1. Omnivores utilise dietary sources which differ in nutrients, hence dietary restrictions due to environmental change or habitat alteration should cause nutrient limitations; and thus, deterioration of body condition if omnivory is obligate. 2. We investigated how the body condition of the Village weaver Ploceus cucullatus (weavers), which forages predominantly on grains, responds to insects and fruits deprivation. 3. Forty wild-caught weavers held in aviaries were fed a combination of grains and fruits, or grains and insects ad libitum for eight weeks. We confirmed diet preference by recording the number of foragers on each diet option per minute for one hour and the amount of food left-over after 3 hours of foraging. Fortnightly, we assessed indices of body condition including body mass, pectoral muscle, and fat scores, Packed Cell Volume (PCV) and Haemoglobin Concentration (HBC). We modelled the number of foragers, food left-over and body condition as functions of diet, while accounting for time (weeks) and sex effects. 4. We confirmed grains as the preferred diet and found that males ate more fruits and insects than females. Weavers fed on grains and fruits lost body and pectoral muscle mass and accumulated less fat than those fed on grains and insects. This effect was sex-dependent: females deprived of insects lost more pectoral muscle mass than males of the same group and males but not females, deprived of fruits accumulated more fat reserve than those deprived of insects. PCV and HBC did not differ between diets but increased over the eight weeks. 5. Weavers are likely obligate rather than facultative omnivores, with insects as being a more nutritive supplement than fruits. We conclude that nutrient limitation arising from environmental change or habitat alteration can impair body condition and affect physiological response to environmental seasonality in other obligate omnivores like the weavers.
1. Mexican territory is one of the centers of origin and dispersion of the genus Opuntia, where several of its species have been an important plant resource for people in arid and semi-arid zones. Opuntia streptacantha is widely distributed in Mexico, however, precise aspects of its geographic distribution and ecological status are still unknown. 2. Here, we modeled its potential distribution under paleoclimatic, current, and future conditions through maximum entropy and predictions from 825 records and seven environmental variables. 3. Potential distribution of Opuntia streptacantha in the interglacial period was contracted and slightly north than current distribution, with 42,850 km2 of optimal habitat including 27 km2 of very suitable habitat. 4. In other periods the central location of potential distribution coincides with the actual current distribution, but the period of the last glacial maximum was characterized by 282 km2 of very suitable habitat, absent in current and future periods. 5. Synthesis and applications. Our findings are relevant in the identification of regions where O. streptacantha may exist but has not yet been detected, in areas where it can potentially spread, suitable habitats due to climate change, and in the selection of areas for protection, conservation, and reproduction of species resistant to the hostile conditions of arid and semi-arid zones of Mexican territory, where the structure and composition of the vegetation will be affected in the next 100 years.
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.
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.
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.
Background and aims High-intensity grazing in Mongolian grasslands has led to the general deterioration of biodiversity and ecosystem functioning. Abundant evidence shows that grazing affects the structure and function of grassland ecosystems, especially under overgrazing. Methods We examined the effects of three grazing intensities (0, 1.92, and 3.08 sheep ha-1 a-1) on plant commu-nities, plant and soil C, N and P contents, and plant and soil C:N:P stoichiometry in a desert grassland in different years. Results Grazing did not affect plant coverage, richness, or N:P, and the plant community biomass, litter bio-mass and C:N and C:P were highest under a zero grazing intensity. Soil C:N changed with the year and grazing intensity. However, soil C:P and N:P were higher in 2018 than in 2016 and 2017. Conclusions Our study suggested that grazing promoted the flow of N between plants and the soil, especially at 3.08 sheep ha-1 a-1. Under grazing stress, plants maintained the potential for compensatory growth. Further-more, N was shown to be the limiting fertilizer component for plants growing in this area among the three grazing intensities.
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.
The encroachment of freshwater territories by invasive species is a global issue with its associated co-existence, displacement and facilitation of native species. The blackchin tilapia, Sarotherodon melanotheron is one of the most successful biological invasive species. Data on its apparent ecological consequences on native species are rare in Nigerian inland waters. Based on stomach contents analyses, diets, feeding strategies, and dietary niche breadths of two sympatric invasive S. melanotheron and native Nile tilapia Oreochromis niloticus populations in a tropical domestic water supply were assessed for possible convergence. Both species exhibited generalist feeding strategies subsisting mostly on algae but fish eggs and larvae were conspicuous preys of S. melanotheron. Dietary niche of S. melanotheron was wider than that of O. niloticus. Dietary niche overlap was high and significant between these sympatric species. These findings imply that competitive feeding interactions-including predations on vulnerable early life stages may potentially promote invasion success of S. melanotheron in Eleiyele Reservoir.
Studies have shown negative impacts of increased human pressures on biodiversity at local (alpha-diversity) and regional (gamma-diversity) scales. However, the diversity between local sites (beta-diversity) has received less attention. This is an important shortcoming since beta-diversity acts as a linkage between trends at the local and regional scales. Decreased beta-diversity means that local sites lose their distinctiveness, becoming more similar to each other. This process, known as biotic homogenization, is predicted to arise through the replacement of native specialists with native and non-native generalists. However, the mechanisms causing biotic homogenization have not been fully studied nor its impacts on different facets of biodiversity. We examined if land-use change due to human actions causes biotic homogenization of taxonomic, functional and phylogenetic diversity in bird communities of forested habitats in the state of Minnesota, USA. Our aim was to study if increased human pressure, which included human population density, land transformation, transport infrastructure, and electrical power infrastructure, was associated with increased similarity among bird point count sites. Our results showed that elevated human pressure was not related with increased biotic homogenization in this study region. Interestingly, increased human pressure appeared to increase the between-site functional diversity of bird communities. This association was driven by a decrease in local diversity, which, due to the nature of beta-diversity, led to an increase in between-site diversity. We highlight the importance of considering multiple facets of biodiversity and the use of beta-diversity in a conservation setting.
Phytoplankton plays a fundamental role in the ecology of ocean systems and is the key player in the global carbon cycle. At a time of global warming, understanding the mechanisms of its adaptation to temperature is therefore of paramount importance. Cosmopolitan planktonic species abundant in different marine environments provide both a unique opportunity and an efficient methodological tool to study the genomic bases of their adaptation. This is the case for the eukaryotic picoalga Bathycoccus prasinos, whose genomic variability we chose to study in temperate and polar oceanic waters. Using multiple metagenomic datasets, we found that ~5% of B. prasinos genomic positions are variable, with an overwhelming majority of biallelic motifs. Cold and temperate waters are clearly associated with changes in variant frequencies, whereas in transitional waters we found more balanced polymorphism at most of these positions. Mesophilic and psychrophilic gene variants are distinguished by only a few amino acid changes located at positions critical for physical and functional protein properties. These results provide new information on the genomic diversity of a cosmopolitan eukaryotic planktonic species and suggest “minimal mutational strategies” related to the properties of specific proteins at different temperatures.
1.- There is a strong decrease in liana diversity along latitudinal and altitudinal gradients at global scale, and there is a marked difference in liana diversity between tropical and temperate ecosystems. From these observations it has been proposed that cold temperatures would restrict the liana ecological patterns, because of the vulnerability of their vascular system to freezing-thaw embolism. However, there is scarce empirical evidence that support this idea in natural conditions. 2.- The goal of our study was to establish the functional mechanism behind the loss of liana diversity towards higher latitudes. For this purpose, we evaluated the change in liana performance and the trade-off between safety and efficiency of water transport along a latitudinal gradient in temperate rainforests of South America. We measured the ecological liana performance as the apical growth rate in ten liana species along a latitudinal gradient, and we related it with functional traits associated with the safety (vessel diameter, vessel density, wood density and root pressure) and efficiency of water transport (maximum hydraulic conductivity and percentage of lost conductivity). 4.- We found that lianas species inhabiting the southern (colder) site of the latitudinal gradient have low performance, with a 5-fold decrease in their apical growth rate compared to the northern sites. These would be consequence of a much lower water transport efficiency (26.1-fold decrease) respect to liana species that inhabit northern (warmer) sites, as an outcome of a higher freezing-thaw embolism (37.5% of PLC) and reduction of vessel diameter (3 times narrower). 5.- These results are clear evidence that cold temperature restricts liana performance and would act as a modeler of their latitudinal diversity pattern.
For more than three decades, the Asian turtle crisis has resulted in the decline of every native species in China. For some species, such as the yellow pond turtle (Mauremys mutica), wild populations have dwindled to near functional extinction. Previous studies show there is deep genetic divergence of M. mutica sensu lato between populations north and south of the Pearl River Drainage but no data to show if phylogeographic structure occurs within these two main types. In this study, we found clear phylogeographic structure. In northern types, we found two main clades, corresponding to mainland China and island clades (Taiwan and Yaeyema Islands) with uncorrected p values of 0.00-2.0% divergence in our 2353 bp concatenated mtDNA data set. For the southern types, we found three main clades corresponding to Hainan, Mainland (Vietnam/Guangxi) and the Annam pond turtle (Mauremys annamensis) with divergence ranging from 1.0-1.8% among these three groups. Moreover, the identification of northern and southern types by phenotype was roughly 98% accurate, which, coupling with the deep genetic divergence in mtDNA (5.5-6.7%) and in the 6056 bp nuDNA data set (0.16-0.37%) provide sufficient evidence for northern M. mutica to be an independent species, and individuals from the southern clade should be regarded as subspecies of M. annamensis. Finally, we provide the most comprehensive database to date which can be used to determine the region of origin for captive stock. Making the large captive populations of M. mutica, under the right conditions, potentially valuable for restocking or augmentation of wild populations.
Plants in suburban forests of eastern North America face the dual stressors of high white-tailed deer density and invasion by nonindigenous plants. The combination of chronic deer herbivory and strong competition from invasive plants could alter a plant’s stress- and defense-related secondary chemistry, especially for long-lived juvenile trees in the understory, but this has not been studied. We measured foliar total antioxidants, phenolics, and flavonoids in juveniles of two native trees, Fraxinus pennsylvanica (green ash) and Fagus grandifolia (American beech), growing in six forests in the suburban landscape of central New Jersey, USA. The trees grew in experimental plots that had been subject for 2.5 years to factorial treatments of deer access/exclosure X addition/no addition of the nonindigenous invasive grass Microstegium vimineum (Japanese stiltgrass). As other hypothesized drivers of plant secondary chemistry, we also measured non-stiltgrass herb layer cover, light levels, and water availability. Univariate mixed model analysis of the deer and stiltgrass effects and multivariate structural equation modeling (SEM) of all variables showed that both greater stiltgrass cover and greater deer pressure induced antioxidants, phenolics, and flavonoids, with some variation between species. Deer were generally the stronger factor, and stiltgrass effects were most apparent at high stiltgrass density. SEM also revealed that soil dryness directly increased the chemicals; deer had additional positive, but indirect, effects via influence on the soil; in beech PAR positively affected flavonoids; and herb layer cover had no effect. Juvenile trees’ chemical defense/stress responses to deer and invasive plants can be protective, but also could have a physiological cost, with negative consequences for recruitment to the canopy. Ecological implications for species and their communities will depend on costs and benefits of stress/defense chemistry in the specific environmental context, particularly with respect to invasive plant competitiveness, extent of invasion, local deer density, and deer browse preferences.
Comparing life history traits among populations that have been separated genetically for several hundred thousand years, but live in similar habitats on different continents, may help us understand how ecological and anthropomorphic factors shape life histories. We compared patterns of growth in body length and mass, and the influence of population density, habitat quality (NDVI), and reproduction on age-specific length and mass of male and female brown bears between Alberta, Canada, and Sweden. We found that Swedish females were significantly smaller in both length and mass than Alberta females. Swedish females also reached primiparity earlier and at a smaller mass and length. However, there were no continental differences in the patterns of growth in males. We found strong positive effects of NDVI, but only weak negative effects of population density on female mass and length in both areas. Generally, especially mass of Alberta females was more strongly affected by NDVI and density than for Swedish females. Reproduction had stronger negative effects on female mass in Alberta than in Sweden. We found no effects of NDVI and population density on male mass and body length in both areas. The larger variation in female growth and size between the areas, in contrast to males, may be related to differences in female reproductive investment due to differences in population trends, i.e., earlier reproduction in increasing populations or populations below carrying capacity, or to different selection pressures in the past, potentially due to human persecution. Swedish females exhibited characteristics typical of increasing populations, whereas Alberta females exhibited characteristics typical of stable or decreasing populations. The difference in reproduction investment means that Swedish bears can be harvested at higher rates, whereas Alberta bears must be managed more conservatively.
The Timber Rattlesnake (Crotalus horridus) has a large distribution spanning much of the eastern United States. Because temperature, habitat type, prey composition and abundance, and a variety of other factors may dictate reptile behavior, populations of conspecific species may exhibit behavioral differences across latitudinal and elevational gradients. Using radio telemetry, we tracked 10 adult Timber Rattlesnakes (7 males, 3 females) from May 2016 to June 2017 in southeastern Louisiana to examine the spatial ecology of male and non-gravid female snakes. Mean annual and seasonal home ranges of non-gravid female Timber Rattlesnakes were not statistically different from that of males. Mean seasonal home range sizes and average distances travelled of both sexes was smallest in winter, and had a general increasing trend beginning in spring with a peak in fall. These increases seemed to coincide with the breeding season, taking place from early July until the end of November. Comparison of this study with other studies throughout its distribution could have implications towards future management of conservation for other southern populations of Timber Rattlesnakes.
The Yunnan-Guizhou Plateau (YGP) is characterized by the distinctive isolated habitat of limestone Karst Islands and features the Wumeng Mountains (Mts), which divide the YGP into the two Plateaus of Yunnan and Guizhou. This study aims to assess the effects of past geographic and environmental isolation and climate fluctuation on the flora distribution in the YGP. To this effect, we analyzed the phylogeographical pattern and genetic structure for Myrica nana, a vulnerable species endemic to the YGP, based on chloroplast and nuclear ribosomal DNA sequence. The results suggest that the genetic and haplotype network structures are divided into at least two groups—cpDNA haplotype H2 (or nrDNA haplotypes h1, h2, and the native haplotype) mainly distributed to the east of the Wumeng Mts, and cpDNA haplotype H1 and haplotypes H3–H10 (or nrDNA haplotype h3) distributed to the west of the Wumeng Mts. A deep genetic split was noted within the two groups to reach 25 steps, especially for the cpDNA fragment variation. The east–west divergence reveals the existence of a natural geographical isolation boundary in the form of the Wumeng Mts, which divides the YGP into the Yunnan and Guizhou Plateaus. Therefore, there existed at least two glacial refugia during the Quaternary glacial period, along with a genetic diversity center, and at least two large geographic protection units for the vulnerable species of M. nana, distributed throughout the eastern and western sides of the Wumeng Mts. This study not only clarifies that the phylogeographical pattern and genetic structure for M. nana can be attributed to geographic and environmental isolation and climate fluctuation, but it also proposes an effective strategy to protect vulnerable species and the important wild flora of the YGP.
There is much concern about disruption of endocrine physiology regulated by steroid hormones in humans, other terrestrial vertebrates and fish by industrial chemicals, such as bisphenol A, and pesticides, such as DDT. These endocrine-disrupting chemicals influence steroid-mediated physiology in humans and other vertebrates by competing with steroids for receptor binding sites, disrupting diverse responses involved in reproduction, development and differentiation. Here I discuss that due to evolution of the progesterone receptor (PR) and mineralocorticoid receptor (MR) after ray-finned fish and terrestrial vertebrates diverged from a common ancestor, each receptor evolved to respond to different steroids in ray-finned fish and terrestrial vertebrates. In elephant shark, a cartilaginous fish, ancestral to ray-finned fish and terrestrial vertebrates, both progesterone and 17,20b-dihydroxy-progesterone activate the PR. During the evolution of ray-finned fish and terrestrial vertebrates, the PR in terrestrial vertebrates continued responding to progesterone and evolved to weakly respond to 17,20b-dihydroxy-progesterone. In contrast, the physiological progestin for the PR in zebrafish and other ray-finned fish is 17,20b-dihydroxy-progesterone, and ray-finned fish PR responds weakly to progesterone. The MR in fish and terrestrial vertebrates also diverged to have different responses to progesterone. Progesterone is a potent agonist for elephant shark MR, zebrafish MR and other fish MRs, in contrast to progesterone's opposite activity as an antagonist for aldosterone, the physiological 2 mineralocorticoid for human MR. These different physiological ligands for fish and terrestrial vertebrate PR and MR need to be considered in applying data for their disruption by chemicals in fish and terrestrial vertebrates to each other.
1. Latitudinal diversity gradient (LDG) is the increase in species richness towards the equator and is one of the most consistent patterns in biogeography, where current and historical processes contribute to shape the pattern. 2. Despite that LDG patterns have been described for some insects, the underlying mechanisms associated with community assembly and diversification along modern latitudinal diversity gradient pattern remain unknowledge for many groups. 3. Odonata is an old order of insects that originated during the Carboniferous and has diversified through different eras. Here, we defined co-occurrence based on the presence in ecoregions and 1°×1° grid cells of Odonata species in North America NA, to address their species richness, phylogenetic structure, and species diversification rate along the latitudinal gradient. 4. For the whole order, we found the highest species richness at mid-latitudes, while phylogenetic diversity showed a linear positive pattern along the gradient. Our results showed dragonfly assemblages were clustered along all the gradient, suggesting that environmental filtering sorted the assemblages. Whereas damselfly species assemblages were clustered at mid-latitude and overdispersed into both extremes of gradient, probably community assembly is driving by thermal gradients at mid-latitude, by competitive exclusion at south extreme, and by different origins of the biota at the boreal zone. Our results show that apparently most ancestral lineages of Odonata inhabit tropical zones, where diversified and dispersed to the temperate region, although likely also have been diversified into regions of NA, which might be linked with the highest species richness at mid-latitude for both suborders.