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47 result(s) for "Guild ratio"
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Trait-Based Research on Rotifera: The Holy Grail or Just Messy?
In recent years, trait-based research on plankton has gained interest because of its potential to uncover general roles in ecology. While trait categories for phytoplankton and crustaceans have been posited, rotifer trait assessment has lagged behind. Here, we reviewed the literature to assess traits key to their life histories and provided a data matrix for the 138 valid genera of phylum Rotifera. We considered seven traits: habitat type, trophi type, presence of lorica and foot, predation defense attributes, corona type, and feeding traits. While most traits were morphological attributes and supposedly easy to assess, we were faced with several challenges regarding trait assignment. Feeding traits were especially difficult to assess for many genera because relevant information was missing. Our assembled trait matrix provides a foundation that will initiate additional research on rotifer functional diversity, diminish the misclassification of rotifer genera into trait categories, and facilitate studies across trophic levels.
Sessile rotifers (Rotifera) exhibit strong seasonality in a shallow, eutrophic Ramsar site in Mexico
To better understand the sessile rotifer community of a shallow, eutrophic lake, we monitored over a 1-year period the monthly changes in the density and diversity of rotifers on the roots of the common water hyacinth, Eichhornia crassipes, which served as a representative hydrophyte. Selected physical and chemical parameters of the water were also determined. Mean annual density of all sessile species was 630 individuals per ml. Species of Collothecacea (n = 7) were most abundant. Of the 12 species of Flosculariaceae (Flosculariidae), Sinantherina socialis occurred seasonally, while Ptygura beauchampi was most common across all seasons. The Shannon–Wiener diversity index was highest (H' = 2.8) in April, but decreased in January (H' = 1.3). Applying the concept of the guild ratio (functional-based analysis) we found that raptorial species (Collothecacea) were dominant over most of the year (June–February), while microphagous Flosculariidae were dominant during the warm, drier season (March–May). BEST (optimal matching of biota to environment, including stepwise search) analysis and canonical correspondence revealed that temperature, dissolved oxygen, pH, turbidity, and transparency strongly influenced sessile rotifer dynamics. We also found significant correlations between the density of some species and physicochemical variables. These species included Collotheca ambigua, C. coronetta, C. ornata, C. campanulata, C. tenuilobata, and Stephanoceros millsii in the Collothecacea; and Beauchampia crucigere, Limnias melicerta, L. ceratophylli, Ptygura crystallina, P. melicerta, and Sinantherina ariprepes in the Flosculariidae. Our study shows that the communities of sessile rotifers were structured by abiotic factors and that the guild ratio is useful for understanding the relationship between sessile rotifers and their substrata.
The structure of psammic rotifer communities in two boreal lakes with different trophic conditions: Lake Võrtsjärv and Lake Saadjärv (Estonia)
Psammon communities are still poorly studied worldwide. The aim of the present study was to establish the structure of psammic rotifer communities including their diversity and quantitative parameters. A total of 41 rotifer taxa were found in hydro-, hygro-, and euarenal zones of eutrophic Lake Võrtsjärv and mesotrophic Lake Saadjärv during the study carried out in Estonia in 2008, including 11 rotifer species new to Estonia. In L. Võrtsjärv, the predominant rotifer taxa were Bdelloidea and Lecane psammophila. L. psammophila dominated in July and August and bdelloids prevailed in the rest of the year. In L. Saadjärv, the most abundant taxa were Lepadella ovalis, Keratella hiemalis , and Cephalodella megalocephala . The psammic rotifer community of L. Saadjärv proved to be more diverse than that of L. Võrtsjärv. Microphagous rotifers were dominant in L. Võrtsjärv. Raptorial feeders dominated in L. Saadjärv in summer and autumn and were more abundant at sites with coarser sand and low plant density.
Culture, Marketization, and Owner-Manager Agency Costs: A Case of Merchant Guild Culture in China
This study explores cultural influence on corporate behavior employing the case of merchant guild culture in China and further the moderating role of Marketization. Using hand-collected data on merchant guild culture, we find that merchant guild culture is significantly negatively associated with owner-manager agency costs, suggesting that merchant guild culture in ancient China still has its continuous and remarkable effects on managerial behavior in contemporary corporations. This finding also implies that merchant guild culture motivates managers to upgrade the efficiency of controlling operating costs, reduces agency conflicts between management and shareholders, and eventually mitigates owner-manager agency costs. Moreover, provincial Marketization level attenuates the negative association between merchant guild culture and owner-manager agency costs. Above results are robust to a variety of alternative measures of merchant guild culture and owner-manager agency costs. Furthermore, our findings are still valid after controlling for the potential endogeneity between merchant guild culture and owner-manager agency costs.
Effect of long-term destocking on soil fungal functional groups and interactions with plants
Aims While the effects of destocking on soil nutrient and plant productivity are known, the effect on functional groups of fungi has received less attention. The objective of this study was to evaluate the effect of long-term destocking on fungal functional guilds and their association with plants and soil. Methods We characterized the changes in five fungal functional guilds, including plant pathogens, animal pathogens, wood saprotrophs, dung saprotrophs, and arbuscular mycorrhizal fungi (AMF), along a 35-year chronosequence following destocking at 0–60 cm soil depths on the Chinese Loess Plateau. Fungal community composition was assigned by comparing with the FUNGuild database. Results After 35 years of destocking, diversities of plant pathogens, wood saprotrophs, and AMF increased, while that of animal pathogens and dung saprotrophs decreased. Destocking had a greater effect in the near-surface layers (0–10 and 10–20 cm) owing to the greater influence of plant biomass and soil nutrients. Among the above- and belowground drivers, plant pathogen diversity was largely associated with plant diversity, while animal pathogens, dung saprotrophs, and wood saprotrophs were associated with aboveground biomass, AMF were responsive to soil conditions (e.g., organic C, NO 3 − -N, C:N ratio, and moisture). Conclusions Long-term destocking can be considered to be an important predictor of fungal functional guilds, and changes in these microorganisms were associated with cessation-induced shifts in plants and soil by grazing. Our findings provide insights into the duration of destocking necessary to benefit fungal communities, and how this varies according to soil depth.
To each its own: differential response of specialist and generalist herbivores to plant defence in willows
1. Plant-insect food webs tend to be dominated by interactions resulting from diffuse co-evolution between plants and multiple lineages of herbivores rather than by reciprocal co-evolution and co-cladogenesis. Plants therefore require defence strategies effective against a broad range of herbivore species. In one extreme, plants could develop a single universal defence effective against all herbivorous insects, or tailor-made strategies for each herbivore species. The evolution and ecology of plant defence has to be studied with entire insect assemblages, rather than small subsets of pairwise interactions. 2. The present study examines whether specialists and generalists in three coexisting insect lineages, forming the leaf-chewing guild, respond uniformly to plant phylogeny, secondary metabolites, nutrient content and mechanical antiherbivore defences of their hosts, thus permitting universal plant defence strategies against specialized and generalist folivorous insects from various taxa. 3. The extensive data on folivorous assemblages comprising three insect orders and 193 species are linked with plant phylogeny, secondary chemistry (salicylates, flavonoids and tannins), leaf morphological traits [specific leaf area (SLA) and trichome coverage], nutrient (C : N) content and growth form of eight willow (Salix) and one aspen (Populus) species growing in sympatry. 4. Generalists responded to overall host plant chemistry and trichomes, whilst specialists responded to host plant phylogeny and secondary metabolites that are unique to willows and that are capable of being utilized as an antipredator protection. We did not find any significant impact of other plant traits, that is SLA, C : N ratio, flavonoids, tannins and growth form, on the composition of leaf-chewing communities. 5. Our results show that the response to plant traits is differential among specialists and generalists. This finding constrains the ability of plants to develop defensive traits universally effective against herbivores and may lead to diversification of plant defensive mechanisms into several complementary syndromes, required for effective protection against generalists and specialists from multiple insect taxa comprising most leaf-chewing assemblages. These results point to the necessity of broad studies of plant–herbivore interactions, across multiple insect taxa and guilds.
Root trait-microbial relationships across tundra plant species
Fine roots, and their functional traits, influence associated rhizosphere microorganisms via root exudation and root litter quality. However, little information is known about their relationship with rhizosphere microbial taxa and functional guilds. We investigated the relationships of 11 fine root traits of 20 sub-arctic tundra meadow plant species and soil microbial community composition, using phospholipid fatty acids (PLFAs) and high-throughput sequencing. We primarily focused on the root economics spectrum , as it provides a useful framework to examine plant strategies by integrating the co-ordination of belowground root traits along a resource acquisition-conservation trade-off axis. We found that the chemical axis of the fine root economics spectrum was positively related to fungal to bacterial ratios, but negatively to Gram-positive to Gram-negative bacterial ratios. However, this spectrum was unrelated to the relative abundance of functional guilds of soil fungi. Nevertheless, the relative abundance of arbuscular mycorrhizal fungi was positively correlated to root carbon content, but negatively to the numbers of root forks per root length. Our results suggest that the fine root economics spectrum is important for predicting broader groups of soil microorganisms (i.e. fungi and bacteria), while individual root traits may be more important for predicting soil microbial taxa and functional guilds.
Moderately delayed maturation of composting promotes the reduction of guild-plant pathogenic fungi within vegetable waste
The relationships among the relative abundance of guild-plant pathogenic fungi, compost maturation index, and microbial community variation during vegetable waste composting, which are influenced by the C/N ratio, remain poorly understood. To address this, fungal communities were analyzed in composting treatments with C/N ratios of approximately 15 (CN15) and 25 (CN25), using vegetable waste as the primary raw material. The CN15 treatment showed greater microbial community variation and a better overall compost maturation index value than the CN25 treatment. However, the CN25 treatment had a greater decline in plant-pathogenic fungi than the CN15 treatment. Notably, the relative abundance of guild-plant pathogenic fungi was significantly negatively related to the compost maturity index in the CN25 treatment, while no significant relationship was observed in the CN15 treatment. This study suggests that the moderately delayed maturation of composting is beneficial for reducing guild-plant pathogenic fungi in vegetable waste.
Ecological and morphological traits predict depth-generalist fishes on coral reefs
Ecological communities that occupy similar habitats may exhibit functional convergence despite significant geographical distances and taxonomic dissimilarity. On coral reefs, steep gradients in key environmental variables (e.g. light and wave energy) restrict some species to shallow depths. We show that depth-generalist reef fishes are correlated with two species-level traits: caudal fin aspect ratio and diet. Fishes with high aspect ratio (lunate) caudal fins produce weaker vortices in the water column while swimming, and we propose that ‘silent swimming’ reduces the likelihood of detection and provides an advantage on deeper reefs with lower light irradiance and water motion. Significant differences in depth preference among trophic guilds reflect variations in the availability of different food sources along a depth gradient. The significance of these two traits across three geographically and taxonomically distinct assemblages suggests that deep-water habitats exert a strong environmental filter on coral reef-fish assemblages.
Leaf traits mediate changes in invertebrate herbivory along broad environmental gradients on Mt. Kilimanjaro, Tanzania
Temperature, primary productivity, plant functional traits, and herbivore abundances are considered key predictors of leaf herbivory but their direct and indirect contributions to community‐level herbivory are not well understood along broad climatic gradients. Here, we determined elevational herbivory patterns and used a path analytical approach to disentangle the direct and indirect effects of climate, land use, net primary productivity (NPP), herbivore abundance, and plant functional traits on community‐level invertebrate herbivory along the extensive elevational and land use gradients at Mt. Kilimanjaro, Tanzania. We recorded standing leaf herbivory caused by leaf chewers, leaf miners and leaf gallers on 55 study sites distributed in natural and anthropogenic habitats along a 3,060 m elevation gradient. We related the total community‐level herbivory to climate (temperature and precipitation), NPP, plant functional traits (specific leaf area, leaf carbon‐to‐nitrogen [CN] ratio and leaf nitrogen‐to‐phosphorus [NP] ratio) and herbivore abundances. Leaf herbivory ranged from 5% to 11% along the elevation gradient. Total leaf herbivory showed unimodal pattern in natural habitats but a strongly contrasting bimodal pattern in anthropogenic habitats. We also detected some variation in the patterns of leaf herbivory along environmental gradients across feeding guilds with leaf chewers being responsible for a disproportionally large part of herbivory. Path analyses indicated that the variation in leaf herbivory was mainly driven by changes in leaf CN and NP ratios which were closely linked to changes in NPP in natural habitats. Similarly, patterns of leaf herbivory in anthropogenic habitats were best explained by variation in leaf CN ratios and a negative effect of land use. Our study elucidates the strong role of leaf nutrient stoichiometry and its linkages to climate and NPP for explaining the variation in leaf herbivory along broad climatic gradients. Furthermore, the study suggests that climatic changes and nutrient inputs in the course of land use change may alter leaf herbivory and consequently energy and nutrient fluxes in terrestrial habitats. The authors' findings advance the debate on the role of plant functional traits in predicting ecosystem functions by showing its relevance across broad climatic gradients and at the level of ecological communities.