We sought to assess effect of plant environmental adaptation strategies and evolutionary history and quantify the contribution of ecological processes to community assembly by measuring functional traits and phylogenetic composition in local forest community. We selected 18 dominant tree species in a Lithocarpus glaber–Cyclobalanopsis glauca evergreen broad-leaved forest and measured nine leaf functional traits and phylogenetic data of each species. We analyzed the variation in traits and trade-off relationships, tested phylogenetic effects on leaf functional traits, explored the influence of phylogeny and environment on leaf functional traits, and distinguished the relative effects of spatial and environmental variables on functional traits and phylogenetic compositions. The results showed the following: (i) Leaf traits had moderate intraspecific variation, and significant interspecific variation existed especially among life forms. (ii) Significant phylogenetic signals were detected only in leaf thickness and leaf area. The correlations among traits both supported “the leaf economics spectrum” at the species and community levels, and the relationships significantly increased or only a little change after removing the influence of phylogeny, which showed a lack of consistency between the leaf functional trait patterns and phylogenetic patterns. We infer the coexistent species tended to adopt “realism” to adapt to their habitats. (iii) Soil total potassium and phosphorus content, altitude, aspect, and convexity were the most critical environmental factors affecting functional traits and phylogenetic composition. Total environmental and spatial variables explained 63.38% of the variation in functional trait composition and 47.96% of the variation in phylogenetic structures. Meanwhile, the contribution of pure spatial factors was significantly higher than that of the pure environment. Neutral- theory-based stochastic processes played dominant roles in driving community functional trait assembly, but niche-theory-based determinative processes such as environmental filtering had a stronger effect on shaping community phylogenetic structure at a fine scale.
Ecological traps occur when species choose to settle in lower quality habitats, even if this reduces their survival or productivity. This normally occurs in situations of drastic environmental changes, resulting, for example, from anthropogenic pressures. In the medium and long term, this could mean the extinction of the species. We investigated the dynamics of occurrence and distribution of three canid species (Atelocynus microtis, Cerdocyon thous, and Spheotos venaticus) related to human threats imposed on their habitats in the Amazon Rainforest. We analyzed the possible environmental thresholds for the occurrence of these species and confronted them with the future projections of climatic niches for each one. All three species will be negatively affected by climate change in the future, with losses of up to 91% of the suitable area of occurrence in the Brazilian Amazon. The occurrence of C. thous and S. venaticus has been positively influenced by anthropogenic open areas to the detriment of native environments, suggesting that these species are being attracted by ecological traps, which may put them at risk in the future in the Amazon Region. The A. microtis species is the most dependent on forest habitats, and thus the most significant threat would be forest loss. Using the canid species as a model, we could deeply investigate these ecological effects that can affect a large part of the Amazonian fauna in the current scenario. Considering the high degree of environmental degradation and deforestation in the Amazon Rainforest, the theory of ecological traps must be discussed at the same level that habitat loss is considered a decisive criterion of threat to biodiversity.
In order to interpret the degree of postmating isolation and the evolutionary relationships among Fejervarya species from Indonesia (Lesser Sunda), Bangladesh, China, and Japan, crossing experiments and molecular phylogenetic analyses were carried out using frogs of Fejervarya species from these countries. The crossing experiments revealed that the reciprocal hybrids among F. iskandari, F. verruculosa, and F. sp. Large type, and those between F. multistriata and F. kawamurai were viable through metamorphosis, but those between F. iskandari group and F. limnocharis group were completely or partially inviable at the tadpole stage, and those between Southeast -Asian and South-Asian Fejervarya groups were completely inviable at the embryonic stage. The matured reciprocal hybrids between F. iskandari and F. verruculosa from Indonesia, Lesser Sunda showed some degree of abnormality in spermatogenesis. The phylogenetic analyses using mtDNA Cytb gene sequences demonstrated that F. iskandari formed a sister clade with F. verruculosa from Lesser Sunda, Indonesia with 8.1% sequence divergence. Fejervaraya multistriata from China made a clade with Thailand, Malaysia and Indonesian (topotype) populations of F. limnocharis which showed sister relationships to F. kawamurai from Japan with 8.9% sequence divergence of Cytb gene. Fejervarya sp. small type from Bangladesh formed a clade with the other South-Asian members of Fejervarya group and made a sister clade with Southeast-Asian Fejervarya group having 23.1% sequence divergence of Cytb gene. This study showed that the degree of postmating isolation reflects the molecular phylogenetic relationships, and that the two species, F. iskandari and F. verruculosa from Indonesia (Lesser Sunda) are reproductively isolated by abnormal spermatogenesis, and genetically deviated.
Abstract 1. Elephants frequently raid farmers’ crops within their ranges in Africa and Asia. This can have a large impact on agricultural productivity and food security for farmers. 2. Previous studies have examined susceptibility of crop fields to elephant raids using field characteristics such as field size and proximity to water sources. However, there are limited studies investigating how different crop types, individually and in their combinations influence crop susceptibility to elephant raiding. Also, spatio-temporal patterns in elephant crop raids in agro-ecological landscapes have not been extensively examined. 3. This study utilised data collected from crop fields raided by elephants between 2008 and 2018. Data on crops grown, the number of crop-raiding incidences for each crop, and elephant raiding incidences were recorded for each field assessed. Incidence risks (IR) and field risk value (RV) were computed using an adaptive epidemiological approach. 4. The results showed that elephant crop raiding incidents varied significantly amongst crop types, and over space and time (P<0.0001). Cereal crops (millet: Eleusine conaracana, maize: Zea mays) incurred a higher number of crop raiding incidents compared with leguminous crops (cowpea: Vigna unguiculata; groundnut: Arachis hypogea). Field RVs significantly varied depending on which crop was present in the field. There was a significant negative correlation between the number of crop types and the susceptibility of the field to raiding (R2 = -0.680, P<0.0001). 5. Our results suggest that the susceptibility of the fields to elephant raids could be minimised by selecting crop types and combinations less susceptible to elephant damage, thus enhancing food security for local subsistence farmers. Keywords: crop raiding, crop species, incidence risks, field risk value, food security, human-elephant conflict
Birds provide important ecological services for the maintenance of ecosystems’ integrity. However, there is limited research on ecological roles of different bird species in maintenance of habitats in South Africa yet many bird species are experiencing continuous conservation threats. In this study, we aimed to document the diversity of bird species in South Africa’s Wild Coast nature reserves, and to determine potential role of each bird species in habitat maintenance using bird feeding mode classifications as a species function’s proxy. Bird observations were conducted afield over four years (2017 to 2020). Over 864 hours of field sampling in 2017-2020, we accumulated 818 bird records containing 178 different bird species classified into 58 families. Shannon-Wiener Diversity Indices showed very high overall species diversity, and across the nature reserves (H > 3.5) with however, all nature reserves being non-significantly different. We noted 32 bird species representing 30 families occurring across four nature reserves with Silaka Nature Reserve having significantly more diverse bird families than Mkhambathi Nature Reserve while not significantly different to others. Forest bird species were more dominant (42.1%; N = 178) throughout observations than other habitat species. Annual bird species diversity across the observation years remained very high (H > 3.5) with non-significant differences across the years. However, the year 2018/2019, showed significantly higher abundance of birds across all nature reserves. Among different feeding modes, potential seed dispersers had a significantly greater number of records than other groups while pollinators were not significantly different in number compared to seed predators. A non-significantly different number of birds in medium to large size body size classes suggest availability of a variety of both pollinators and subsequent seed dispersal vectors. Consistent with other studies, conservation status and implications of bird species loss on sustainable vegetation integrity must be prioritised.
Animal-borne telemetry devices provide essential insights into the life-history strategies of far-ranging species and allow us to understand how they interact with their environment. Many species in the seabird family Alcidae undergo a synchronous moult of all primary flight feathers during the non-breeding season, making them flightless and more susceptible to environmental stressors, including severe storms and prey shortages. However, the timing and location of moult remains largely unknown, with most information coming from studies on birds killed by storms or shot at sea. Using light-level geolocators with saltwater immersion loggers, we develop a method for determining flightless periods in the context of the annual cycle. Four Atlantic puffins (Fratercula arctica) were equipped with geolocator/immersion loggers on each leg to attempt to overcome issues of leg-tucking in plumage while sitting on the water, which confounds the interpretation of logger data. Light level and saltwater immersion time-series data were combined to correct for this issue. This approach was adapted and applied to 40 puffins equipped with the standard practice deployments of geolocators on one leg only. Flightless periods consistent with moult were identified in the dual-equipped birds, whereas moult identification in single-equipped birds was less definitive and should be treated with caution. Within the dual-equipped sample, we present evidence for two flightless moult periods per non-breeding season in two puffins that undertook more extensive migrations (> 2000km), and were flightless for up to 76 days in a single non-breeding season. A biannual flight feather moult is highly unusual among non-passerine birds, and may be unique to birds that undergo catastrophic moult, i.e. become flightless when moulting. Though our conclusions are based on a small sample, we have established a freely available methodological framework for future investigation of the moult patterns of this and other seabird species.
1. The encroachment of woody plants into grasslands is an ongoing global problem that is largely attributed to anthropogenic factors such as climate change and land management practices. Determining the mechanisms that drive successful encroachment is a critical step towards planning restoration and long-term management strategies. Feedbacks between soil and aboveground communities can have a large influence on the fitness of plants and must be considered as potentially important drivers for woody encroachment. 2. We conducted a plant-soil feedback experiment in a greenhouse between eastern redcedar Juniperus virginiana and four common North American prairie grass species. We assessed how soils that had been occupied by redcedar, a pervasive woody encroacher in the Great Plains of North America, affected the growth of big bluestem, little bluestem smooth brome, and western wheatgrass over time. We evaluated the effect of redcedar on grass performance by comparing the height and biomass of individuals of each grass species that were grown in live or sterilized conspecific or redcedar soil. 3. We found that redcedar created a negative plant-soil feedback that limited the growth of two species. These effects were found in both live and sterilized redcedar soils, indicating redcedar may exude an allelochemical into the soil that limits grass growth. 4. Synthesis. By evaluating the strength and direction of plant-soil feedbacks in the encroaching range, we can further our understanding of how woody pants successfully establish in new plant communities. Our results demonstrate that plant-soil feedback created by redcedar inhibits the growth of certain grass species. By creating a plant-plant interaction that negatively affects competitors, redcedars increase the probability of seedling survival until they can grow to overtop their neighbors. These results indicate plant-soil feedback is a mechanism of native woody plant encroachment that could be important in many systems yet is understudied.
Workers of the ant Cardiocondyla elegans drop female sexuals into the nest entrance of other colonies to promote outbreeding with unrelated, wingless males. Corroborating results from previous years we document that carrier and carried female sexuals are typically related and that the transfer initially occurs mostly from their joint natal colonies to unrelated colonies. Female sexuals mate multiply with up to seven genetically distinguishable males. Contrary to our expectation, the colony growth rate of multiple-mated and outbred female sexuals was lower than that of inbred or single-mated females, leading to the question of why female sexuals mate multiply at all. Despite the obvious costs, multiple mating might be a way for female sexuals to “pay rent” for hibernation in an alien nest. We argue that in addition to evading inbreeding depression from regular sibling mating over many generations, assisted dispersal might also be a strategy for minimizing the risk of losing all reproductive investment when nests are flooded in winter.
Aim: Understand the ecological processes that shape community composition in eelgrass meadows along the coast of France at local and regional scales. Location: Northeastern Atlantic. Methods: Combining taxonomic and trait-based approaches with structural equation modeling, we explored the mechanisms governing community assembly in five meadows located over a distance of 800 km along the French coast in the Northeast Atlantic. We assessed the spatial variability of eelgrass-associated invertebrate communities as affected by environmental parameters or morphological traits of the eelgrass and linked these mechanisms to their impacts at local and regional scales through analyses of the taxonomic and functional α and β diversities. We then quantified the direct and indirect effects of environmental factors on macrofaunal structure and composition. Results: Eelgrass meadows locally favored higher species abundance, diversity, and functional traits present in the community relative to nearby bare sediments. At the regional scale, eelgrass diversity was comparable between sites, with high species turnover observed among them, and each site being characterized by different species and different sets of traits. These differences were due in part to morphological traits of the meadows, but the explanatory variables that best explained the differences among the meadows were environmental conditions, including temperature, current velocity, and Δ water level. Main conclusions: Meadows appear to harbor subsets of species from the regional species pool, rather than harboring eelgrass-specific assemblages. The processes that maintain seagrass diversity appear to reflect a seascape-scale meta-community composed of many habitats connected by source-sink dynamics. Given that eelgrass enhances the diversity and abundance of species found in neighboring habitats, conservation programs should consider ecosystem-level protection spanning multiple habitats, including eelgrass, in order to maximize the protection of biodiversity.
One of the most effective defenses of avian hosts against obligate brood parasites is the ejection of parasitic eggs from the nests. Despite the clear fitness benefits of this behavior, individuals within so-called “egg rejecter” host species still show substantial variation in their propensity to eliminate foreign eggs from the nest. We argue that this variation can be further understood by studying the physiological mechanisms of host responses to brood parasitic egg stimuli: independent lines of research increasingly support the hypothesis that stress-related physiological response to parasitic eggs may trigger egg rejection. The “stress-mediated egg rejection” hypothesis requires that hosts activate the stress-response when responding to parasitic eggs. We tested this prediction by experimentally parasitizing incubating American robins Turdus migratorius, an egg rejecter host to obligate brood parasitic brown-headed cowbirds Molothrus ater, with mimetic or non-mimetic model eggs. To assess the stress response, we measured the heart rate in incubating females immediately after experimental parasitism. We also measured plasma corticosterone and, in a subset of birds, used RNA-sequencing to analyze the expression of proopiomelanocortin (POMC), a precursor of adrenocorticotropic hormone (ACTH), two hours after experimental parasitism. We found that egg type had no effect on heart rate. Two hours following experimental parasitism, plasma corticosterone did not differ between the differently colored model egg treatments or between rejecter and accepter females within the non-mimetic treatment. However, females exposed to non-mimetic eggs showed an upregulation of POMC gene expression in the pituitary compared to females treated with mimetic eggs. Our findings suggest that parasitic eggs may activate the stress-related hypothalamic-pituitary-adrenal axis in an egg-rejecter host species, although the dynamics of this response are not yet understood.
Uganda lies within the drier end of the natural distribution range of Coffea canephora and contains unexplored genetic material that could be drought-adapted and useful for developing climate-resilient varieties. Using experimental treatments, (i) ample and (ii) restricted-water, response of 148 genotypes were studied comprising wild, feral and cultivated C. canephora. Biomass allocation, standing leaf area and leaf area growth data were collected. Linear mixed effect models and PCA were used to analyse effect of drought on genotypes from different: (i) cultivation status, (ii) genetic groups and (iii) locations. We assessed the relationship between drought tolerance for relative growth rate in leaf area (RGRA), total number of leaves (TNL), total leaf area (TL) and total leaf dry weight (TLDW) of genotypes at final harvest. Restricted-water reduced RGRA across genetic groups (3.2 – 32.5%) and locations (7.1 – 36.7%) but not cultivation status. For TNL, TL and TLDW, genotypes that performed well in ample-water performed worse under restricted-water, indicating growth-tolerance trade-off. Drought tolerance in RGRA and TNL were negatively correlated with wetness index suggesting some degree of adaptation to local climate. Findings indicate a growth-tolerance trade-off within this tropical tree species and drought tolerance of Uganda’s C. canephora is somewhat associated with local climate.
Allopreening occurs in many species of birds and is known for providing hygienic and social benefits. While this behavior has been studied between conspecifics, its occurrence among different species remains mysterious. Outside of captive environment, only a few records of interspecific allopreening exist. In this study, we describe our observations of Spot-necked Babbler (Stachyris strialata) preening Nonggang Babbler (Stachyris nonggangensis) in a non-captive environment in southern China. We provide three hypotheses (social dominance, cleaning mutualism, and hybridization) to explain the occurrence of this understudied behavior. We suggest that interspecific allopreening may not be as rare as we thought if we study this behavior under circumstances where it most frequently occurs. This study contributes to our understanding of not only the potential mechanism(s) for interspecific allopreening but also the behavioral ecology of the vulnerable Nonggang Babbler.
Cost-effective use of limited conservation resources requires understanding which data can most contribute to alleviating biodiversity declines. Interventions might reasonably prioritise life-cycle transitions with the greatest influence on population dynamics, yet some contributing vital rates are particularly challenging to document; such pragmatic decision-making risks suboptimal management if less is known about influential rates. We aimed to explore whether study effort aligns with demographic impact on population growth rate, λ. We parameterised a matrix population model using meta-analysis of vital rates for the common eider (Somateria mollissima), an increasingly threatened yet comparatively data-rich species of seaduck. Female common eiders exhibit intermittent breeding, with some established breeders skipping one or more years between breeding attempts. We accounted for this behaviour by building breeding propensity (= 0.72) into our model with a discrete and reversible ‘non-breeder’ stage (to which surviving adults transition with a probability of 0.28). The transitions between breeding and non-breeding states had twice the influence on λ than fertility (summed matrix-element elasticities of 24% and 11%, respectively), whereas almost 15 times as many studies document components of fertility than breeding propensity (n = 103 and n = 7, respectively). Through comparative re-analyses, we find similar results for two amphibian species, further supporting our finding that study effort does not always occur in proportion to relative influence on λ. Our workflow could form part of the toolkit informing future investment of finite resources, to avoid repeated disconnects between data needs and availability thwarting evidence-driven conservation.
Giant clams are ecologically important, benefitting species of all trophic levels. But numerous populations have declined drastically in numbers due to past intensive exploitation that led to their listing in both CITES Appendix II and IUCN Red List of Threatened Species.. However, giant clams are notoriously difficult to identify, and recent molecular work has revealed that morphological misidentification of giant clams have confounded current population assessments and extinction risk. The most recent study of the status of giant clams in the Samoan Archipelago was published in a journal over 20 years ago, without molecular corroboration of visual identifications. Using morphologic characteristics and ezRAD genetic techniques, we identify the existence of Tridacna noae in the Samoan Archipelago, presenting the first observation and a resulting range expansion. Accurately identifying the extant species in the archipelago is the first step towards a much-needed population status assessment to effectively manage these long-lived species.
Intense fishing pressure and climate change are major threats to fish populations and coastal fisheries. Larimichthys crocea (large yellow croaker) is a long-lived fish, which performs seasonal migrations from its spawning and nursery grounds along the coast of the East China Sea (ECS) to overwintering grounds offshore. This study used length-based analysis and habitat suitability index (HSI) model to evaluate current life-history parameters and overwintering habitat suitability of L. crocea, respectively. We compared recent (2019) and historical (1971-1982) life-history parameters and overwintering HSI to analyze the fishing pressure and climate change effects on the overall population and overwintering phase of L. crocea. The length-based analysis indicated serious overfishing of L. crocea, characterized by reduced catch yield, size truncation, constrained distribution, and advanced maturation causing a recruitment bottleneck. The overwintering HSI modeling results indicated that climate change has led to decreased sea surface temperature during L. crocea overwintering phase over the last half-century, which in turn led to area decrease and an offshore-oriented shifting of optimal overwintering habitat of L. crocea. The fishing-caused size truncation may have constrained the migratory ability and distribution of L. crocea subsequently leading to the mismatch of the optimal overwintering habitat against climate change background, namely habitat bottleneck. Hence, while heavily fishing was the major cause of L. crocea collapse, climate-induced overwintering habitat suitability may have intensified the fishery collapse of L. crocea population. It is important for management to take both overfishing and climate change issues into consideration when developing stock enhancement activities and policy regulations, particularly for migratory long-lived fish that share a similar life history to L. crocea. Combined with China’s current restocking and stock enhancement initiatives, we propose recommendations for future restocking of L. crocea in China.
Parasites form an integral part of food webs, however, mechanistic insights into the role of parasites for energy flow and community dynamics is currently limited by a lack of conceptual studies investigating host-parasite interactions in a community context. In aquatic systems, chytrids constitute a major group of fungal parasites and their free-living infective stage (zoospores) forms a highly nutritional food source to zooplankton. Consumption of zoospores can create an energy pathway from otherwise inedible phytoplankton to zooplankton (“mycoloop”). The impact of such parasite-mediated energy pathways on community dynamics and energy transfer to higher trophic levels is of high importance considering eutrophication and global warming induced shifts to dominance of unfavourable prey such as cyanobacteria. We theoretically investigated community dynamics and energy transfer in a food web consisting of an edible-nonhost and an inedible-host phytoplankton species, a fungal parasite, and a zooplankton species grazing on edible phytoplankton and fungi. Food web dynamics were investigated along a nutrient gradient for two cases: (1) non-adaptive zooplankton species representative for filter feeders like cladocerans and (2) zooplankton with the ability to actively adapt their feeding preferences like many copepod species. For both feeding strategies, the importance of the mycoloop for zooplankton increases with nutrient availability. This increase is smooth for non-adaptive consumers. For a consumer with an adaptive feeding preference, we observe an abrupt shift from almost exclusive preference for edible phytoplankton (dominant prey) at low nutrient levels to a strong preference for parasitic fungi at high nutrient levels. The model predicts that parasitic fungi can contribute up to 50% of the zooplankton diet in nutrient rich environments, agreeing with empirical observations on zooplankton gut content from eutrophic systems during cyanobacterial blooms. Our findings highlight the role of parasite-mediated energy pathway for predictions on energy flow and community composition under environmental change.
1. Bumble bees are key pollinators with some species reared in captivity at a commercial scale, but with evidence of population declines and with alarming predictions under climate change scenarios. While studies on the thermal biology of temperate species are still limited, they are entirely absent from the tropics where the effects of climate change are expected to be greater. 2. Herein we test if tropical bumble bees’ lower (CTMin) and upper (CTMax) critical thermal limits decrease with elevation and if the stable optimal conditions used in laboratory-reared colonies reduces their thermal tolerance. 3. We assessed changes in CTMin and CTMax of four species at two elevations (2600 and 3600 m) in the Colombian Andes and of laboratory-reared individuals of B. pauloensis. In addition, we examined the effect of body size and compiled information on bumble bees’ thermal limits from the literature to assess potential predictors for broad-scale patterns of variation. 4. CTMin decreased with elevation while CTMax did not. CTMax was slightly higher (0.84 °C) in laboratory-reared than in wild-caught bees while CTMin was similar. CTMin decreased with increasing body size while CTMax did not. Latitude is a good predictor for variations in CTMin while annual mean temperature and extreme monthly temperatures are good predictors for both CTMin and CTMax. 5. The stronger response in CTMin with increasing elevation supports Brett’s heat-invariant hypothesis. Tropical bumble bees appear to be about as heat tolerant as those from temperate areas, suggesting that other aspects of climate besides temperature (e.g., water balance) might be more determinant environmental factors for these species under global warming. Laboratory-reared colonies are adequate surrogates for addressing questions on thermal tolerance and global warming impacts.
Patterns of biodiversity provide insights into the processes that shape biological communities around the world. Variation in species diversity along biogeographical or ecological gradients, such as latitude or precipitation, can be attributed to variation in different components of biodiversity: changes in the total abundance (i.e. more-individual effects) and changes in the regional species abundance distribution (SAD). Rarefaction curves can provide a tool to partition these sources of variation on diversity, but first must be converted to a common unit of measurement. Here, we partition species diversity gradients into components of the SAD and abundance using the effective number of species (ENS) transformation of the individual-based rarefaction curve. Because the ENS curve is unconstrained by sample size, it can act as a standardized unit of measurement when comparing effect sizes among different components of biodiversity change. We illustrate the utility of the approach using two datasets spanning latitudinal diversity gradients in trees and marine reef fish, and find contrasting results. Whereas the diversity gradient of fish was mostly associated with variation in abundance (86%), the tree diversity gradient was mostly associated with variation in the SAD (59%). These results suggest that local fish diversity may be limited by energy through the more-individuals effect, while species pool effects are the larger determinant of tree diversity. We suggest that the framework of the ENS-curve has the potential to quantify the underlying factors influencing most aspects of diversity change.