Susana Beatriz Perelman

Replacing fish oil (FO) in feeds remains a challenge for aquaculture sustainability. While experimental studies have evaluated the effects of alternative lipids on fillet long‐chain polyunsaturated fatty acids (LC‐PUFA) in rainbow trout, a quantitative synthesis of these effects is lacking. Here, 119 experimental diets from 29 controlled studies were synthesized through a statistical framework combining linear mixed‐effects models (LMM), generalized additive models (GAM), and leave‐one‐study‐out validation. Dietary docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) consistently predicted fillet DHA and EPA concentrations, independent of growth rate and not significantly influenced by temperature or lipid level. While growth performance was unaffected by FO replacement, LC‐PUFA deposition was not equivalent across lipid origins: FO and vegetable‐based diets supported steeper diet‐to‐fillet transfer slopes compared to animal‐derived lipids. GAMs revealed non‐linear thresholds, with active deposition occurring only when dietary LC‐PUFA exceeded near 10 mg g ⁻¹ and the dietary n‐6:n‐3 ratio remained below approximately 4. Temperature, modelled linearly, showed no significant effect on fillet LC‐PUFA deposition within the analysed dataset. These results demonstrate that FO can be reduced without compromising growth, but not without reformulating LC‐PUFA supply and precursor balance. Successful FO replacement is therefore a formulation problem rather than an ingredient substitution issue. Emerging sources such as algal oils or engineered oilseeds represent a viable pathway toward sustainable feeds delivering nutritionally valuable fillets. The identified dietary thresholds provide practical guidance for feed formulation by defining minimum LC‐PUFA inclusion levels and n‐6:n‐3 ratios required to achieve target fillet EPA and DHA concentrations under controlled temperature conditions.

Functional group composition can positively influence plant community invasibility through niche vacancy when the resident community does not sufficiently overlap with the invaders. Phenology plays a key role in determining functional group composition, as it defines the temporal scale on which niche overlap occurs. Defoliation may regulate the effect of functional group composition by releasing resources, resulting in interactive effects. In a manipulative experiment, we assembled native communities with different functional group compositions: perennial warm- and cool-season grasses growing either separately or together. These communities were subjected to two defoliation regimes to test the hypothesis that niche overlap determines the invasion success of Lolium multiflorum, an annual grass belonging to a functional group under-represented in the native flora of the region. We also hypothesized that higher defoliation intensity would increase community invasibility, promoting invasion and reducing the differences observed between communities under lower defoliation intensity. We evaluated this in two ontogenetic stages of the invader by counting seedlings and measuring above-ground biomass at the end of the growing season. The evidence shows that community invasibility is mediated by functional group composition through phenological overlap, although priority effects were also important. Defoliation intensity promoted seedling establishment similarly across all communities but did not affect the resulting above-ground biomass at the end of the growing season. Instead, it negatively impacted the performance of the invader growing in monoculture. Considering the variable effects on each ontogenetic stage is important for developing targeted management strategies at the appropriate temporal scale.

Genotype-phenotype associations between the bovine genome and grazing behaviours measured over time and across contexts have been reported in the past decade, with these suggesting the potential for genetic control over grazing personalities in beef cattle. From the large array of metrics used to describe grazing personality behaviours (GP-behaviours), it is still unclear which ones are linked to specific genes. Our prior observational study has reported associations and trends towards associations between genotypes of the glutamate metabotropic receptor 5 gene (GRM5) and four GP-behaviours, yet the unbalanced representation of GRM5 genotypes occurring in observational studies may have limited the ability to detect associations. Here, we applied a subsampling technique to create a genotypically-balanced dataset in a quasi-manipulative experiment with free ranging cows grazing in steep and rugged terrain of New Zealand’s South Island. Using quadratic discriminant analysis, two combinations of eleven GP-behaviours (and a total of fifteen behaviours) were selected to build an exploration model and an elevation model, respectively. Both models achieved ∼ 86% accuracy in correctly discriminating cows’ GRM5 genotypes with the training dataset, and the exploration model achieved 85% correct genotype prediction of cows from a testing dataset. Our study suggests a potential pleiotropic effect, with GRM5 controlling multiple grazing behaviours, and with implications for the grazing of steep and rugged grasslands. The study highlights the importance of grazing behavioural genetics in cattle and the potential use of GRM5 markers to select individuals with desired grazing personalities and built herds that collectively utilize steep and rugged rangelands sustainably.

Interesting botanical and ecological studies used the multivariate approach to describe underlying patterns in large data sets and to answer questions about the structure of the studied systems at various scales. This work aims to encourage the correct use of the multivariate approach and offers guidelines for the appropriate choice of the analysis techniques according to the objectives of the study and the characteristics of the data. Some appropriate applications of principal components, multidimensional scaling, correspondence analysis, discriminant, and cluster analysis in articles published in scientific journals of these disciplines are showed. We used reduced versions of the data matrices from some of these papers to present the methods of analysis in a simple way. The focus is placed on the correct interpretation of the results and the biological questions that can be answered through multivariate analysis.

Aims: To identify environmental and anthropogenic drivers of alpha‐ and beta‐diversity for native and alien plant species.Location: Río de la Plata grasslands, South America (Argentina, Brazil and Uruguay; 27.3–39.1°S, 50.1–66.5°W).Methods: We assembled a data set of 597 vegetation plots distributed across the Río de la Plata grasslands. To assess the drivers of native and alien alpha‐diversity (species richness), we performed a generalized least‐squares regression using environmental and anthropogenic predictors. We evaluated differences in beta‐diversity using Simpson's pairwise dissimilarity between pairs of plots and used multiple regression on distance matrixes to investigate environmental and anthropogenic drivers on compositional dissimilarity for both native and alien plant species.Results: Native species richness was higher in sites with less demanding environmental conditions, such as lower precipitation seasonality and soils with higher cation exchange capacity. Numbers of alien species were positively related to soil pH, cropland density and road density and negatively to precipitation seasonality, mean temperatures and soil cation exchange capacity. The compositional dissimilarity was similar for native and alien species assemblages (mean ± SD: 0.64 ± 0.16 and 0.64 ± 0.35 respectively). Areas having similar climates and being geographically close shared more taxonomically similar assemblages, for both native and alien assemblages, while soil had disparate effects. Compositional dissimilarity of alien plants decreased with increasing road density.Conclusions: Our results highlight a grassland ecosystem where native species richness is still shaped only by environmental factors, but both sets of factors influence its composition. On the other hand, alien plants carry a strong signal of both environmental and human factors. As time progresses the number of alien species tend to increase, eroding the patterns of native biodiversity. To avoid this, efforts should be made to reduce road encroachment and the conversion of natural grasslands into croplands.

Questions: Do remaining mesophytic grasslands on soils with agricultural potential respond to a latitudinal gradient? Are climatic or land‐use factors the principal drivers of regional and local diversity of these grasslands?Location: Mesophytic grasslands, Argentine Pampas, Rio de la Plata grasslands.Methods: The species presence and cover was recorded in each of 96 remnant grasslands on soils suitable for cropping, grouped into five sampling locations. In each region, CIs for γ‐diversity and for the slope of species/area curves were estimated. Unconstrained ordination was applied to detect the principal gradients in floristic composition and correlation analysis to identify their main drivers. Mantel test was used to evaluate the correlation between floristic similarity and geographic distance, and with Euclidean distance in fragmentation and climatic variables. To rank the climatic and land‐use factors that account for local species richness and percentge of exotics, we applied correlation analysis and regression models.Results: Community composition (73% native species) was mainly related to climatic variables determined by latitude, with a slight influence of fragmentation variables. Regional species richness responded to latitude: γ‐diversity decreased linearly with increasing distance from the Equator, as did the rate of species accumulation with expanding area. Alpha‐diversity did not vary in a systematic way with latitude, being associated with landscape fragmentation and mean annual precipitation. Relative importance of C₄ grasses and mean percentage exotics showed opposite latitudinal tendencies, the former decreasing and the latter increasing towards the south.Conclusions: Latitude was a strong determinant of regional diversity and community composition, but a partial driver for local species richness, mainly influenced by landscape fragmentation. While climatic and geographic drivers determined gradual latitudinal turnover in regional species pools, within regions land‐use history, stochastic processes and biotic interactions were also important. All these patterns need to be considered together when delimiting grassland nature reserves for conservation of the most diverse ecosystems of this region, currently threatened by agricultural expansion and intensification.

Questions: Are there losses in species richness due to extinctions? Is the input of new species lower in environments with strong resource limitation? Is there a decrease in abundance and diversity of native species due to anthropogenic disturbance at local and regional scale? Has abundance of exotic species been favoured by grazing increased? Are floristic changes associated with homogenization processes?Location: Two grassland community types of the Argentine Flooding Pampas: the mesophyte prairie and the halophyte steppe.Methods: Grassland sites (n = 51) were resurveyed with the same methodology after 35 yr. At the local scale (0.25 ha), we analysed alpha diversity, site colonization and extinction rates, and changes in species and functional type composition. Site colonization rates were calculated separately for new species (not recorded in the original inventory) and old species (present in the first survey at other sample sites of the community). Correspondence analysis was applied to the presence/absence species matrix for all sites in both periods. At regional scale, we evaluated gamma diversity, heterogeneity within and between communities, changes in proportion of functional types (growth season, longevity and life form) and species origin.Results: In the mesophytic prairie, average local species richness increased 46% and regional richness 28%, while in the halophytic steppe changes were not significant. The colonization rate was higher and the extinction rate lower in the richest community (mesophytic prairie). Differences in colonization rates between natives and exotics were not found. Principal variability between sites in species composition was associated with abiotic conditions explaining 20.9% of inertia, temporal changes were relegated to the second axis with 6.38%. Proportions of warm‐season exotics among new arrivals were higher than expected. Biotic homogenization was evidenced in the mesophytic prairie as a significant reduction in species turnover between sampling dates.Conclusions: After 35 yr under moderate grazing intensity we found increases in species richness, no biodiversity loss and no losses of native species. Instead of those species favoured by grazing, as expected, warm season species increased. Different grassland communities showed clear differences in richness changes, in degree of homogenization and in species turnover.

Questions: Plant communities fulfil key functions in the ecosystem, which can be characterized by their plant functional traits. In functional ecology, plant communities are considered to hold a set of trait attributes reflecting a specific plant strategy adapted to persist in the environment to which they are exposed. In semi‐arid grasslands of the Republic of South Africa, we addressed the following questions: how are community‐aggregated plant functional traits (CPFT) shaped by grazing gradients; which plant strategies are associated with the response of CPFTs; and are environmental factors, such as soil properties and grazing management, interrelated with the functional response of vegetation to grazing gradients?Location: Semi‐arid grasslands close to Thaba Nchu, Free State (Republic of South Africa).Methods: Piosphere transects from a water point into the field were established to portray grazing gradients on two communal grazing areas with continuous grazing and two commercial farms with rotational grazing. Along each transect, six plots (5 × 5 m) were evenly distributed. The trait–transect sampling was applied to record 12 CPFT related to light capture and forage quality. A redundancy analysis was performed to derive relationship between CPFTs, grazing gradients and environmental conditions.Results: Grazing intensity decreased along piosphere transects, from the water point into the field. Most CPFTs responded to this decreasing gradient of grazing intensity and so allowed derivation of trait syndromes that clearly reflect plant strategies of ruderal and competitive vegetation. Close to water points, plants had higher nitrogen concentrations, fewer cell wall components and higher specific leaf area, hence light capture might be faster and more efficient per leaf area and leaf mass. Plant communities exposed to intensive grazing were well adapted to defoliation, trampling and nutrient accumulation through fast growth rates and a quick return strategy.Conclusions: In the sacrifice zone around water points, there is an ecological niche for vegetation communities exhibiting a strategy of fast growth, which is well adapted to intense and frequent grazing and is also associated with forage of high nutritional quality.