Showing papers in "Acta Oecologica-international Journal of Ecology in 2021"
TL;DR: In this article, a review of the history of the term "niche" is presented, focusing on its uses and the disagreements that have arisen over it within ecology, and a heuristic classification scheme for niche concepts is presented.
Abstract: Ecologists have long had a “love-hate” relationship with the niche concept. Sometimes referred to as a term best left undefined, the niche concept nonetheless spans ecology. Deeply rooted in the Darwinian struggle for survival, “niche” has been a core, although slippery, idea in ecology since its origins. What ecologists mean by niche has changed semantically over time. In this paper, we review the history of the term, focusing on its uses and the disagreements that have arisen over it within ecology. Because classic niche concepts are not exclusive and share some similarities, we disentangle them into key theoretical components to create a heuristic classification scheme for niche concepts. We, therefore, analyze coherence on rhetoric within the ecological literature, by classifying how ecologists use niche concepts in their writing, aiming at clarifying communication on what is being studied. To assess if modern ecological theories are coherent in their usage of the niche concept, we surveyed a sample of three research areas: ecological niche modeling, coexistence between species and meta-communities. We found that research agendas are segregated when it comes to rhetoric about niches. Ecologists have long tried to achieve a truly unifying biodiversity theory, or at least a universal definition of niche. We, however, move in the opposite direction and suggest that the niche concept should be dismembered into its key components, highlighting which elements of the concept are being addressed and analyzed. Explicitly stating to which niche concept a study is referring may enhance communication among researchers from different backgrounds and perhaps alleviate this century-old dilemma.
16 citations
TL;DR: In this article, the authors used the Asian mud-dauber wasp Sceliphron curvatum (Hymenoptera: Sphecidae), which arrived in Europe 40 years ago, to show that cities may be used by alien species to enlarge their distribution into non-optimal areas.
Abstract: Insects are highly involved in accidental introductions in non-native areas. Potential distribution modelling is routinely used to predict the dynamics of such range expansions, giving insights on which areas are climatically suitable for establishment. However, even in areas where climatic conditions are unsuitable, colonization may be still possible in sub-areas with particular, human activity-driven microclimates, such as cities. We used as a model species the Asian mud-dauber wasp Sceliphron curvatum (Hymenoptera: Sphecidae), which arrived in Europe 40 years ago, to show that cities may be used by alien species to enlarge their distribution into climatically non-optimal areas. By using an average consensus from six different models, we predicted that, based on climate, S. curvatum would find the highest suitability in most part of Mediterranean basin, which are characterized by high summer temperatures and reduced climatic oscillations. The species is indeed often observed in such areas, but also in Central Europe, where suitability is overall lower. At such latitudes, however, the wasp was more often found in cities (which have the highest suitability) than in peri-urban and rural areas, possibly according to the urban ‘heat island’ effect. In Southern Europe, where climate is overall more favourable for the species, suitability tended to be more similar in both urban and rural environments, and urban detections were indeed rarer. The inclusion of population density in the model improved the suitability of Northern areas in an expected urbanization-driven jeopardized pattern. Hence, S. curvatum would be able to colonize in the future at least some climatically unsuitable Northern areas, reaching up to 70° latitude, by using cities as the main sites for establishment.
14 citations
TL;DR: It is demonstrated that sugarcane expansion over pasturelands reduces the total abundance of the soil epigeic fauna, and that effects on fauna diversity vary from broad to fine taxonomic resolutions.
Abstract: The epigeic fauna, ground surface-dwelling invertebrates that inhabit leaf-litter, acts on multiple soil processes and key ecosystem services and is threatened by global land-use change (LUC). In Brazil, LUC for sugarcane expansion over extensive pasture has been taking place for promoting bioenergy production; however, conventional sugarcane cultivation includes monoculture, periodic soil tillage and agrochemicals may alter the quantity and quality of crop residue inputs, soil habitats and communities of soil fauna. Thus, a field study at three sites in central southern Brazil was conducted to evaluate if the expansion of sugarcane cultivation affects soil epigeic fauna. In each site, we sampled epigeic fauna in areas under LUC from native vegetation to extensive pasture, and from that to sugarcane. The epigeic fauna was collected using pitfall traps and then quantified and classified in taxonomic groups (Order, Class, Family). In addition, as a focal organism group, ants were classified at the species level. Overall, 13 taxonomic groups were identified, in which the Formicidae family was the most abundant group (i.e., 67% of individuals), followed by Diptera (13%), Araneae (5%) and Coleoptera (4%). Land transition from native vegetation to pasture increased fauna abundance by 27% but reduced the diversity of epigeic fauna community by 43%. In contrast, sugarcane expansion over extensive pasture reduced fauna abundance (−22%), did not alter the diversity of the invertebrate community at a broad taxonomic level, but decreased species richness of the dominant taxa (ants) by 55%. Ant individuals were classified into 37 species, allowing to verify that sugarcane cultivation over pastures decreased both the abundance and richness of ants and altered community composition. Ant species Ectatomma brunneum were more sensitive to LUC and, therefore, could be characterized as potential indicators of disturbed environments. We demonstrate that sugarcane expansion over pasturelands reduces the total abundance of the soil epigeic fauna, and that effects on fauna diversity vary from broad to fine taxonomic resolutions. Further studies are needed to evaluate if the declines in fauna abundance and ant species richness impair specific soil functions and soil-related ecosystem services.
10 citations
TL;DR: It is concluded that seed germination success in fleshy fruits including those of alien species, varies with seed treatment by different vertebrate dispersal agents, and their net effect on seeds, may have consequences on species invasion success.
Abstract: The fleshy fruits of exotic Opuntia ficus-indica (L.) Mill and Opuntia robusta (Haw.) Haw (Cactaceae family) are consumed and dispersed by many vertebrates, which likely influences their invasion success. We tested whether seed ingestion by Pied Crows (Corvus albus) and other smaller birds (African Pied Starling Lamprotornis bicolor and the Red-eyed Bulbul Pycnonotus nigricans) improve the germination and speed in O. ficus-indica and O. robusta. Controlled germination trials for two Opuntia species were set up using the seeds extracted from faecal material, depulped seeds, and intact fruits. Overall, results show that seed germination for O. robusta was significantly higher than for O. ficus-indica. There were significant differences in seed germination between treatments of two Opuntia species, with the total mean germination of seeds defecated by the Pied Crows being equivalent to that of seeds defecated by the other smaller birds but significantly greater than the other treatments (i.e., depulped seeds and intact fruit). We noted that removal of the fruit pulp from seeds significantly improved germination in both Opuntia species compared to intact fruits. The O. robusta seeds defecated by the smaller birds had significantly greatest and most accelerated germination of all other treatments followed by the seeds defecated by the Pied Crows. Seeds of O. ficus-indica defecated by the Pied Crows had significantly greater germination than the seeds ingested by smaller birds. We conclude that seed germination success in fleshy fruits including those of alien species, varies with seed treatment by different vertebrate dispersal agents, and their net effect on seeds, may have consequences on species invasion success.
8 citations
TL;DR: It is suggested that one month of cattle removal to grazing rotational management in introduced Brazilian pastures can be a useful strategy to, besides conserving the grass, also conserving dung beetle diversity, and consequently the ecological functions performed by them.
Abstract: Pasture management techniques may affect the biodiversity of insects beneficial to pastures, such as dung beetles. Cattle grazing removal over a short-term is widely used in introduced Brazilian pastures. However, the impact of this management on dung beetles is still unknown. This study evaluated the taxonomic (species richness, abundance, biomass, species composition, Shannon, and Simpson indexes) and functional (functional richness FRic, functional dispersion FDis, functional evenness FEve, and community-weighted means of trait values CWMs) dung beetle assemblages response to cattle grazing removal over a short-in introduced pastures. We sampled dung beetles, with pitfall traps baited with cattle dung and carrion, simultaneously in pastures with constant cattle grazing (control), and one, three, and five months after cattle grazing removal in Aquidauana, Mato Grosso do Sul, Brazil. Taxonomic metrics and FRic, FDis, and FEve did not differ among control and pasture treatments. We found that pastures with one month of cattle removal maintain the same CWM coprophagous diet from the control, and higher CWM biomass in relation to control. Although cattle grazing removal, at least over the short-term, does not cause a negative impact on dung beetle taxonomic metrics and functional diversity indexes, two important traits associated to dung removal are negatively affected after three months of cattle removal. Thus, we suggest that one month of cattle removal to grazing rotational management in introduced Brazilian pastures can be a useful strategy to, besides conserving the grass, also conserving dung beetle diversity, and consequently the ecological functions performed by them.
8 citations
TL;DR: Li et al. as mentioned in this paper investigated the richness and cover of terrestrial and epiphytic fern species in the landscape of Xishuangbanna, Yunnan, China.
Abstract: The richness and cover of tropical fern life-forms — terrestrial and epiphytic — vary due to their ecology and evolutionary history. It is important to understand the responses of both terrestrial and epiphytic species in relation to topography, as elevation and other aspects, to better predict their distribution. This study has investigated the richness and cover of terrestrial and epiphytic fern species in the landscape of Xishuangbanna, Yunnan, China. The ferns were classified as either rare or common based on their occurrence and the cover values from 75 transects. A General Linear Model was created to understand the impact of the elevation and topographic aspects on the rare and common fern species. A total of 130 ferns species were found. Out of the total richness, 74% of species were considered rare and assessed as having either a narrow or a wide distribution but low frequency. The rarity increased up to 90% for the epiphytic species. Both rare and common epiphytic species had higher richness and cover values at higher elevations. While common epiphytes had higher cover values at a high elevation in the northern aspect, the rare epiphyte species were richer at a higher elevation for both aspects. The richness and cover of the terrestrial species was negatively correlated with elevation and there was a significant interaction. Specifically, most of the rare and common terrestrial ferns were in the lowland sites of Xishuangbanna (from 600 m a.s.l.) However, only 20 species out of the total 130 species contributed to a total cover above 50% with the other species having only a minor density. Our results emphasize the high number of rare species with a low occurrence and show there to be a conservation concern in the fragmented tropical landscape of southern Yunnan.
8 citations
TL;DR: In this article, the authors show that exposure to wasp buzzing reduces development time and final pupal weight of monarch caterpillars, leading to shorter developmental time and suboptimal weight.
Abstract: Predation risk is a key factor that impacts the growth and behavior of organisms. The ability to detect and react to potential predators provides a major competitive advantage, but the energetic costs associated with anti-predator behaviors can be severe. Monarch (Danaus plexippus) (Lepidoptera: Nymphalidae) caterpillars detect airborne predators through auditory predator cues, identifying the sound of a potential threat and exhibiting anti-predator behavior accordingly. Previous work on this species has examined only short-term behavioral changes in response to predation risk. We exposed monarch caterpillars to recorded predator cues in order to provoke anti-predator behaviors over an extended period of time in an effort to determine the long-term fitness costs associated with these behaviors. Our results show that exposure to wasp buzzing reduces development time and final pupal weight. These results imply that the stress of predation risk causes monarch caterpillars to accelerate their development, pupating more quickly in order to avoid the threat of predation. This shorter developmental time leads to the caterpillars pupating at a suboptimal weight, potentially reducing their future fecundity and lowering their ecological fitness as a whole.
8 citations
TL;DR: In this paper, the authors analyzed the foliar N content of seven plant taxa representing different functional groups of the understory vegetation and correlated them to modeled deposition datasets to assess the impact of atmospheric nitrogen deposition on ecosystems and found positive correlations of foliar n concentrations with increasing deposition in conifer saplings (Picea abies and Abies alba), the dwarf shrub Vaccinium myrtillus and graminoid Luzula luzuloides.
Abstract: Excessive atmospheric nitrogen deposition is known to alter nutrient cycles and species composition in temperate forest ecosystems. Foliar N concentrations reflect the nutrient status of plants and can be used to assess the impact of atmospheric N deposition on ecosystems. Our objective was to test whether the foliar N content reflects increasing N deposition in the understory vegetation of temperate forests on acidic soil. Therefore, we analyzed the foliar N content of seven plant taxa representing different functional groups of the understory vegetation and correlated them to modeled deposition datasets. Linear mixed models revealed no relationship of N deposition with foliar N concentrations across all species examined but decreasing foliar concentrations with increasing soil C/N ratio. Nevertheless, we found positive correlations of foliar N concentrations with increasing deposition in conifer saplings (Picea abies and Abies alba), the dwarf shrub Vaccinium myrtillus and the graminoid Luzula luzuloides. Such an increase was, however, not found in saplings of broad-leaved trees (Fagus sylvatica and Quercus petraea/robur) and the moss Polytrichum formosum. This suggests marked species-specific differences in nitrogen uptake and allocation. Foliar N concentrations were more strongly correlated to NOy than NHx and to wet than dry deposition. Since foliar N concentrations were correlated to deposition while the species’ cover was not, they may provide a valuable indicator of N deposition.
8 citations
TL;DR: At the scale of this study, environmental conditions represented a more important driver of avian haemosporidian metacommunity structure than host-related traits, suggesting an important role of environmental filtering structuring parasite assemblages at the landscape level.
Abstract: Metacommunity ecology studies how species compositional patterns and their distributions vary across local and regional scales and provides insights on processes driving the distribution of communities. Avian haemosporidians comprise a diverse and widely distributed parasite taxon; some studies have analyzed their alpha and beta diversity patterns. Yet, metacommunity structures of avian haemosporidians and thus relevant biotic and abiotic variables explaining such structures at the landscape scale (i.e., 10–200 km) have not been assessed. We studied the metacommunity structure of avian haemosporidian mtDNA cyt b lineages and the infected avian host assemblage across four different elevations in Central Veracruz, Mexico. We performed variation-partitioning analyses to evaluate the contribution of host-related traits and climatic variables to the metacommunity. We found a richness of 78 lineages within 38 infected species of birds. At the component community level, we observed that bird species infected with a lower number of parasite lineages (e.g., 8) (i.e., nested structure). However, this nested pattern was due to the restricted spatiotemporal co-occurrence of hosts and parasites, given the high degree of turnover across elevations. Host-related traits (functional, transmission-associated, and phylogenetic relationships) only explained a small fraction of the variation (4.4%) in parasite lineage composition across avian hosts. At the habitat level, there was a group turnover by parasite genera across elevation (i.e., quasi-Clementsian structure), which was partly explained by climatic variables (mean annual temperature and annual diurnal range; 27.6%) that may constrain parasite reproduction and vector distribution across the environmental gradient. At the scale of our study, environmental conditions represented a more important driver of avian haemosporidian metacommunity structure than host-related traits, suggesting an important role of environmental filtering structuring parasite assemblages at the landscape level.
8 citations
TL;DR: The results suggest that the double-duplex passive integrated transponder tagging technique is useful in quantifying mutualistic or predatory interactions between multiple tree and rodent species.
Abstract: Seed hoarding by rodents plays a significant role in shaping mutualistic or predatory interactions between tree and rodent species in forest ecosystems. However, it is still challenging to identify the seed-rodent interaction at individual level so as to reveal the differences in mutualistic or predatory interactions between seeds and rodents due to lack of efficient methods of tracking seed hoarding behaviour and seed fate. Here, by using the double-duplex passive integrated transponder tagging technique, we investigated seed hoarding behaviour of two rodent species (Niviventer confucianus with larger body size; Apodemus draco with smaller body size) on seeds of two tree species (Quercus variabilis with larger seeds, thicker seed coat, higher tannin and starch contents; Camellia oleifera with smaller seeds, thinner seed coat, and lower tannin but higher fat contents) in a subtropical forest of China. We found N. confucianus preferably consumed and scatterhoarded seeds of Q. variabilis. In contrast, A. draco preferably consumed and scatterhoarded seeds of C. oleifera. Our study showed significant difference in mutualistic or predatory interactions between trees and rodent species, which is likely to be associated with the functional traits of seeds and rodents. Our results suggest that the double-duplex passive integrated transponder tagging technique is useful in quantifying mutualistic or predatory interactions between multiple tree and rodent species.
7 citations
TL;DR: In this paper, the authors explore the causes of the Orloci paradox and discuss how the normalization methods that are included in virtually all compositional dissimilarity measures affect the way in which species abundances are modeled.
Abstract: A well-known problem of the Euclidean distance is that it is not always appropriate to explore the multivariate structure of community composition. This is because all distances of the ‘Euclidean family’ may lead to the paradoxical condition for which two samples with no species in common may be more similar than two samples with the same species list. This effect is generally known as the Orloci paradox. To avoid this problem, some kind of data normalization has to be performed. Therefore, the main question of this short paper is: what is gained and what is lost by moving from the Euclidean distance to compositional dissimilarity? To answer this question, I first explore the causes of the Orloci paradox. Next, I discuss how the normalization methods that are included in virtually all compositional dissimilarity measures affect the way in which species abundances are modeled.
TL;DR: A longer-term fire suppression or a return fire interval of less than 4 years may be necessary to reduce the resilience of the savanna tree component, considering the ecosystem functions analyzed in this study.
Abstract: Changes in savanna's fire regimes, either through fire suppression or through an increase in fire frequency, can negatively affect their resilience We evaluated the extent to which the aboveground biomass, diversity (taxonomic and functional) and resilience (functional redundancy and functional response indices) of savanna tree communities differ between burned and unburned plots Burned plots experienced two fire events over the ten-years prior to sampling, while unburned plots experienced fire suppression over the same time period We found that aboveground biomass was 40% smaller in burned plots, indicating that fire regimes must be included as a source of variation in models estimating the potential of savannas to store carbon Burned plots had a higher functional diversity of vegetative traits but a smaller functional diversity of reproductive traits, indicating that generalizations about the effect of fire on tree functional diversity should be viewed with caution Periodic fires can benefit savanna tree biodiversity by maintaining the balance between light-demanding and shade-tolerant species but can also increase the dominance of species with less specialized reproductive traits that do not rely on animal interactions Burned plots had slightly lower functional redundancy but similar functional response diversity compared to unburned plots, suggesting that both communities harbor tree species that might respond positively or negatively to fire and, therefore, will be able to maintain the ecosystem functions considered under a future scenario of fire-suppression or increased fire frequency Therefore, a longer-term fire suppression (>10 years) or a return fire interval of less than 4 years may be necessary to reduce the resilience of the savanna tree component, considering the ecosystem functions analyzed in this study
TL;DR: In this article, the authors investigated the effect of plant invasion, litter quality and altitude on decomposition rate at multiple sites along an elevational gradient in the Kashmir Himalaya, and found that invasive L. vulgare by altering the litter decomposition rates could greatly influence the cycling of nutrients in the invaded landscapes.
Abstract: Litter decomposition, a key biogeochemical cycling process regulating carbon and other nutrient balances, is driven by several factors including vegetation composition, litter quality and local environmental conditions. However, the relative role of these drivers on decomposition process in the context of plant invasions has been little investigated, particularly in the Himalaya. In this study, we investigated the effect of plant invasion, litter quality and altitude on decomposition rate at multiple sites along an elevational gradient in Kashmir Himalaya. We used the standard litterbag incubation experiment to compare decomposition rates among the plots with- and without global plant invader Leucanthemum vulgare, using both standard (cellulosic filter papers) and local (pine needles) litter types. Our results show that invasion had a significant effect on decomposition rates of both the litter types with relatively higher decomposability in case of invaded plots than the uninvaded ones. Litter quality was the predominant factor in controlling the decomposition rate as evidenced from much higher decomposability (about eight times) of filter papers as compared to pine needles. Also, altitude had a significantly negative effect on decomposition rate of both the litter types, possibly through the influence on abiotic conditions (temperature and precipitation in particular). Our results highlight that, although multiple factors are affecting the litter decomposition at the regional scale, the litter quality exerted the stronger influence. Our study suggests that invasive L. vulgare by altering the litter decomposition rates could greatly influence the cycling of nutrients in the invaded landscapes.
TL;DR: In this article, the authors tested whether the diversity of birds along elevational gradients in the Serra do Caparao, a mountain of the Brazilian Atlantic Forest, is explicable by the mid-domain effect.
Abstract: Among the theories that attempt to explain the elevational distribution of metazoan species along elevational gradients, the Mid-Domain Effect (MDE) is one of most debated and criticized. Here, we test whether the diversity of birds along elevational gradients in the Serra do Caparao, a mountain of the Brazilian Atlantic Forest, is explicable by the MDE. We sampled an elevational gradient between 970 m.a.s.l. and 1970 m.a.s.l. of forest vegetation, with elevational bands every 100 m. We observed a hump-shaped richness pattern of birds along the gradient, with more species in intermediate elevations. It decreased at lower and higher elevations, thereby following a unimodal distribution. Distribution of species richness indicated a high correlation with the tested MDE null model. The result was the same for endemic species. Considering the total bird species registered, up to 30% are endemic and 9 are endangered. Threatened species richness followed a different elevational distribution along the gradient: three species occurred at the lower elevations, two at the interquartile elevations and four at the highest elevations. Despite finding more species in the intermediate elevations, the areas of low and high elevations are also important for the maintenance of endemic and threatened species. To test the MDE theory and compare our results with other studies, we highlight the importance of standardized samplings and habitats. Moreover, we focus on the characterization of the surrounding landscape, which can also influence the richness of bird species diversity.
TL;DR: In this article, the authors studied leaf litter decomposition of Betula utilis, which is the main timberline species of Western Himalaya, and placed 144 litterbags (each containing 10g of oven dried litter) at three geographically separated sites.
Abstract: Litter decomposition plays a vital role in carbon and nutrient budget of forest ecosystems, but our understanding of this process for high altitude ecosystems, especially the timberline zone, is not very clear. We studied leaf litter decomposition of Betula utilis, which is the main timberline species of Western Himalaya. We placed 144 litterbags (each containing 10 g of oven dried litter) at three ‘spatially well separated sites’ in Oct 2014, to study the direction and magnitude of change in key variables associated with leaf litter decomposition and to test for generality of decomposition process across these spatially distant sites. The results revealed that initial nutrient concentration and lignin content of litter was significantly different for the sites. Further, magnitude of mass loss and decay rate was found to be greater for up to 34 weeks (19.03 ± 4.55% and 0.35 ± 0.06 yr−1 respectively), which reached 47.01 ± 1.98% and 0.17 ± 0.01 yr−1 respectively, after 4 years. N, P and K concentrations showed sharp decease for up to 34 weeks, after which N consistently increased with incubation time, whereas P and K concentrations were relatively stable. The lignin and cellulose contents decreased consistently with incubation time (from 12.29 ± 1.21% to 5.21 ± 0.50% and from 16.87 ± 1.01% to 8.25 ± 0.50% respectively). There were significant increases in C:N and lignin:N ratios for up to 34 weeks, followed by a continuous decrease thereafter. The change in various variables associated with litter decomposition was not consistent among the sites and the magnitude of change was greater during initial stages due to leaching of labile components. The increase in N and decreases in C:N and lignin:N ratios with incubation time might be due to microbial immobilization of N and are important for nutrient conservation in timberline ecosystems, as such changes are related to faster decomposition of recalcitrant fraction of litter, N mineralization and building of soil nutrient pool.
TL;DR: In this paper, the congeneric lagomorphs Lepus timidus and L. europaeus share allopatric distributions in many areas of Europe characterised by competitive exclusion and hybridisation.
Abstract: The congeneric lagomorphs Lepus timidus and L. europaeus share allopatric distributions in many areas of Europe characterised by competitive exclusion and hybridisation. We investigated prospects for these species under climate change in northern England uplands. We created ensemble models predicting niche realisation for these species, influenced by abiotic and biotic factors, estimating niche overlap in geo-environmental space. The two species occupy distinctly different niches, influenced more by vegetation preferences than climatic differences. The current climate niche for L. timidus featured higher elevations with cooler temperatures and 168 km2 range extent. Its current habitat niche scale was larger at 269 km2, comprised entirely of upland dwarf shrubs: heather, cotton grass, moorland grasses. By contrast, the current climate niche predicted L. europaeus occupying lowland areas with a milder climate and range extent of 252 km2. Its current habitat niche was also greater, 401 km2, being mostly improved grassland. Competition was presently limited. The current niche predictions showed very little geographic overlap between the species. Niche overlap measured by Schoener Index was low: current climate niche 0.16; current habitat niche 0.07. The future climate niches for 2050 (IPCC RCP2.6), predicted L. timidus range contracting to 19 km2, on hilltops and L. europaeus range expanding to 765 km2. Consequently L. timidus range would be wholly within the L. europaeus range. In many contact zones throughout Europe, L. europaeus outcompetes L. timidus; however, in the Peak District their distributions are largely distinct. Future replacement of L. timidus by L. europaeus may be engendered by dietary convergence, should a warmer climate cause a transition of upland dwarf shrub vegetation to grasses.
TL;DR: In this article, an updated overview of pollinator conservation globally is provided, focusing on how France and Belgium have reacted to the observed decline of pollinators, and examine their national interpretations, conservation actions and research contributions.
Abstract: The decline of pollinators has been demonstrated scientifically and this phenomenon is widely recognized by both the general public and by stakeholders. Since pollinators face different threats that are all linked to human activities, there is a unique and unprecedented responsibility for people to conserve pollinators, requiring political action to counter the substantial worldwide risk of pollinator loss. As our perception of the situation is rapidly changing, as a result of the steady accumulation of international and national reports as well as new scientific findings, we propose here to provide an updated overview of pollinator conservation globally. We present the key messages and the proposed solutions found in international reports and assessments, how European countries have interpreted these solutions proposed in the context of existing international frameworks. Next, we analyze how scientific research is addressing the issue of pollinator conservation through different international, European and national programs. The analysis of the keywords used in published scientific articles also allows us to characterize how the scientific community has engaged with this issue over time. Finally, we focus on how France and Belgium have reacted to the observed decline of pollinators, and examine their national interpretations, conservation actions and research contributions.
TL;DR: The research on soil seed banks, seed germination and dormancy, and seed dispersal of poisonous plants in the world's grasslands, based on a review of 172 references, is summarized to help researchers and managers in the study of seed ecology and the control strategy of poisoned plants.
Abstract: In degraded grasslands, luxuriant growth and rapid expansion of poisonous plants threaten livestock safety and reduce forage quality. Most of the poisonous plants propagate through seeds, but previous studies have paid insufficient attention to seed ecology, leading to a lack of sufficient support for ecological research regarding the formulation and implementation of relevant prevention and control methods. Based on a review of 172 references (1933–2020), we have summarized the research on soil seed banks, seed germination and dormancy, and seed dispersal of poisonous plants in the world's grasslands. The plants involved are Euphorbia esula, Eupatorium adenophorum, Lantana camara, Stellera chamaejasme, Achnatherum inebrians, genera of Senecio, Delphinium, Cicuta, Aconitum, Lupinus, Halogeton, and locoweed, which refers specifically to a kind of poisonous plants of Astragalus and Oxytropis genus containing swainsonine. There are some commonalities in the seed ecology of different poisonous plants in grasslands, including the persistence and surface aggregation of soil seed banks, as well as primary, long-distance dispersal by wind and animals. However, there are many differences between poisonous plants in terms of soil seed density, preference conditions of seed germination, seed dispersal media, and distance. For controlling the spread of poisonous plant seeds must reduce the disturbance to the surface soil and prohibit grazing during the active stage of seed rain. We recommend future studies investigate the influence of grazing on seed germination and propagation, the formation and fall of seed rain, and the impact of global change on poisonous plants. This review will be helpful for grassland researchers and managers in the study of seed ecology and the control strategy of poisonous plants.
TL;DR: In this paper, the authors investigated plant communities and species regeneration at a cut-slope area in Malaysia whilst examining the relationship between species diversity and soil erosion and found that high plant diversity was effective in enhancing soil properties thus, improving soil shear strength as plant coverage increased.
Abstract: Slope cuts caused by road construction, influence vegetation and soil properties which lead to ecological degradation and soil erosion. Cut-slope soils are infertile, creating unfavourable conditions for plant growth and a reduction of plant species. We investigated plant communities and species regeneration at a cut-slope area in Malaysia whilst examining the relationship between species diversity and soil erosion. Experimental plots were set at three different vegetation coverage intensities; 0% (A), 10% (B), and 50% (C). Treatment C recorded the highest plant coverage, plant density, species richness, plant diversity, and evenness index over time. In contrast, as there was no vegetation at the start of the experiment, succession rate was the highest in treatment A (bare plot) followed by B and C. The succession rate was lower in C due to high competition between the existing plant communities for space, nutrients, sunlight and water. The plot with the highest vegetation coverage (C) showed improved slope stability for it recorded a significant reduction in soil saturation level and erosion rate whilst increasing the shear strength. Dicranopteris linearis, a fern species was the most dominant species in all treatments for it is a pioneer species that thrives in harsh environment. High plant diversity was effective in enhancing soil properties thus, improving soil shear strength as plant coverage increased. Hence, treatment A consistently displayed the highest soil shear strength followed by treatments B and C.
TL;DR: In this paper, the influence of shifts in high nucleic acid content (HNA) and low NCA (LNA) bacteria on the degradation of TEP with emphasis on BGase activity was evaluated.
Abstract: Heterotrophic bacteria that differ in their nucleic acid content are frequently observed in aquatic environments. However, their relevance and roles in organic matter utilization in monsoon-influenced tropical estuaries have not been addressed. Transparent exopolymer particles (TEP) are one of the carbohydrate rich organic matter forms in aquatic environments, and their breakdown is mostly mediated by a heterotrophic bacterial ectoenzyme, i.e., β – glucosidase (BGase). The present study evaluated the influence of shifts in high nucleic acid content– (HNA) and low nucleic acid content – (LNA) bacteria on the degradation of TEP with emphasis on BGase activity. For this, monthly observations were carried out along the Zuari estuary, India, on the abundance of HNA, LNA bacteria, bacterial production (BP), and BGase activity. The results showed that the contribution of HNA bacteria to total bacterial count was high and positively influenced the BP and BGase activity during the non-monsoon seasons, which represents a well-mixed water column. During this time, HNA also influenced the active utilization of TEP. Whereas, LNA bacteria dominated during the monsoon, wherein the water column is strongly stratified, and showed decoupling with BGase activity, irrespective of the depth. Redundancy and response curve analyses revealed that the interactive effect of monsoon (rainfall) and stratification significantly altered the bacterial activity in this estuary. Besides, the variability in side scatter (SSC), and fluorescence intensity (FL 1) of HNA and LNA bacteria suggest that these two groups play distinct ecological roles in the tropical estuarine systems. Unravelling the links between the different nucleic acid content bacteria and their phylogenetic composition can provide insights into their functional roles in monsoonal estuaries.
TL;DR: In this paper, the effect of different functional types of BSC from the Monte desert on soil moisture and nutrients, N fixation, respiration, grass emergence, growth, and C/N was evaluated.
Abstract: Biological soil crusts (BSC) are widespread in the Monte desert. BSC, by fixing atmospheric N and retaining soil moisture, may enhance grass emergence, growth, and nutritional value. Our aim was to evaluate the effect of different functional types of BSC from the Monte desert on soil moisture and nutrients, N fixation, respiration, grass emergence, growth, and C/N. We sowed Leptochloa crinita seeds in pots with different BSC types (dominated by cyanobacteria, squamulose phycolichens, squamulose cyanolichens, gelatinous cyanolichens, and mosses) under two irrigation treatments: well watered and drought. We determined soil, BSC and grass properties related to nitrogen, phosphorus, and water cycles. In soils under BSC, we determined moisture, nitrate, and phosphate at two depths. In BSC, we determined total N, organic matter, ammonium, respiration, and δ15N. Finally, in grasses growing under BSC, we determined seedling emergence, grass biomass, C/N, and δ15N. All BSC types except cyanobacteria increased soil total N, ammonium, and respiration rates compared to bare soils under drought conditions. Cyanobacteria BSC increased soil moisture under drought conditions, while squamulose phycolichens and mosses increased it under well watered conditions. All BSC types increased underlying soil nitrate under well watered conditions, and decreased phosphate in at least one experimental condition. All BSC types improved at least one grass variable: cyanobacteria decreased C/N; squamulose cyanolichens increased emergence and decreased C/N; squamulose phycolichens increased emergence and biomass; gelatinous cyanolichens decreased C/N; and mosses increased emergence, biomass, and decreased C/N. The differential effects of each BSC type on soil and grass variables, under drought and well watered conditions, suggest the importance of BSC functional diversity on ecosystem functions of water regulation and nutrient cycling.
TL;DR: This paper reviewed feeding habits and temporal behaviour of the American mink introduced to Europe and concluded that American minks showed a polyphasic or cathemeral locomotor pattern, being active both during the day and the night in Europe and tending to limit encounter probabilities with native, larger mustelids.
Abstract: The American mink Neovison vison is an invasive species in Europe with a number of expanding populations in over 20 countries. In this work, we reviewed feeding habits and temporal behaviour of the American mink introduced to Europe. We summarised the results of 30 studies on diet of this mustelid and of 5 studies on activity rhythms. Trophic niche breadth was high in Europe and increased with increasing sampling period, thus emphasizing that American mink may shape its diet according to the seasonal availability of potential prey. American minks showed a polyphasic or cathemeral locomotor pattern, being active both during the day and the night in Europe and tending to limit encounter probabilities with native, larger mustelids. Acceptance of programs of eradication/numerical control are linked to the awareness of impact by this semiaquatic mammal and to recent sightings of free-ranging individuals. Numerical control of this charismatic, invasive mammal species may thus encounter a strong opposition by the general public, particularly because its presence and its impacts are poorly known. Educational campaigns and consultation with all potential stakeholders should be addressed to design effective decision-making processes.
TL;DR: It was found that the red-handed tamarin was more likely to emit more territorial calls when listening to pied tamarins than to its own species in sympatric areas, but found no differences in vocal responses from either species in relation to agonistic calls or duration of display in sympathetic areas.
Abstract: Aggressive behaviors are widespread among territorial species and asymmetrical aggressiveness may imply differential access to resources. At a larger scale, such asymmetry may also drive shifts in geographic distributions. The pied tamarin (Saguinus bicolor) is an endangered Amazonian primate species with a small natural range. In recent decades further reduction of its range has been observed coincident with the expansion of the range of the red-handed tamarin's (Saguinus midas), which appears to be encroaching into the area otherwise occupied by the pied tamarin. Here we test if, at range boundaries, red-handed tamarin produces more aggressive vocalizations than the pied tamarin. We performed a series of 96 playback trials presenting both congeneric and conspecific long calls to sixteen groups of red-handed tamarins and fourteen of pied tamarins. We recorded their territorial, agonistic, alarm vocalizations, and the duration of their calling displays after broadcasts. In doing so, we assessed whether agonistic displays were more likely to occur in response to congeneric than conspecific calls in areas of sympatry. We found that the red-handed tamarin was more likely to emit more territorial calls when listening to pied tamarins than to its own species in sympatric areas, but found no differences in vocal responses from either species in relation to agonistic calls or duration of display in sympatric and allopatric areas. Furthermore, the red-handed tamarin emitted more alarm calls when listening to pied tamarin, independently of the geographic circumstances. Overall, we found that acoustic displays may be mediating species interaction in areas of sympatry. Together, these observations are suggestive of behavioral interference, including the competitive displacement of pied tamarin by red-handed tamarins.
TL;DR: In this paper, the authors evaluated a river turtle assemblage over a 50-year study period (1969-2019), during which the assemblages was impacted by harvesting, habitat degradation, a record-shattering flood, and the removal of a small dam.
Abstract: Long-term studies are essential for understanding how and to what extent various stressors impact long-lived species, such as turtles. Turtle populations are declining globally. Empirical data from long-term studies of turtles are largely lacking, which hinders the development of effective conservation programs. We evaluated a river turtle assemblage over a 50 year study period (1969–2019), during which the assemblage was impacted by harvesting, habitat degradation, a record-shattering flood, and the removal of a small dam. Our objective was to determine how the turtle assemblage, Graptemys geographica population (i.e., predominant species), and habitat changed in light of a recent record-shattering flood and the removal of a small dam, and place those changes within the context of other stressors documented within the 50 year study period. The record-shattering flood changed the stream and riparian habitat and, along with the dam removal, the turtle assemblage. In the short term, G. geographica and other turtle species within the assemblage, with the exception of Sternotherus odoratus, either exhibited positive or neutral impacts from the flood. We conclude that turtle species adapted to lotic habitats can cope with extreme flooding if their populations are secure prior to flooding and if the riparian and stream habitats are intact. However, as more threats simultaneously impact turtle populations, we expect fewer populations to be able to withstand such additional stressors. Within the context provided by the fifty year study period, we found that harvesting had more immediate negative impacts on the G. geographica population than did flooding.
TL;DR: The effects of grazing by goats as well as cattle and horses on forest structure and spatial distribution of a dominant tree species in Coahuila, Mexico, an area affected by overgrazing and with problems of desertification is analyzed.
Abstract: Increases or decreases in grazing cause significant disturbances in natural and managed forests. Indeed, grazing impacts can be on par with habitat destruction, exotic species invasion and fire. Grazing can produce changes in the diversity of native and exotic species as well as in functional plant groups at community and ecosystem levels. Unfortunately, overgrazing is a common occurrence in many plant communities, increasing erosion risks, land degradation and plant invasion. We analyze and quantify the effects of grazing by goats as well as cattle and horses on forest structure and spatial distribution of a dominant tree species (Pinus cembroides) in Coahuila, Mexico, an area affected by overgrazing and with problems of desertification. We also assess the influence of other forest variables that may be affected by cattle grazing, such as infestation by Tillandsia recurvata (an atmospheric epiphytic bromeliad) on P. cembroides. The study site is a protected area of 45,000 ha in the Sierra of Zapaliname (Coahuila, Mexico). In this area, grazing is considered a traditional and essential activity as the local economy depends on it. Eight plots (900 m2) 100 m apart were set up over a control site that had been grazed by cattle and equines for at least the last 100 years, while another eight plots (also 100 m apart) were established in an area that had excluded grazing for 25 years. Tree species composition and forest structure were analyzed in the plots, as well as other relevant variables, like T. recurvata infestation. The number of tree species (DBH≥2.5 cm) differed significantly in control (6) vs. exclusion areas (11), with higher values in the latter. In addition, infestation of T. recurvata was found to be significatively higher in plots where grazing occurred. Spatial analysis of the tree distribution did not reveal any specific patterns related to either grazed or exclusion areas, and neither were there significant differences in species composition. For saplings (>50 cm high and
TL;DR: The hummingbird specialization was related to the bill length and found that the migratory status, particularly the altitudinal migratory species, was associated with the hummingbirds' altitudinal migration.
Abstract: Comparing ecological networks along environmental gradients can enable a better understanding of the environmental filtering and coexistence mechanisms that determine community assembly. In the present study, we assessed hummingbird-plant network metrics at three sites along an altitudinal gradient in the Sierra Madre Occidental corresponding to tropical forest (148 and 289 m a.s.l.), ecotone (1131 and 1423 m a.s.l.) and pine-oak forest (1800 and 2218 m a.s.l.). We evaluated variation in the specialization (d’) of the hummingbird species and their visited plant species across altitude. We determined if hummingbird species inside the modules of the general network were separated by biogeographical origin, migratory behavior, or morphology. We assessed whether the role in the modular partition of hummingbird and plant species in the general network was related to traits of species. Finally, determined which traits were associated with the importance of different species within the network. We recorded 1050 interactions between 20 species of hummingbirds and 64 species of plants. We found that network metrics in the ecotone differed from other sites, reflecting the convergence between temperate and tropical forest flora and the midpoint in hummingbirds' altitudinal migration. As in previous studies, we found that hummingbird specialization was related to the bill length and found that the migratory status, particularly the altitudinal migratory species, was associated with the hummingbird specialization. The abundance of hummingbird species and flowers (ornithophilous and non-ornithophilous) along the gradient plays a central role in the importance within the network and in the formation of the modules.
TL;DR: Differences in community-wide patterns of interference with seeds of rainforest trees, between fragments and continuous forest, were tested and whether these differences were associated with changes in the seed predator communities were assessed.
Abstract: Rainforest fragmentation has large impacts on ground-active vertebrates, including granivorous mammals (e.g., rodents), and birds. We tested for differences in community-wide patterns of interference with seeds of rainforest trees, between fragments and continuous forest. We also assessed whether these differences were associated with changes in the seed predator communities. Seeds of 20 locally-common tree species were deployed at experimental stations in 12 rainforest sites (six continuous forest and six fragments) across an agricultural landscape in subtropical Australia, where vertebrates rarely cache seeds. Eleven species had small seeds (
TL;DR: Evidence for the coupling relationships between leaf economics, hydraulic, and shade-tolerant traits among co-occurring individuals is provided and it is highlighted that bivariate trait relationships based on large-scale interspecific surveys may be the opposite of that within-community scales.
Abstract: Leaf economics, hydraulic, and shade-tolerance traits involve different resource-use strategies, and are critical for interactive plants, yet it remains unclear whether co-occurring individuals modulate the coupling relationships between these trait dimensions. To address this knowledge gap, we measured four leaf economics, five hydraulic, and two shade-tolerant traits in leaf and wood tissues across 90 individuals from 26 tree species in two subtropical forests in Eastern China. Confirmatory factor analysis (CFA) and Principal Component Analysis (PCA) were employed to explore multi-trait relationships. With respect to leaf economics traits, leaf nitrogen concentrations were positively associated with leaf stomatal density and conductance, leaf-specific hydraulic conductivity, and twig vessel diameter. However, leaf phosphorus concentrations were negatively associated with leaf-specific hydraulic conductivity. The specific leaf area was negatively associated with the light exposure index, light saturation point, and leaf Huber value. Regarding hydraulic traits, twig vessel diameters were positively correlated with the light saturation point and light exposure index. Stomatal conductance was positively associated with the light saturation point, whereas leaf-specific hydraulic conductivity was positively associated with the light exposure index. The first two PCA axes explained 54.23% of the total trait variation. The first axis of the multi-trait variation was mainly explained by leaf habits and represented the trade-offs between acquisitive hydraulic economics and cheap leaf economics. The second axis of the multi-trait variation was mainly explained by plant growth form, and defined the trade-offs between weak shade tolerance and cheap leaf area construction. In conclusion, our results provide evidence for the coupling relationships between leaf economics, hydraulic, and shade-tolerant traits among co-occurring individuals. This study also highlights that bivariate trait relationships based on large-scale interspecific surveys may be the opposite of that within-community scales.
TL;DR: In this paper, the authors summarized current knowledge on litter decomposition above the treeline in alpine regions worldwide and identified: I) factors that have been studied in great detail, II) factors which have been less intensively investigated, III) geographical regions and IV) factors with consistent or inconsistent effects on decomposition.
Abstract: Litter decomposition is a key driver of ecosystem processes and carbon cycling. Decomposition rate is influenced by numerous factors, such as temperature, humidity, litter properties, soil properties, and properties of soil fauna/microbial communities. The aim of this review was to summarize current knowledge on litter decomposition above the treeline in alpine regions worldwide and identify: I) factors that have been studied in great detail, II) factors that have been less intensively investigated, III) geographical regions that have been less well studied, and IV) factors with consistent or inconsistent effects on decomposition. The review showed inconsistent results for all factors covered by two or more studies regarding their effect on decomposition rate (positive, negative, no effect), usually a result of interactions between factors. Studies examining one or several factors in the physical environment (i.e., altitude, experimental warming, microclimate, snow cover and soil moisture) were most common, while studies on different aspects of resource quality were the second most common. The impacts of trophic interactions on soil microbes and fauna were less frequently studied. Europe and Asia were the best-represented regions, in terms of number of studies and geographical distribution, while there were no studies from Africa and very few from South America and Australia. North American studies were all from Colorado, and those from Asia were all from China. In order to obtain better global representation, there is a need for studies in Africa, South America, and Australia. There is also a need for more studies to explain the large variation in responses of litter decomposition rates to different influencing factors in alpine environments. Future research should focus on interactions between different factors and on experiments testing specific relationships, such as the potential interaction between temperature and soil moisture and its effect on litter decomposition above the treeline in alpine regions.
TL;DR: In this article, the authors systematically searched for studies on the distribution of Ficus spp. in Africa and their frugivore interactions together with the effects of land-use changes up until 2021.
Abstract: Land-use change is one of the greatest threats to biodiversity. It is predicted that conversion of land and habitats will increase rapidly over the next few decades in Africa. Over the years, these changes potentially reduced the capacity of ecosystems to sustain food production for vertebrates. Ficus species (Moraceae), commonly known as figs, occupy diverse habitats and typically produce large numbers of nutritional fleshy fruits that are important to frugivores. However, a decline in Ficus spp. distribution because of land-use changes may negatively affect frugivores and their ecosystems (e.g. via seed dispersal). We systematically searched for studies on the distribution of Ficus spp. in Africa and their frugivore interactions together with the effects of land-use changes up until 2021. Our search resulted in 70 eligible papers. A total of 124 Ficus spp. were recorded across 30 African countries representing approximately 56% of the African countries. Cameroon had the highest record of 63 species, while Benin, Burundi, Ghana, and Rwanda had two, the least number of Ficus spp. recorded. East Africa had the highest Ficus spp. richness recorded (96 species), followed by southern Africa (74 species), Central and Northern Africa (72 species), and West Africa with the least (31 species) recorded. Information about the effect exerted by anthropogenic land-use changes on Ficus-frugivore interaction in Africa was limited. However, research has been conducted on the impact of anthropogenic land-use changes on plant-frugivore and frugivore feeding ecology. Ficus spp. fruit were identified as significant in the diets of various frugivores across Africa, as it is found globally. However, it is essential to understand the impacts of anthropogenic land-use changes on the mutual interaction between frugivores and Ficus spp. and the attendant consequences for ecosystem service provision.