolerance across genotypes, with all genotypes showing positive growth at 26, 30, and 32 C. Genotypes differed in the magnitude of the response of growth rate and carrying capacity to increasing temperature, suggesting that natural selection could favor different genotypes at different temperatures. However, the historical temperature at which genotypes were reared was not a good predictor of temperature response, suggesting a lack of adaptation to temperature over hundreds of generations. We found increased photosynthetic rates and decreased respiration rates with increasing temperature, and differences in physiology among genotypes, but found no significant differences in the response of different genotypes to temperature. In species with such broad thermal tolerance, selection experiments on symbionts outside of the host may not yield results sufficient for evolutionary rescue from climate change.
Play behavior is a significant trait of immature nonhuman primates (hereafter primates), which may play important roles in sensory, locomotor, socio-cognitive, and developmental processes in primates. It has been suggested that function of play is to practice and improve motor skills related to foraging, avoiding predation, attracting mates, raising offspring, and also is to strength social skills concerning to cementing friendly relationships and defraying aggression among individuals. From September 2009 to August 2010, we investigated play behaviors of 1-12-month-old white-headed langur (Trachypithecus leucocephalus) which is a critically endangered primate endemic to China. During this study, we recorded 4,421 play bouts and 1,302 minutes of play time of 7 infants in total. We found that infants had different play behavior patterns at different ages. Specifically, non-social play behaviors appeared at 1 month of age, social play behaviors at 2 months, and all types of social and non-social play behaviors at 3 months. The frequency and duration of non-social play peaked at 5 months and then decreased, while social play appeared at 2 months and gradually increased with age. Non-social play did not differ between the sexes, whereas social play showed sex specificity, with higher frequency and duration of social play in male infants than in female infants. In addition, male and female white-headed langur infants appeared to prefer the individuals of same sex as social playmates. In conclusion, we first reported the pattern of play behavior of a critically endangered langur aged 1 to 12 months though the sample size is small, our results suggest they may have the adaptation of play behaviors in ages and sexes, which may help them adapt to their habitat and social system.
Gut microbiome is vertically transmitted by maternal lactation at birth in mammals. In this study, we investigated the gut microbiome and diet compositions of muskox, a large herbivore in the high Arctic. From muskox feces in Ella Island, East Greenland, we compared the microbiota composition using bacterial 16S rRNA gene sequencing and the dietary compositions of six female adults and four calves have been compared. Firmicutes was the most abundant bacterial phylum in both adults and calves, comprising 94.36% and 94.03%, respectively. There were significant differences in the relative abundance of two Firmicutes families: the adults were mainly dominated by Ruminococcaceae (73.90%), while the calves were dominated by both Ruminococcaceae (56.25%) and Lachnospiraceae (24.00%). Stable isotope analysis on the feces and eight referential plant samples in the study area showed that both adults and calves had similar ranges of 13C and 15N, possibly derived from the dominant diet plants of Empetrum nigrum and Salix glauca. Despite the similar diets, the different gut microbiome compositions in muskox adults and calves indicate that the gut microbiome of the calves may not be fully colonized yet as much as the one of the adults.
1.Herbaceous aboveground biomass (HAB) is a key indicator of grassland vegetation and indirect estimation tools, such as remote sensing imagery, increase the potential for covering larger areas in a timely and cost-efficient way. Structure from motion (SfM) is an image analysis process that can create a 3D model from a set of images. 2: Computed from UAV and ground camera measurements, the SfM potential to estimate the herbaceous aboveground biomass in Sahelian rangelands was tested in this study. Both UAV and ground camera recordings were used at three different scales: temporal, landscape and national (across Senegal). All images were processed using PIX4D software and were used to extract vegetation indices and heights. 3: A random forest algorithm was used to estimate the HAB and the average estimation errors were around 150 g.m-² for fresh mass (20% relative error) and 60 g.m-² for dry mass (around 25% error). A comparison between different datasets revealed that the estimates based on camera data were slightly more accurate than those from UAV data. 4:It was also found that combining datasets across scales for the same type of tool (UAV or camera) could be a useful option for monitoring HAB in Sahelian rangelands or in other grassy ecosystem.
Methods for long-term monitoring of coastal species such as harbor seals, are often costly, time-consuming, and highly invasive, underscoring the need for improved techniques for data collection and analysis. Here, we propose the use of automated facial recognition technology for identification of individual seals and demonstrate its utility in ecological and population studies. We created a software package, SealNet, that automates photo identification of seals, using a graphical user interface (GUI) software to identify, align and chip seal faces from photographs and a deep convolutional neural network (CNN) suitable for small datasets (e.g., 100 seals with five photos per seal). We piloted the SealNet technology with a population of harbor seals located within Casco Bay on the coast of Maine, USA. Across two-years of sampling, 2019 and 2020, at seven haul-out sites in Middle Bay, we processed 1529 images representing 408 individual seals and achieved 88% (93%) rank-1 accuracy in closed set (open set) seal identification. We identified four seals that were photographed in both years at neighboring haul-out sites, suggesting that some harbor seals exhibit site fidelity within local bays across years, and that there may be evidence of spatial connectivity among haul-out sites. Using capture-mark-recapture (CMR) calculations, we obtained a rough preliminary population estimate of 4386 seals in the Middle Bay area. SealNet software outperformed a similar face recognition method developed for primates, PrimNet, in identifying seals following training on our seal dataset. The ease and wealth of image data that can be processed using SealNet software contributes a vital tool for ecological and behavioral studies of marine mammals in the emerging field of conservation technology.
1. For many elusive insect species, which are difficult to cover by standard monitoring schemes, innovative monitoring methods are needed to gain robust data on population trends. We suggest a monitoring of overwintering larvae for the endangered nymphalid butterfly Limenitis reducta. 2. We tested one removal and three detection-mark-redetection (DMR) approaches in a field study in the “Alb-Donau” region, Germany. We replaced movement of the study organisms by random movement of multiple different surveyors, and we examined the model assumption of equal detectability using simulations. 3. Our results indicate that multi-surveyor removal/DMR techniques are suitable for estimating abundance of overwintering L. reducta larvae. Detection probabilities varied with surveyor experience and the uncertainty of population estimates increased with a decrease in personnel expenditure. Estimated larval densities on a spruce clear-cut ranged between one and three individuals per 100 m². 4. We suggest a detection-mark-redetection (DMR) approach with three trained surveyors for the monitoring of L. reducta populations in the pre-imaginal stage. Besides L. reducta, the proposed method is likely to be suitable for other insect taxa with specific immobile life-stages and some sessile organisms, e.g. corals, elusive plants, or fungi.
The genus Phyllachora contains numerous obligate fungal parasites that produce raised, melanized structures called stromata on their plant hosts referred to as tar spot. Members of this genus are known to infect many grass species but generally do not cause significant damage or defoliation, with the exception of P. maydis which has emerged as an important pathogen of maize throughout the Americas, but the origin of this pathogen remains unknown. To date, species designations for Phyllachora have been based on host associations and morphology, and most species are assumed to be host specific. We assessed the sequence diversity of 186 single stroma isolates collected from 16 hosts representing 15 countries. Samples included both herbarium and contemporary strains that covered a temporal range from 1905-2019. These 186 isolates were grouped into 5 distinct species with strong bootstrap support. We found three closely related, but genetically distinct groups of Phyllachora are capable of infecting maize in the United States, we refer to these as the P. maydis species complex. Based on herbarium species, we hypothesize that these three groups in the P. maydis species complex originated from Central America, Mexico and the Caribbean. Although two of these groups were only found on maize, the third and largest group contained contemporary strains found on maize and other grass hosts, as well as herbarium specimens from maize and other grasses that include 10 species of Phyllachora. The herbarium specimens were identified based on morphology and host association, but our sequence data indicates some Phyllachora species are capable of infecting a broad range of host species and there may be significant synonymy in the Phyllachora genus and additional work on species delineation and host specificity should be considered.
Duckweeds (Lemnaceae) are increasingly studied for their potential for phytoremediation of heavy-metal polluted water bodies. A prerequisite for metal removal, however, is the tolerance of the organism to the pollutant, e.g., the metal zinc (Zn). Duckweeds have been shown to differ in their tolerances to Zn, however, despite them most commonly co-occurring with other species, there is a lack of research concerning the effect of species interactions on Zn tolerance. Here we tested whether the presence of a second species influenced the growth rate of the three duckweed species Lemna minor, Lemna gibba, and Lemna turionifera. We used four different Zn concentrations in a replicated microcosm experiment under sterile conditions, either growing the species in isolation or in a 2-species mixture. The response to Zn differed between species, but all three species showed a high tolerance to Zn, with low levels of Zn even increasing the growth rates. The growth rates of the individual species were influenced by the identity of the competing species, but this was independent of the Zn concentration. Our results suggest that species interactions should be considered in future research with duckweeds and that several duckweed species have high tolerance to metal pollution, making them candidates for phytoremediation efforts.