Showing papers in "Acta Oecologica-international Journal of Ecology in 2020"

Soil aggregation, ecosystem engineers and the C cycle

Abstract: Soil aggregation and its effects on soil C storage have been addressed in thousands of research articles over the last 40 years. Research has been mostly focused on the resistance of aggregates to mechanical disruption and the role of organic matter in aggregate stabilization. On the other hand, relatively little attention has been paid to identifying the microbial, plant root and macro-invertebrate actors and physical processes that continuously create and destroy aggregates. The sum and dynamics of these processes determines the ability of soils to store and conserve C. Understanding the interactions between aggregation dynamics and C transformations in soils therefore requires a precise identification of the agents that produce aggregates and knowledge of the rates of formation and persistence in the pools thus identified. We propose to separate macro-aggregated components of different, physicogenic and biogenic origins from non-macro-aggregated soil on a morphological basis, using a simple visual technique. The specific biological or physico-chemical agent which produced each individual macro-aggregate can then be determined using Near Infrared Spectroscopy (NIRS). A general description of the distribution and quality of organic matter among the different groups of macro-aggregates can be made. Simple soil re-aggregation or dis-aggregation tests conducted in field conditions further measure the production of different macro-aggregates with time and their mean residence times in the studied soil. Respirometry measurements on each recognized category of macro-aggregates evaluate the respective C losses through respiration. The methods described here will allow the dominant pathways of C flow at a given site to be characterized and possible management options to increase C storage identified. We finally discuss the different assumptions made to build this simple model and offer ways to test the methodology under field conditions.

Bee hotels host a high abundance of exotic bees in an urban context

Abstract: Bee hotels are increasingly set up by land managers in public parks to promote wild bee populations. However, we have very little evidence of the usefulness of bee hotels as tools to help the conservation of wild bees within cities. In this study, we installed 96 bee hotels in public parks of Marseille (France) for a year and followed their use as a nesting substrate by the local fauna. The most abundant species that emerged from bee hotels was the exotic bee species Megachile sculpturalis, representing 40% of all individuals. Moreover, we only detected four native bee species all belonging to the Osmia genus. More worryingly, we found a negative correlation between the occurrence of M. sculpturalis in bee hotels and the presence of native bees. One hypothesis to explain this result might be linked to the described territorial and aggressive behaviour of M. sculpturalis toward the nests built by the native fauna. This study raises the question about the usefulness of bee hotels for the conservation of native bees especially within cities harbouring high abundance of exotic bees. We provide here concrete advices to land managers to build bee hotels that can both host native bees and prevent the installation of M. sculpturalis.

Land cover composition, local plant community composition and honeybee colony density affect wild bee species assemblages in a Mediterranean biodiversity hot-spot

Abstract: Identifying environmental drivers which structure wild bee species assemblages appears essential in a context of worldwide pollinator decline. During a two-year survey, we studied wild bee species assemblages in an 85km2 protected area dominated by Mediterranean scrubland, the Calanques National Park, located in southern France. Our objectives were (i) to assess the composition of the wild bee species assemblages, and (ii) to explore the effect of a) land cover composition (anthropogenic zone, low scrubland, forest and rocky land cover), b) local plant community composition, and c) honeybee colony density on wild bee species assemblages. On 17 circular 100m2 plots, we collected 541 specimens belonging to 87 wild bee species. We found that large bee species were significantly influenced by land cover composition within a 1000m radius. More specifically, we observed that the presence of a diversified land cover composition within a 1000m radius maximized large wild bee species richness, whereas large bee abundance and richness were negatively affected by honeybee colony density. Small wild bee species were structured by the local plant community composition within 100m2 plots and by land cover composition within a 1000m radius. Their occurrence were related to the local composition of plants growing on deep soils in scrublands. The Calanques National Park, which is the only European park located at the interface with a large city and consequently suffers from anthropic pressure, encompasses several types of land cover which are beneficial for a wide diversity of bees. However, we would like to raise awareness among park managers regarding beekeeping activities within this territory which includes diverse types of land cover favorable for wild bee species.

Effects of a native earthworm species (Amynthas morrisi) and Eisenia fetida on metal fractions in a multi-metal polluted soil from South China

Abstract: The effects of the native species Amynthas morrisi and the composting earthworm Eisenia fetida were evaluated on the forms of Zn, Cd, Pb and Cu in a long-term contaminated Chinese soil, with and without added organic matter (OM), in a 60-day laboratory experiment (25 °C field capacity). Four metal fractions were extracted using a sequential procedure: water-soluble exchangeable and carbonate-bound fraction (WAEX), Fe and Mn oxides fraction (FMOX), organic compounds (ORGA), and residual non-extractable fraction (RESI). The sum of available fractions (AVA = WAEX + FMOX + ORGA) and the total contents of the surface casts and non-ingested soil were calculated. In all treatments, all casts of the two earthworm species had higher pH and DOC (Dissolved organic carbon) contents and lower Eh values than those of their respective controls. Amynthas morrisi casts contained higher concentrations of available forms (AVA) of Cd (+84.1%) and Zn (+39.9%) and lower concentrations of available Cu (−10.1%) than those in the control soil (P

Direct and indirect effects of elevation, climate and vegetation structure on bird communities on a tropical mountain

Abstract: Climate and vegetation structure are important predictors of biodiversity along mountain slopes. The drivers of elevational biodiversity gradients are not yet fully resolved. For instance, there is little understanding of how direct and indirect effects of elevation shape species communities along mountain slopes. In this study, we identify the main drivers of bird diversity along an elevational gradient spanning 2000 m in the Ecuadorian Andes. We simultaneously tested the direct and indirect effects of elevation, temperature, precipitation and vegetation structure on overall bird diversity and on frugivorous and insectivorous birds, using structural equation models (SEMs). We found that elevation was mostly indirectly associated with bird diversity, mediated via abiotic (i.e., temperature, precipitation) and biotic (i.e., vegetation structure) factors. We found consistent positive effects of temperature and vegetation structure and negative effects of precipitation on overall bird diversity and on frugivorous and insectivorous birds. In addition, elevation was directly, positively associated with insectivore richness and abundance, but not with that of frugivores. Our results show that climatic factors and vegetation structure jointly shape the richness of bird communities on tropical mountains. However, other factors, such as biotic interactions or different evolutionary histories of lowland and highland communities, may additionally contribute to elevational patterns in bird diversity. Thus, species communities across tropical mountain slopes are shaped by a multitude of abiotic and biotic factors that need to be studied simultaneously for a mechanistic understanding of patterns in biodiversity.

Herbaceous seeds dominates the soil seed bank after long-term prescribed fire, grazing and selective tree cutting in savanna-woodlands of West Africa

Abstract: The soil seed bank (SSB) is an important source of resilience for plant communities subjected to disturbances. This study aimed to identify characteristics of the SSB, its relationship with aboveground vegetation (AGV), and its significance for restoration of vegetation in West African savanna-woodlands. Data were collected from two long-term factorial experiments established in 1992 in Burkina Faso to examine the long-term ecological effects of grazing, early fire, selective tree cutting on savanna-woodland ecosystem. A total of 1920 soil samples were taken from three soil layers (i.e. 0-3 cm, 3–6 cm and 6–9 cm) and the SSB was assessed using the seedling emergence technique. The emerged seedlings were dominated by non-woody taxa. Only two woody species that were Flueggea virosa and Mitragyna inermis emerged, showing that woody species feature little in the SSB. The SSB density and richness decreased significantly with soil depth. Non-metric multidimensional scaling (NMDS) ordination indicated a lack of correspondence between the AGV and SSB. The results suggest site-specific responses to disturbance also following long-term disturbance, the SSB will be ineffective in regenerating the remnant vegetation of West African savanna-woodlands. Hence, ensuring the resilience of West African savanna woodland ecosystems will require targeted introductions (i.e. planting and seeding) of indigenous species and a reduction in on-going disturbances.

How biased is our perception of plant-pollinator networks? A comparison of visit- and pollen-based representations of the same networks

Abstract: Most plant-pollinator networks are based on observations of contact between an insect and a flower in the field. Despite significant sampling efforts, some links are easier to report, while others remain unobserved. Therefore, visit-based networks represent a subsample of possible interactions in which the ignored part is variable. Pollen is a natural marker of insect visits to flowers. The identification of pollen found on insect bodies can be used as an alternative method to study plant-pollinator interactions, with a potentially lower risk of bias than the observation of visits, since it increases the number of interactions in the network. Here we compare plant-pollinator networks constructed (i) from direct observation of pollinator visits and (ii) from identification of pollen found on the same insects. We focused on three calcareous grasslands in France, with different plant and pollinator species diversities. Since pollen identification always yields richer, more connected networks, we focused our comparisons on sampling bias at equal network connectance. To do so, we first compared network structures with an analysis of latent blocks and motifs. We then compared species roles between both types of networks with an analysis of specialization and species positions within motifs. Our results suggest that the sampling from observations of insect visits does not lead to the construction of a network intrinsically different from the one obtained using pollen found on insect bodies, at least when field sampling strives to be exhaustive. Most of the significant differences are found at the species level, not at the network structure level, with singleton species accounting for a respectable fraction of these differences. Overall, this suggests that recording plant-pollinator interactions from pollinator visit observation does not provide a biased picture of the network structure, regardless of species richness; however, it provided less information on species roles than the pollen-based network.

The apiary influence range: A new paradigm for managing the cohabitation of honey bees and wild bee communities

Abstract: There is an emerging controversy among bee biologists, land managers and beekeepers about the legitimacy of high-density beekeeping in natural protected areas due to the risks of detrimental interactions with local wild bees. The conflicting needs of wild bee conservation and productive beekeeping requires the adoption of inclusive conservation measures. The distance-based beekeeping regulation is a relevant candidate approach in that respect. It consists in increasing spacings among neighbouring apiaries so as to reduce the proportion of land cover under detrimental competition for floral resources. This approach stems from the concept of Apiary Influence Range (AIR), i.e. the distance range around apiaries within which measurements of native plant-pollinators interactions are significantly altered. The seminal study on this topic reported AIRs spanning distances of 0.6–1.1 km around apiaries. The objective of this study is to provide conservation biologists and practitioners with a roadmap to manage the coexistence between productive beekeeping and wild bee conservation, along with a formalised terminology. We first introduce the key theoretical ideas linked with the AIR. Then, we develop the associated calculation rationale to help land managers achieve their wild bee protection goals. Finally, we further provide original AIR values complementary to those available in recent literature. We believe the distance-based beekeeping regulation is in practice more tractable than setting maximal honey bee colony density rules. It may contribute to guide bee biologists and conservation practitioners towards successful inclusive bee conservation, providing the approach can be supported by a broader range of trials in various environmental contexts and using standardised terminology.

Disentangling elevational and vegetational effects on ant diversity patterns

Abstract: When aiming to assess the effects of elevation on animal diversity, many studies have been carried out in different vegetation types occurring across elevational gradients. Thus, it remains unclear if any changes observed in species richness are caused by factors directly associated with elevation or are caused by vegetation change across the gradient. Here, we disentangled the effects of elevation from changes in vegetation by assessing ant diversity patterns along an elevational gradient. We analyzed patterns of ant diversity utilizing two different sampling approaches across the elevational gradient: (1) a standardized sampling including only forest formations and (2) a non–standardized sampling including forest (low elevational bands) and grasslands (high elevational bands). We sampled ants at eight elevational bands of Atlantic Forest in Brazil, and the highest three bands were sampled at both forest and grassland habitat. We found that the two approaches produce contrasting patterns of alpha and beta diversity, but the same pattern of gamma diversity. However, in the non–standardized sampling approach, the regression analysis produced a reduced explanation of the species richness gradient and a decrease in the elevational effect size. Different patterns found in the two approaches could be due to distinct environmental conditions in these habitats. In conclusion, our results highlight the potential bias of non–standardizing vegetation type across elevational gradients when assessing elevational patterns of species diversity.

Lantana camara and Ageratina adenophora invasion alter the understory species composition and diversity of chir pine forest in central Himalaya, India

Abstract: Plant invasion has been a major threat to biodiversity and ecosystem stability. In the present study, we have estimated the effect of two invasive alien species, Lantana camara and Ageratina adenophora on the understory vegetation composition and species diversity of chir pine (Pinus roxburghii) forests in the central Himalaya. We have selected three sites in pine forests and each site was divided into three subsites i.e. non-invaded (NI), Lantana camara invaded (LI) and Ageratina adenophora invaded (AI). In each subsite, 10 random quadrats for herbs (1 × 1 m) and shrubs (5 × 5 m) were laid down. In all the study sites, native herbs and shrubs species richness, diversity, and evenness changed due to invasive species. The presence of both the invasive species caused a reduction in native understory herbs and shrubs species number by 29–40% indicating a strong effect on native vegetation. Shrub density ranged from 6720 to 9680 individuals ha−1 and 8960 to 12000 individuals ha−1 in LI and AI sites, respectively. Total shrub basal area varied between 1.64 and 2.52 m2 ha−1 in LI sites and 1.76 and 2.24 m2 ha−1 in AI sites. Shrub density and basal area in NI sites (4200–6960 individual ha−1 and 0.60–0.96 m2 ha−1) were 2–3 times lower than LI and AI sites. Higher shrub density and basal area in LI and AI sites altered the vegetation composition and diversity of understory vegetation in pine forests. The dominance of invasive species also altered the soil physico-chemical properties. Their interrelationship among species assemblage, study sites and environmental variables showed the adverse impact of invasion on native species. This depletion of native flora is worrisome for both ecological as well as socio-economical perspectives and needs urgent attention of forest managers and policymakers.

Functional traits vary among fleshy-fruited invasive plant species and their potential avian dispersers

Abstract: Habitat fragmentation has a multitude of negative effects on biodiversity, including the facilitation of alien plant invasion. Of concern in South Africa is the spread of fleshy-fruited invasive plant species, which in many places are replacing indigenous vegetation in frequently disturbed and fragmented habitats. The availability of dispersers is among the most important factors for the successful invasion of fleshy fruited invasive plant species. Dispersers differ in their dispersal capacity, and the success of frugivore dispersed plants depends both on animal and plant traits. Here, we used the functional traits of fleshy-fruited invasive plants to test for specific associations with avian functional traits in Indian Ocean Coastal Belt Forests, KwaZulu-Natal Province, South Africa. We predicted that fleshy-fruited invasive plant species that were more likely to persist in disturbed Indian Ocean Coastal Belt Forests were small-seeded, open habitat species with longer fruiting period lengths. The use of multivariate analyses showed that avian seed dispersers and fleshy-fruited invasive plant species differed in the functional traits between species with each group (i.e. plants and avian dispersers) that were important for seed dispersal. For fleshy-fruited plants, morphological traits (seed size, fruit size) and phenological traits (fruiting period length) were more variable between the species. For avian species, the variation was in their morphology (body size, gape width, bill length), abundance and habitat specificity. As predicted, avian species that were potentially dispersing invasive plants were forest generalist and relatively abundant species persisting in the fragmented forest. Fleshy-fruited invasive plant species that were predicted to be effectively dispersed were small-seed, open habitat species with longer fruiting length including lantana (Lantana camara), white mulberry (Morus alba), Brazilian pepper (Schinus terebinthifolius) and bugweed (Solanum mauritianum). Overall, our study showed that easily measured traits were important for understanding forest invasion dynamics and give insights to management strategies that can be developed to minimise further infestations.

Foraging efficiency of white stork Ciconia ciconia significantly increases in pastures containing cows

Abstract: Recent changes in agriculture have had a very strong impact on avian populations, but detailed mechanistic explanations are scarce. Some proposed solutions to avian declines can be complicated because responses are not linear. For example, abandoning pasture management can be detrimental to many open-nesting birds, but also to some others, because livestock perform ecosystem engineering, changing sward height and creating microhabitats for invertebrates, as well as for insectivorous mammals. Both these features affect the foraging efficiency of birds, for example white stork Ciconia ciconia. We studied the foraging activities of storks in the presence and absence of grazing cows, and we show that in extensive farmland in NE Poland, the presence of cows has a highly significant effect on stork foraging efficiency (in our study area mainly catching insects), which may be crucial to improving breeding success. Our results may also be important from a practical point of view. In white stork recovery projects where supplementary food is offered to storks (e.g. chicken and fish provided on feeding platforms) we believe that establishing extensive cattle pastoralism would be better from an ecological as well as from an aesthetical viewpoint.

The impact of pollen quality on the sensitivity of bumblebees to pesticides

Abstract: With 2000 species currently recorded in Europe, bees are a highly diversified and efficient group of pollinating insects. Their decline could therefore lead to a risk for ecosystems functioning and crop yields. The drivers of this decline have been well documented in Europe and involve multiple factors such as pesticides, pathogens, poor nutrition, climate change, and their respective interactions. For pesticides, there is a lack of information concerning the impacts of exposure when the bees have access to pollen diet of different nutritional quality (e.g. variation in sterol and protein content). We performed bioassays on nine groups consisting of 10 Bombus terrestris microcolonies (i.e. queen less colonies) each in a fully crossed experiment including controls without pesticide, two different doses of neonicotinoid imidacloprid (2 and 20 μg/L) and three pollen diets (i.e. Salix mix, cellulose-diluted Salix mix and cellulose-diluted Salix mix enriched with soy protein). All colonies were fed ad libitum with syrup and pollen. We measured the collection of pollen and syrup, the brood mass and the pollen efficacy (ratio of brood mass/pollen) at the end of the experiment. All these variables were affected by the imidacloprid doses, especially pollen efficacy, which was two and 10 times lower than the control for the 2 and 20 μg/L treatments, respectively. As expected, pollen efficacy was also affected by the pollen diet. However, when exposed to imidacloprid, the three different pollen diets did not affect micro-colonies performances. Overall, we show that diet quality does not affect sensitivity to imidacloprid exposure. It seems therefore that the negative effects of imidacloprid exposure cannot be compensated for by a pollen diet of high quality.

Fruiting phenology and consumption of zoochoric fruits by wild vertebrates in a seasonally dry tropical forest in the Brazilian Caatinga

Abstract: This study aimed to describe and evaluate the fruit phenology of zoochoric plants and the use of this resource by wild vertebrates in a seasonally dry tropical forest in the Furna Feia National Park, an area of Brazilian Caatinga. Specifically, we described the seasonal variation in fruiting of zoochoric species and evaluated the influence of rainfall intensity on the seasonal variation of fruiting, along with the relative importance of each fruit producing species in the diet of medium- and large-sized vertebrates by analysis of fecal samples. Monthly expeditions to the study area occurred between January 2013 and June 2018, during which we monitored the phenology of 643 plants, belonging to 11 species, and collected vertebrates fecal samples. Sideroxylon obtusifolium, Cereus jamacaru, Ziziphus joazeiro, Commiphora leptophloeos and Bromelia laciniosa fruited during the rainy season, while Myracrodruon urundeuva, Licania rigida, Cissus sp. and Maytenus rigida fruited during the dry season. Phoradendron quadrangulare and Cynophalla flexuosa presenting lower seasonality in the fruiting throughout the year. The rainfall intensity influenced the fruiting of more than 50% of the zoochoric plant species, corroborating the prediction of the existence of a relationship between rainfall intensity and fruiting for Caatinga zoochoric plants. Sixteen plant species were identified in 294 fecal samples, suggesting medium- and large-sized vertebrates act potential seed dispersers of 12 plant native species. Future conservation strategies for Caatinga forests should prioritize the protection of multiple plant species to ensure fruit availability throughout the year.

Plant-pollinator interactions on green roofs are mediated by substrate characteristics and plant community composition

Abstract: Green roofs can support pollinator communities in cities. However, little is known about the influence of green roof characteristics such as substrate and vegetation type on the abundance and diversity of attracted pollinators. Here we aimed to assess how green roof design impacts their attractiveness to pollinators. Using mesocosms on a rooftop in Paris (France), we studied the impact of two substrate types, two substrate depths (10 and 30 cm) and either monocultures or mixtures of 5 plant species on plant pollinator interactions. In the case of mixtures, we also tested the effect of substrate type (natural soil vs. artificial substrate). We counted the number of floral units and recorded the visits by pollinators once a week from mid-June to mid-August. The pollinator assemblage visiting plant communities included 4 functional groups of pollinators: domesticated honey bees, bumble bees, solitary bees and syrphid flies. Effects of treatments on pollinator community composition were variable and plant species dependent. Deep monoculture treatments resulted in the highest number of floral units and visits. Although plants grown on natural soil had less floral units than on artificial substrate, both treatments resulted in a similar number of visits. This paper provides evidence that plant-pollinator interactions on green roofs are modulated by substrate type, substrate depth and plant community. We suggest that combining plant species with diverse flowering morphologies and phenologies can enhance pollinator diversity. When possible, increasing substrate depth can result in higher levels of attractiveness.

Different responses of dung beetle diversity and feeding guilds from natural and disturbed habitats across a subtropical elevational gradient

Abstract: Understanding the effects of natural and anthropogenic processes that drives biodiversity is urgently needed to improve conservation strategies at the landscape scale. Although natural drivers on altitudinal gradients have been well studied, the concatenated effect of habitat disturbance across different altitudes over biodiversity is still poorly known. We aimed to test the effect of habitat transformation on assemblage metrics of dung beetles across an altitudinal gradient (between 0 and 3400 m.a.s.l.; 18 elevational bands). Our results highlighted four main findings: (i) dung beetle forests or pastures specialized species changed their habitat specificity depending on the elevation range; (ii) a hump-shaped pattern of dung beetle diversity at intermediate elevations was found both in forests and pastures; (iii) species turnover was the main component of β diversity in both forest and pastures; (iv) presence of crops and human settlements across elevational gradient influenced changes the taxonomical and feeding guild composition of dung beetle assemblages, but these effects were elevation-site-dependent. These results suggest that the impacts of habitat disturbance on beetle assemblages caused by humans’ activities on mountains are spatial site dependents. We highlight the importance of understanding the effect of environmental disturbance in mountain ecosystems using a wide range of assemblage metrics. This research serves as basis for the development of efficient conservation strategies to protect species and ecosystem functions in these fragile environments.

Nematode metabolic footprints, ecological and functional indices in tropical maize-beans agro-ecosystems under different farming practices

Abstract: Maize and beans contribute significantly to food security in Kenya. Farming practices used in production of these crops may affect nematode community assemblages and influence agricultural productivity. Information on response of nematofauna, particularly free-living nematodes, under various agronomic practices in Kenyan maize-beans intercrop is scarce. This study reports on the effects of farming practices on nematode community dynamics, ecological and functional indices, nematode metabolic footprints, and predator-prey relationship in maize-beans cropping systems in Mwea, Kenya. The field trials were set up in two seasons in a randomized complete block design with each treatment consisting of four replicates. The treatments included cow manure plus chemical fertilizer (CmDCF), cow manure plus wood ash (CmWa), cow manure combined with wood ash plus fertilizers (CmWaF), chemical fertilizers only (DNF) and unamended controls. Soil samples were collected at 0–20 cm depth at bimonthly intervals during 2018–2019. During the two seasons, 54 nematode genera were identified. Cephalobus, and Heterocephalobus (bacterivores), Labronema (omnivore) and Nygolaimus (predator) were abundant in CmDCF, CmWa, CmWaF, and DNF while Aphelenchus and Aphelenchoides (fungivores) were dominant in all treatments. Principal response curve analysis showed that CmWaF significantly reduced the population of Helicotylenchus, Scutellonema and Rotylenchulus during the 2nd and 4th month in the second season. Renyi diversity analysis indicated that CmWaF had higher diversity of omnivores while functional metabolic footprints categorized it as structured in both seasons. Predator-prey analysis suggested that CmWa and CmWaF have the potential to provide suitable conditions for predators, target prey and amplifiable prey biomass. This study provides an insight on the implication of farming practices, on nematode abundance and soil food web in two economically important crops in Kenya. It also provides a basis for exploring the potential role of organic amendments containing cow manure in control of plant parasitic nematodes in maize-beans cropping systems.

Sudanian versus Zambezian woodlands of Africa: Composition, ecology, biogeography and use

Abstract: The Sudanian woodlands (SW) and Zambezian woodlands (ZW) of Africa cover two extensive vegetation zones in Africa. The main question is how similar or different are their woodlands. This paper aims to synthesize available information on woodlands of the Sudanian (SR) and Zambezian (ZR) regions in terms of: i) their floristics and ecology, ii) main drivers of change, iii) their socio-economic relevance to local populations, and iv) how resource use affects the main drivers. This synthesis deals with 141 publications, including 94% research articles and books on Sudanian and Zambezian woodlands of Africa. Google Scholar's search engine were used. Inclusion criteria comprised the geographical focus (Sudanian and Zambezian regions), the ecosystem type (woodland), and the type of information reported in the studies (ecology, socio-economic and biogeography aspects). The overall results were categorized as addressing either ecological or socio-economic aspects of woodlands. The SW and ZW share a number of families, genera and species. The ZR counts at least 8500 plant species, of which 54% are endemic, while there are possibly no more than 2750 plant species in the SR. Three distinct woodland types are ecologically important and clearly differentiated in the ZW. However, combined effect of the wide tolerances of the species and the gradual change in the climate in the SZ, makes it difficult to recognize distinct woodland systems. The presence of great rifts and swells in the Zambezian part of Africa, explain in part the difference in the vegetation composition and the high diversity and plant endemism in the Zambezian zones. In both Regions, use of woodland and the associated ecological impacts are quite similar. Both biogeography and land use change explain the vegetation differences between the two regions. Knowledge of factors underlying vegetation adaptations and change provide a basis for sustainable resource use through integrated multiple-use systems.

Similitudes and differences between two closely related Ficus species in the synthesis by the ostiole of odors attracting their host-specific pollinators: A transcriptomic based investigation

Abstract: Flower odor is often essential for attracting pollinators, and this is especially true for species-specific mutualism such as the one between Ficus species and their pollinating wasps. Receptive figs emit a stage and species specific odor composed of a mix of volatile organic compounds (VOC) that is attractive to their pollinators. Histological studies suggest that the ostiolar bracts are the main locus of fig floral VOC synthesis. To confirm a major role of the ostiole in VOC synthesis, detect the genes involved in VOC synthesis and analyze differences between closely related species, we compare the transcriptomes of pre-receptive and receptive figs of two closely related species, F. hirta and F. triloba. The two species presented similar numbers of expressed genes and similar annotation, classification results, and their up-regulated unigenes belonged to similar biosynthetic pathways. However, phenylpropanoid and terpene synthesis were the main enriched VOC pathways in receptive figs of F. hirta while terpene and jasmonate synthesis were the main enriched VOC pathways in F. triloba. The shift in gene expression between pre-receptive and receptive figs was much more marked in the ostiolar bracts than in the flowers of F. hirta, and in the fig wall, confirming an important role of the ostiole in receptive fig odor emission. Only one unigene directly involved in VOC synthesis presented signatures of positive selection, further supporting that the source of interspecific receptive fig odor differentiation is based on gene regulation rather than on gene differentiation. Regulation based receptive fig odor differentiation between species suggests a potential for rapid evolution of this interspecific barrier.

Contrasting effects of herbivore damage type on extrafloral nectar production and ant attendance

Abstract: The ant-plant mutualism mediated by extrafloral nectaries (EFNs) is based on the provision of extrafloral nectar (a sugar-rich liquid) in exchange for ant defense against herbivores. The extrafloral nectar production can vary depending on the intensity or types of leaf damage caused by different mouthparts of insect herbivores (i.e., sucking or chewing insects). However, it is poorly known how the type of herbivore damage changes the outcomes of tri-trophic interactions. Here, we address how the damage inflicted by different herbivore groups affects extrafloral nectar production and ants’ attendance and aggressiveness. Through an experimental field study, we tested whether the type of leaf damage, sucking or chewing, changes extrafloral nectar volume and sugar concentration, and subsequently ant composition and behavior. We evaluated the extrafloral nectar production and ant attendance and aggressiveness before and after simulated herbivory in Qualea parviflora (Vochysiaceae), a Brazilian savanna EFN-bearing plant. We found that only plants with sucking damage increased the sugar concentration of their extrafloral nectar, only plants with chewing damage increased ant abundance, and surrogate herbivore predation differed before and after simulated herbivory only for sucking damage. We provided the first evidence that the type of damage can influence ant aggressiveness via changes in extrafloral nectar production, translating to changes in the outcomes of this ant-plant mutualism. Ultimately, studies should consider the effects of herbivore damage type when studying insect-plant interactions.

Orchid-pollinator network in Euro-Mediterranean region: What we know, what we think we know, and what remains to be done

Abstract: Facing the threat of global change, there is an urgent need to document our current knowledge about the interactions between plants and their pollinators, especially for species with specialized pollination strategies. We review orchid-pollinator networks in the Euro-Mediterranean region by providing an overview and a critical analysis of our current knowledge on pollination interaction. This review is organized in three parts: what we know, what we think we know and what remains to be done. Firstly, by relying on the recent orchid-pollinator network analyses, we investigate in detail what we know in terms of pollinator preferences as well as in terms of orchid pollination strategies. Even if at least one pollinator species is recorded for about half of the species of orchids in the Euro-Mediterranean region, we show that our knowledge of the orchid pollinator interaction stays largely imperfect. Secondly, we have identified several biases in what we think we know about orchid-pollinator interactions, by i) examining potential mistakes about species identification, but also potential biases induced by preconceived beliefs about the highly specialized pollination of Ophrys and also about the expected abundance of pollinators on nectar-producing orchids and ii) revealing a novel and promising research avenue concerning the sex of the pollinator and the strategy used by orchids to attract their pollinators. Thirdly, we have identified what remains to be done to give priority to the Euro-Mediterranean countries and orchid taxa which are still neglected or insufficiently studied. Finally, we propose several dos and don'ts to improve our knowledge of orchid-pollinator network by using a structured approach that is common to all field naturalists and scientists working on this fascinating topic.

Phylogenetic α- and β-diversity elevational gradients reveal consistent patterns of temperate forest community structure

Abstract: Phylogenetic data on species relatedness have increasingly involved in the analysis of community assembly mechanisms within the ecophylogenetic framework. Null-model analysis can detect patterns of phylogenetic clustering and overdispersion, corresponding to the leading roles of environmental filtering and biotic interactions in community assembly, respectively. Elevational gradients in montane communities are ideal systems for studying phylogenetic structure due to the existence of steep environmental gradients over short geographical distances. We analyze patterns of phylogenetic community structure in a montane temperate forest on Donglingshan Mountain, Beijing, China. We performed analysis based on both abundance-weighted and non-weighted α- and β-diversity metrics for three vegetation layers. We found layer-specific gradients of phylogenetic community structure. α- and β-diversity provided a consistent perspective on community assembly mechanisms. The elevational patterns of phylogenetic structure differ for woody and herbaceous plants. There is a linear transition from phylogenetic overdispersion at low elevations to phylogenetic clustering at high elevations in the tree and shrub layers. The herb layer is characterized by U-shaped relationships for abundance-weighted phylogenetic structure metrics. Low and high elevations are characterized by phylogenetic overdispersion, while mid-elevations show wide variation with no clear phylogenetic pattern. The greatest discrepancy between woody and herbaceous plants takes place at high elevations, where we observed phylogenetic clustering in the tree layer and overdispersion of the herb layer. This implies that different processes may determine the assembly of the species composition for woody and herbaceous species. We highly suggest that the combination of both phylogenetic and trait-based analyses can shed new light on our understanding of community assembly rules.

Does N deposition mitigate the adverse impacts of drought stress on plant seed germination and seedling growth

Abstract: Large amounts of nitrogen (N) enter ecosystems via N deposition. The increased drought stress has incurred serious threats to plant seed germination and seedling growth (SGe-SGr). It is significant to characterize the combined impacts of N deposition and drought stress on SGe-SGr of plants to enable a further explanation of the response mechanism of SGe-SGr to N deposition and drought stress. This study aims to explore the combined impacts of N deposition with a concentration gradient and drought stress (mimicked using PEG 6000) with different levels on SGe-SGr of wheat. N treatment raises seedling growth of wheat mainly due to the increased levels of available N and the decreased level of peroxidation of the cell cytoplasm membrane of wheat. Drought stress declines SGe-SGr of wheat mostly due to the progressively enlarged osmotic pressure triggered by water deficit and the advanced level of peroxidation of the cell cytoplasm membrane of wheat. N treatment regardless of the concentration dramatically mitigates the adverse impacts of drought stress on seedling growth of wheat. This may be owed to the improved competitive ability for sunlight acquisition and leaf photosynthetic area via the deactivation of nutrition limits (wheat can absorb more N nutrients and improve its drought resistance ability) implemented by N addition. This may also due to the down-regulated level of peroxidation of the cell cytoplasm membrane of wheat under the combined N and drought stress. However, the combined treatments of the high level of N supply and light drought stress decline seed germination of wheat. This may be due to the promoted osmotic pressure contributed by the high level of N supply under water deficit. Thus, N deposition mitigates the adverse impacts of drought stress on seedling growth of wheat but aggravates the adverse impacts of drought stress on seed germination of wheat mostly.

Are native nectar robbers against the alien? Effects of floral larceny on the reproductive success of the invasive yellow bells (Tecoma stans, Bignoniaceae)

Abstract: Floral larceny is expected to impact negatively the female fitness of alien plant species; however, the effects of nectar robbers are context-dependent and sometimes neutral. In this study, the effect of nectar robbers on the female fitness of the ornamental and invasive yellow bells, Tecoma stans (L.) Juss. ex Kunth (Bignoniaceae), was tested in two typical exotic habitats in northeastern Brazil: urban area and rural land. In order to quantify the intensity of floral larceny and identify the flower-visiting insects on T. stans, we sampled robbery in pre-anthesis flowers, and the frequency of illegitimate and legitimate visits in both sites. We also described the nectar-secreting pattern, and conducted experiments to test the effect of nectar robbing on plant female fitness. Our results indicated that nectar robbers provided neutral rather than negative impact on fruit and number of seeds in T. stans, mediated by the continuous nectar secretion and low natural fruit set. The populations of both habitats differed in the intensity of nectar robbing and pollinator activity. The main nectar robbers were stingless bees (Meliponini, Apidae) and carpenter bees (Xylocopini, Apidae). We found a higher predominance of primary and secondary nectar robbers in the urban area than in the rural environment. In addition, urban T. stans faced up to higher resource theft (nectar and pollen) and lower fruit set. This pattern may not be controlled by nectar production since the secretion pattern was similar between habitats. Nevertheless, T. stans may spread throughout rural environments with more opportunity to interact with pollinators, instead of nectar robbers.

2D or not 2D? Three-dimensional home range analysis better represents space use by an arboreal mammal

Abstract: For animals which utilise vertically distributed habitat resources, home ranges quantified in two-dimensions (2D) likely misrepresent space use and constrain interpretations of species' ecology and behaviour. Three-dimensional (3D) home range estimation has proved useful for understanding space use over relatively large vertical ranges (e.g. 100's of meters), yet none have applied a 3D approach to describe space use over narrower vertical ranges (e.g. meters or 10's of metres) typical for many arboreal animals. This study demonstrates 3D home range estimation for the arboreal western ringtail possum (Pseudocheirus occidentalis) using temporally resolute locations (15 min intervals) of five radio collared animals. We hypothesised that, due to the use of vertically distributed habitat resources, 3D home ranges would be more complex, spanning a range of heights, and would subsequently be larger in size compared to those estimates derived from typical 2D analysis. A comparison of 50% (core) and 95% (total) 2D kernel density and 3D kernel density utilisation distributions reveal structurally complex home ranges that span the entire vertical range of vegetated habitat. Estimates of the total 3D home range size were significantly greater than those derived from 2D analysis, and the difference in size was positively related to the vertical range of available habitat. This study establishes that 3D home range analysis can reveal information on vertical space use of arboreal species over relatively small vertical ranges, and is likely to be valuable in understanding the use and identification of key habitats and resources, as well as interactions among sympatric species.

Cave lithology effect on subterranean biodiversity: A case study in quartzite and granitoid caves

Abstract: Physical features and lithology variations contribute to promoting changes in faunal composition and richness between caves in Neotropics. Cave lithology effects on biodiversity were reported to iron ore caves in Brazil, however, it is less clear to granitoid and quartzite caves. Hence, based on these two kinds of rocks we correlate invertebrates species richness and composition with some cave features (lithology, the distance between caves, cave extension, number of entrances, entrance size, environmental stability, and altitude). Overall, 1,027 invertebrate species were recorded in 50 sampled caves. From this total, 11 obligate cave species were found. Invertebrate assemblages showed considerable turnover between caves and rock types with a strong contribution of replacement component of beta diversity. Replacement influence was greatest in quartzite caves mainly because of altitude and distance among caves. Furthermore, richness was determined by cave extension in both lithotypes, although this relationship was much more pronounced for the granitoid caves, which contradicts previous studies. The granitoid caves studied here are predominantly structured by stacked blocks with macro and meso anastomosed subterranean spaces that provide an extensive network of interstices with structural characteristics similar to shallow subterranean habitats that may increase in habitat availability and species richness. The study highlight that the lithology-mediated effects of cave extension on richness must be considered for quartzite and granitoid in the ecological and conservational proposal. Furthermore, altitude and distance among caves were important elements determining invertebrate composition.

Bat-fruit networks structure resist habitat modification but species roles change in the most transformed habitats

Abstract: Species do not function as isolated entities, rather they are organized in complex networks of interactions. These networks develop the ecological processes that provide ecosystem services for human societies. Understanding the causes and consequences of changes in ecological networks due to landscape modification would allow us to understand the consequences of ecological processes. However, there is still few empirical data on the effects of network characteristics on the loss of natural environments. We investigated how bat–fruit networks respond to three landscapes representing the gradient of modification from pre-montane forest to a heterogeneous agricultural landscape in the Colombian Andes (continuous forests, forest fragments, and crops). We found that forest contained smaller bat–fruit networks than forest fragments and crops. Modified landscapes had similar ecological network structures to forest (nestedness and modularity), but crops contained less specialized networks compared to forests and fragments and the species role in these habitats were changed. The networks in the rural coffee landscape maintain their structure in the different transformation scenarios, indicating that seed dispersal services are maintained even in the most transformed scenarios. Although the number of species does not decrease due to transformations, species change their roles in the most transformed habitats. This result sheds light on the way that bat-fruit networks respond to anthropogenic transformations, showing higher stability than theoretically predicted.

Seasonally dry tropical forests of the Gulf of Mexico: A degraded landscape undergoing homogenization or a promising, resilient reservoir?

Abstract: Seasonally dry tropical forests are amongst the most threatened ecosystems in the world due to severe and long-lasting anthropic disturbances. In this study, the spatial variation in plant diversity for the seasonally dry tropical region in central Veracruz was assessed at three different scales: among forested vegetation types, within each vegetation type and within forested patches. This region is characterized by extensive deforestation and today only 12% of its original forest cover remains. Of this, more than a third is early secondary forest. Woody vegetation was sampled in 29 forested patches (three 20 × 50 m transects per patch: 8.7 ha in total) belonging to six vegetation types. A total of 157 species were recorded (sample coverage >97%). Richness per patch was 3–33 spp., and 9 to 88 spp. per vegetation type. Species composition varied greatly across the region as indicated by the low values of compositional similarity (

Height-diameter allometric relationships for seedlings and trees across China

Abstract: Height–diameter allometric (H-D) relationships play an important role in the light capture and stability of a tree, and it is poorly understood whether the relationships changes with growth stages or functional groups along a large scale environmental gradients. We present a comparative study of H-D relationships of 6810 seedlings and 19,707 trees from about 1000 species in 9 different sites across China. We showed that allometric exponents for seedlings and trees differ between different sites and do not represent a single, constant theoretical value (e.g. 2/3, 1/2 or 1). Seedlings had greater exponents than trees in most sites. The exponents varied between canopy and understory trees in 5 sites, while were indistinguishable from each other in the remaining 4 sites. Canopy-tree seedlings had smaller exponents than understory-tree seedlings in 3 sites but had indistinguishable exponents in the other 6 sites. Gymnosperm trees had exponents greater than or indistinguishable from angiosperm trees. Elevation alone, or together with mean temperature of the warmest month explained variation of tree allometries for canopy-tree and understory-tree seedlings. The exponents of canopy trees decreased with mean annual precipitation. Our results do not support the predictions from metabolic scaling theory or biomechanical models that height–diameter allometries are invariant. Our study provides insight into how ontogeny, adult stature, phyletic affiliations and environmental limitations affect height–diameter allometric relationships at biogeographical scales.

Ecological similarity explains species abundance distribution of small mammal communities

Abstract: For several decades, ecologists have been trying to explain how species abundance distributions (SAD) emerge within communities. Niche models predict that species habitat requirements and life-history traits determine SADs. Here, based on predictions from a well-known niche-based SAD (Sugihara's model), we tested whether abundant species are ecologically less similar among each other than less abundant ones, and whether the strength of this relationship is reduced in high productivity areas. Using species abundance and trait data from 88 small mammal communities around the world we found that the most abundant species are similar to other abundant species, but less similar to rare species. However, this relationship is weakened in high-productivity areas, such as the tropics. These results suggest that niche differences moderate species abundances, and that low-productivity habitats have a reduced ecological space, especially for specialist species. A next step to uncover biological processes underlying the formation of SADs is to understand how they are influenced by the order of species arrivals during the assembly of communities.