Seasonal resource use and niche breadth in an assemblage of coexisting grazers in a fenced Park

Many small Parks inKenyaare being fenced to control human-wildlife conflict. Some of these Parks have a diversity of large herbivores which might increase in density in the wake of fencing and subsequent compression of their home ranges due to closure of their migratory routes. It is important to understand the consequences of such an increase on the structuring of insularised herbivore assemblages in such Parks. We studied seasonal resource segregation and niche breadth variation as mechanisms of coexistence in a high density grazer assemblage inLakeNakuruNational Parkwhich is small and completely fenced. Diet composition and habitat use were considered as variables of resource use. We predicted that overlap in resource use and niche breadth would be the smallest among grazers with similar body weights in the dry season which is the most resource limiting for grazers in East Africa. Our results were contrary to the predictions because of lack of seasonal differentiation in the overlap of diet composition and habitat use, and in niche breadth. Overlaps in resource use were consistently high during both the wet and dry seasons, and niche breadth contraction during the dry season was not possible probably because of lack of species-specific niches during the dry season. Our results suggest that there might be competitive interactions in this grazer assemblage which is an important parameter to consider in the management of the Park.

Niche breadth and overlap of spotted deer and domestic cattle with swamp deer in tropical region of Nepal

Background:Knowledge about the niche overlap among wild species and domestic cattle is helpful to conserve and manage wildlife.We assessed the habitat niche breadth and overlap of sympatrically living spotted deer(Axis axis)and domestic cattle with swamp deer(Cervus duvaucelii)in Shuklaphanta National Park,Nepal during the dry season to explore the possibility of interspecific competition by studying the habitat use by these species.The assumption was made that the presence of pellets is proof of habitat used by species.Methods:Grids of 2 km×2 km have four subgrids,each with four sample plots,making a total of 16 plots(20 m×20 m)in each grid.The size of each sub-grid was 200 m×200 m and they were placed randomly inside the grid but at least 1 km apart from one another.The data was collected in a 96 plots in total.Levin’s niche breadth and Morisita’s overlap index were calculated to determine the niche breadth and the habitat overlap,respectively.Results:The Levin’s measure of niche breadth suggested that spotted deer had the highest acclimatization with an index value of 0.94,followed by domestic cattle at 0.50,and swamp deer at 0.33 in our study area.Thus,our findings supported the evidence that spotted deer are habitat generalists,whereas swamp deer are habitat specialists.The swamp deer had lower niche breadth and more overlap with domestic cattle.Conclusion:Our study showed the least niche breadth of swamp deer in comparison to spotted deer and domestic cattle.The domestic cattle had the highest and least niche overlap with spotted deer and swamp deer,respectively,in terms of habitat use.Our study suggests that domestic cattle grazing should be stopped,and grassland management should be carried out for the benefit of ungulates.Similar studies should be conducted,including different seasons and places,prior to appropriate habitat management.In addition,further studies are needed to quantify the extent of interspecific competition by incorporating more species.

Multiple Spatial Scale Analysis of the Niche Characteristics of the Rhododendron dauricum Plant Communities in Northeast China

This study aims to verify the concept of niches at multiple spatial scales in plant communities.To this end,we analyzed the niche characteristic of Rhododendron dauricum plant communities in Northeast China at three spatial scales.At the local scale,we calculated the Importance Value(IV)of species in five communities in the north of the Da Hinggan Mountains.At the intermediate scale,we examined five communities in their entirety,calculated the niche breadth of the species,and integrated niche overlap and interspecific association to analyze interspecific relationships.Further,the generalized additive model(GAM)was used to analyze the impact of topography and soil factors on niche characteristics.At the regional scale,we analyzed the geographical distribution of dominant species of R.dauricum plant communities in Northeast China and used principal component analysis(PCA)to analyze the impact of geographical and climate factors on species distribution.The results show that at the local scale,the IV of the species in each community varies widely.At the intermediate scale,species with a wide niche breadth tend to have a high value for IV.Larix gmelinii,Betula platyphylla,R.dauricum,Ledum palustre,and Vaccinium vitis-idaea had a relatively wide niche breadth and a high niche overlap,and the interspecific associations were almost all positive.Elevation and soil nutrients were the most dominant environmental factors.At the regional scale,species with a wide niche breadth tend to have a wide range of distribution,and temperature and precipitation were the most dominant environmental factors.This study suggests that the niche characteristics at three scales are both related and different.Niche characteristics at the local scale were various and labile,and niche characteristics at the intermediate and regional scales were relatively regular.These results show some degree of consistency with previous studies from an evolutionary perspective.The action mechanisms of these communities are related to differences in the dominant environmental factors.In addition,the integration of niche overlap and interspecific association determine interspecific relationships more accurately.

Feeding ecology of Japanese Spanish mackerel(Scomberomorus niphonius)along the eastern coastal waters of China

Feeding activities provide necessary nutrition and energy to support the reproduction and development of fish populations.The feeding ecology and dietary plasticity of fish are important factors determining their recruitment and population dynamics.As a top predator,Japanese Spanish mackerel(Scomberomorus niphonius)supports one of the most valuable fisheries in China.In this study,the feeding ecology and diet composition of Japanese Spanish mackerel spawning groups were analysed based on samples collected from six spawning grounds along the eastern coastal waters of China during spring(March to May)in 2016 and 2017.Both stomach contents and stable isotope analysis were conducted.Stomach content analysis showed that spawning groups of Japanese Spanish mackerel mainly fed on fish,consuming more than 40 different prey species.Diets were significantly different among sampling locations.The most important prey species were Stolephorus in Fuzhou,Japanese anchovy Engraulis japonicus in Xiangshan,Euphausia pacifica in Lüsi,sand lance Ammodytes personatus in Qingdao and Weihai,and Leptochela gracilis in Laizhou Bay.Stable isotope analysis showed that the trophic level of Japanese Spanish mackerel was relatively high and generally increased with latitude from south to north.In the 1980 s,the diet of Japanese Spanish mackerel was dominated solely by Japanese anchovies in the eastern coastal waters of China.The results in the present study showed that the importance of Japanese anchovies declined considerably,and this fish was not the most dominant diet in most of the investigated waters.Both the spatial variations in diet composition and changes in the dominant diet over the long term indicated the high adaptability of Japanese Spanish mackerel to the environment.Combining the results of stomach analysis and stable isotope analysis from different tissues provided more comprehensive and accurate dietary information on Japanese Spanish mackerel.The study provides essential information about the feeding ecology of Japanese Spanish mackerel and will benefit the management of its populations in the future.

Inter-individual variation in provisioning rate,prey size and number,and links to total prey biomass delivered to nestlings in the Collared Flycatcher(Ficedula albicollis)

Background:In bird species where offspring growth and survival rely on parents’food provisioning,parents can maximise their fitness by increasing the quantity and/or the quality of preys delivered to their offspring.Many studies have focused on inter-individual variation in feeding rate,yet this measure may not accurately reflect the total amount of food(i.e.energy)provided by parents if there is large variation in the quantity and quality of preys at each feeding.Here,we explored the relative role of individual(sex,age,body condition),breeding(hatching date,brood size)and environmental(temperature)factors on feeding rate,prey number,size and quality,and their contribution to total prey biomass delivered to the nestlings of 164 Collared Flycatcher(Ficedula albicollis)parents in 98 nests.Results:Preys delivered to the nest were mainly larvae(53.6%)and flying insects(45.6%).Feeding rate increased with brood size and age,and was higher in males than females.Mean prey number decreased,but mean prey size increased,as the season progressed and parents feeding their brood with primary larvae brought more preys per visit.Relationships between feeding rate,mean prey number and size remained when taking into account the provision-ing quality:parents brought either a large number of small prey or a small number of larger items,and the force of the trade-offs between feeding rate and mean prey number and size depended on the quality of the provisioning of the parents.Whatever the percentage of larvae among preys in the provisioning,the variance in total prey biomass was foremost explained by feeding rate(65.1%to 76.6%)compared to mean prey number(16.4%to 26%)and prey size(2.7%to 4%).Conclusions:Our study shows that variation in feeding rate,prey number,size,but not quality(i.e.percentage of lar-vae),were influenced by individual factors(sex and age)and breeding decisions(brood size and timing of breeding)and that,whatever the provisioning strategy adopted,feeding rate was the best proxy of the total biomass delivered to the nestlings.

Towards a trait-based quantification of species niche

Aims Although the niche concept is of prime importance in ecology,the quantification of plant species’niches remains difficult.Here we propose that plant functional traits,as determinants of species performance,may be useful tools for quantifying species niche parameters over environmental gradients.Important findings Under this framework,the mean trait values of a species determine its niche position along gradients,and intraspecific trait variability determines its niche breadth.This trait-based approach can provide an operational assessment of niche for a potentially large number of species,making it possible to understand and predict species niche shifts under environmental changes.We further advocate a promising method that recently appeared in the literature,which partitions trait diversity into among-and within-community components as a way to quantify the species niche in units of traits instead of environmental parameters.This approach allows the switch of the focus from ecological niches to trait niches,facilitating the examination of species coexistence along undefined environmental gradients.Altogether,the trait-based approach provides a promising toolkit for quantifying the species ecological niche and for understanding the evolution of species niche and traits.

Biodegradable dissolved organic carbon shapes bacterial community structures and co-occurrence patterns in large eutrophic Lake Taihu

Interactions between dissolved organic matter(DOM)and bacteria are central in the biogeochemical cycles of aquatic ecosystems;however,the relative importance of biodegradable dissolved organic carbon(BDOC)compared with other environmental variables in structuring the bacterial communities needs further investigation.Here,we investigated bacterial communities,chromophoric DOM(CDOM)characteristics and physico-chemical parameters as well as examined BDOC via bioassay incubations in large eutrophic Lake Taihu,China,to explore the importance of BDOC for shaping bacterial community structures and co-occurrence patterns.We found that the proportion of BDOC(%BDOC)correlated significantly and positively with the DOC concentration and the index of the contribution of recent produced autochthonous CDOM(BIX).%BDOC,further correlated positively with the relative abundance of the tryptophan-like component and negatively with CDOM aromaticity,indicating that autochthonous production of protein-like CDOM was an important source of BDOC.The richness of the bacterial communities correlated negatively with%BDOC,indicating an enhanced number of species in the refractory DOC environments.%BDOC was identified as a significant stronger factor than DOC in shaping bacterial community composition and the co-occurrence network,suggesting that substrate biodegradability is more significant than DOC quantity determining the bacterial communities in a eutrophic lake.Environmental factors explained a larger proportion of the variation in the conditionally rare and abundant subcommunity than for the abundant and the rare bacterial subcommunities.Our findings emphasize the importance of considering bacteria with different abundance patterns and DOC biodegradability when studying the interactions between DOM and bacteria in eutrophic lakes.