Interspecific Effects Research Articles

Multi-Environment Genome-Wide Association Studies of Yield Traits in Common Bean (Phaseolus vulgaris L.) × Tepary Bean (P. acutifolius A. Gray) Interspecific Advanced Lines in Humid and Dry Colombian Caribbean Subregions

Assessing interspecific adaptive genetic variation across environmental gradients offers insight into the scale of habitat-dependent heritable heterotic effects, which may ultimately enable pre-breeding for abiotic stress tolerance and novel climates. However, environmentally dependent allelic effects are often bypassed by intra-specific single-locality genome-wide associations studies (GWAS). Therefore, in order to bridge this gap, this study aimed at coupling an advanced panel of drought/heat susceptible common bean (Phaseolus vulgaris L.) × tolerant tepary bean (P. acutifolius A. Gray) interspecific lines with last-generation multi-environment GWAS algorithms to identify novel sources of heat and drought tolerance to the humid and dry subregions of the Caribbean coast of Colombia, where the common bean typically exhibits maladaptation to extreme weather. A total of 87 advanced lines with interspecific ancestries were genotyped by sequencing (GBS), leading to the discovery of 15,645 single-nucleotide polymorphism (SNP) markers. Five yield traits were recorded for each genotype and inputted in modern GWAS algorithms (i.e., FarmCPU and BLINK) to identify the putative associated loci across four localities in coastal Colombia. Best-fit models revealed 47 significant quantitative trait nucleotides (QTNs) distributed in all 11 common bean chromosomes. A total of 90 flanking candidate genes were identified using 1-kb genomic windows centered in each associated SNP marker. Pathway-enriched analyses were done using the mapped output of the GWAS for each yield trait. Some genes were directly linked to the drought tolerance response; morphological, physiological, and metabolic regulation; signal transduction; and fatty acid and phospholipid metabolism. We conclude that habitat-dependent interspecific polygenic effects are likely sufficient to boost common bean adaptation to the severe climate in coastal Colombia via introgression breeding. Environmental-dependent polygenic adaptation may be due to contrasting levels of selection and the deleterious load across localities. This work offers putative associated loci for marker-assisted and genomic selection targeting the common bean’s neo-tropical lowland adaptation to drought and heat.

Spatial co-occurrence patterns of sympatric large carnivores in a multi-use African system.

Interspecific interactions can be a key driver of habitat use, and must be accounted for in conservation planning. However, spatial partitioning between African carnivores, and how this varies with scale, remains poorly understood. Furthermore, most studies have taken place within small or highly protected areas, rather than in the heterogeneous, mixed-use landscapes characteristic of much of modern Africa. Here, we provide one of the first empirical investigations into population-level competitive interactions among an African large carnivore guild. We collected detection/non-detection data for an eastern African large carnivore guild in Tanzania's Ruaha-Rungwa conservation landscape, over an area of ~45,000 km2. We then applied conditional co-occupancy models to investigate co-occurrence between lion, leopard, and African wild dog, at two biologically meaningful scales. Co-occurrence patterns of cheetah and spotted hyaena could not be modelled. After accounting for habitat and detection effects, we found some evidence of wild dog avoidance of lion at the home range scale, and strong evidence of fine-scale avoidance. We found no evidence of interspecific exclusion of leopard by lion; rather, positive associations were observed at both scales, suggesting shared habitat preferences. We found little evidence of leopard habitat use being affected by wild dog. Our findings also reveal some interspecific effects on species detection, at both scales. In most cases, habitat use was driven more strongly by other habitat effects, such as biotic resources or anthropogenic pressures, than by interspecific pressures, even where evidence of the latter was present. Overall, our results help shed light on interspecific effects within an assemblage that has rarely been examined at this scale. We also demonstrate the effectiveness of sign-based co-occurrence modelling to describe interspecific spatial patterns of sympatric large carnivores across large scales. We conclude by discussing the implications of our findings for large carnivore conservation in modern African systems.

Phosphorus availability mediates plant–plant interaction and field productivity in maize-grass pea intercropping system: Field experiment and its global validation

CONTEXTPlant–plant competitive and facilitative interactions might strongly affect the biodiversity effect and field productivity of intercropping system under the condition of limited resources such as available phosphorus (P). To test this hypothesis, the maize–grass pea intercropping system with five P application gradients (from low- to high-P) was experimentally investigated and the global meta-analysis validation was simultaneously performed. OBJECTIVEThe main objectives of this study included as: 1) to examine the characteristics of plant–plant interaction variations along soil P addition gradients; 2) to identify the shift from interspecific complementarity to selection effect regarding the productivity and nutrient uptake and its driving mechanism; 3) to verify the universality of above phenomenon via global meta-analysis and explore the general pattern of P-dependent plant–plant interactions in the intercropping systems. RESULTS AND CONCLUSIONSRegardless of growing seasons, the total net effect of intercropping system was always >0, showing net facilitative effects of plant–plant interactions on field productivity and nutrient uptake efficiency, relative to monoculture systems. On average, the yield, biomass, N and P uptake were elevated by 3.0–13.7%, 3.2–12.8%, 7.5–20.1% and 5.6–18.9% in intercropping respectively, relative to those of monoculture. On the other hand, the contribution of complementarity effect to the total net effect was up to 78.7%, much more than that of selection effect (21.3%). The relative interaction index tended to decline remarkably with increasing soil P availability (from 0.097–0.126 to 0.027–0.029), suggesting that the facilitation (rather than the competition) dominated in intercropping under the low-P condition. Furthermore, the intercropped grass pea decreased the harvest index and allocated more biomass to vegetative growth as a result of the enhanced interspecific competition under the P-sufficient condition. Finally, the meta-analysis demonstrated that intercropping system had greater relative benefits regarding field productivity and N/P acquisition and utilization than monoculture system. In the meanwhile, the intensity of interspecific facilitative effect was enhanced under the P-deficient condition. SIGNIFICANCEField observations presented the evidences regarding the P-dependent plant-plant interactions and its effects on field productivity in the maize-grass pea intercropping system. The meta-analysis confirmed that high P application decreased the interspecific facilitative effects in terms of field productivity and nutrient utilization in the intercropping systems. But the low-P condition led to the opposite trend, i.e. facilitative effect dominated in the intercropping for greater productivity efficiency.

Bandwidth Row Ratio Configuration Affect Interspecific Effects and Land Productivity in Maize–Soybean Intercropping System

Intercropping plays an indispensable role in sustainable agriculture. The response of bandwidth row ratio configuration to crop interspecific relationships and land productivity in the maize–soybean intercropping system (MSI) is still unclear. A 2-year field experiment was conducted with sole maize (SM) and sole soybean (SS), two different bandwidths (2.4 m (B1), 2.8 m (B2)), two different maize and soybean row ratios (2:3 (R1), and 2:4 (R2)) for MSI. The results showed that intercropping had advantages for land productivity compared with sole planting. Intercropping cropping had significant differences on crop yield under different intercropping treatments. The 2-yr average land equivalent ratio (LER, 1.59) and group yield under the intercropping patterns of B1R2 were significantly higher than other intercropping treatments (p < 0.05). With a bandwidth of 2.4 m and planting four rows of intercropped soybean, the total LER and group yield increased by 7.57% and 10.42%, respectively, compared to planting three rows of soybean. Intercropped maize was the dominant species and also had a higher nutrient aggressivity than intercropped soybean. The complementarity effect was higher than the select effect in the MSI system, and intercropping advantage was mainly derived from the complementarity effect, which was significantly correlated with intercropped maize yield. Nitrogen and phosphorus nutrient aggressivity in intercropped maize showed significant correlations with group yield and intercropped maize yield. In conclusion, bandwidth 2.4 m, row ratio 2:4 was a reasonable planting pattern because of its superior land productivity, crop nutrients uptake advantage, and harmonious interspecific relationship, which could provide a reference for MSI promotion and application research.

Synergistic removal of nitrate by a cellulose-degrading and denitrifying strain through iron loaded corn cobs filled biofilm reactor at low C/N ratio: Capability, enhancement and microbiome analysis

Optimization of nitrate removal rate under low carbon-to-nitrogen ratio has always been one of the research hotspots. Biofilm reactor based on functional carrier and using interspecific synergic effect of strains provides an insight. In this study, iron-loaded corn cob was used as a functional carrier that can contribute to the cellulose degradation, iron cycling, and collaborative denitrification process of microorganisms. During biofilm reactor operation, the maximum nitrate removal efficiency was 99.30% and could reach 81.73% at no carbon source. Dissolved organic carbon and carrier characterization showed that strain ZY7 promoted the release of carbon source. The crystallinity of cellulose I and II in carrier of experimental group increased by 31.26% and decreased by 21.83%, respectively, in comparison to the control group. Microbial community showed the synergistic effect among different strains. The vitality and metabolic activity of the target microorganisms in bioreactor were increased through interspecific bacterial cooperation.

The Evolution of Competitive Ability.

AbstractCompetition drives evolutionary change across taxa, but our understanding of how competitive differences among species directs the evolution of interspecific interactions remains incomplete. Verbal models assume that interspecific competition will select for reducing a species' sensitivity to competition with their opponent; however, they do not consider the potential for other demographic components of competitive ability to evolve, specifically, interspecific effects, intraspecific interactions, and intrinsic growth rates. To better understand how competitive ability evolves, we set out to explore how each component has evolved and whether their evolution has been constrained by trade-offs. By setting sympatric and allopatric populations of an annual grass in competition with a dominant invader, we demonstrate (1) that in response to interspecific competition, populations can evolve increased competitive ability through either reduced interspecific or, surprisingly, reduced intraspecific competition; (2) that trade-offs do not always constrain the evolution of competitive ability but rather that parameters may correlate in ways that mutually beget higher competitive ability; and (3) that the evolution of one species can influence the competitive ability of its opponent, a consequence of how competitive ability is defined ecologically. Overall, our results reveal the complexity with which demographic components evolve in response to interspecific competition and the impact past evolution can have on present-day interactions.

Linking quantitative genetics with community-level performance: Are there operational models for plant breeding?

Plant breeding is focused on the genotype and population levels while targeting effects at higher levels of biodiversity, from crop covers to agroecosystems. Making predictions across nested levels of biodiversity is therefore a major challenge for the development of intercropping practices. New prediction tools and concepts are required to design breeding strategies with desirable outcomes at the crop community level. We reviewed theoretical advances in the field of evolutionary ecology to identify potentially operational ways of predicting the effects of artificial selection on community-level performances. We identified three main types of approaches differing in the way they model interspecific indirect genetic effects (IIGEs) at the community level: (1) The community heritability approach estimates the variance for IIGE induced by a focal species at the community level; (2) the joint phenotype approach quantifies genetic constraints between direct genetic effects and IIGE for a set of interacting species; (3) the community-trait genetic gradient approach decomposes the IIGE for a focal species across a multivariate set of its functional traits. We discuss the potential operational capacities of these approaches and stress that each is a special case of a general multitrait and multispecies selection index. Choosing one therefore involves assumptions and goals regarding the breeding target and strategy. Obtaining reliable quantitative, community-level predictions at the genetic level is constrained by the size and complexity of the experimental designs usually required. Breeding strategies should instead be compared using theoretically informed qualitative predictions. The need to estimate genetic covariances between traits measured both within and among species (for IIGE) is another obstacle, as the two are not determined by the exact same biological processes. We suggest future research directions and strategies to overcome these limits. Our synthesis offers an integrative theoretical framework for breeders interested in the genetic improvement of crop communities but also for scientists interested in the genetic bases of plant community functioning.

Patterns of leaf trait variation underlie ecological differences among sympatric tree species of Damburneya in a tropical rainforest.

Although ecological differentiation driven by altitude and soil is hypothesized to promote coexistence of sympatric tree species of Damburneya (Lauraceae), the mechanistic role of leaf functional variation on ecological differentiation among co-occurring species remains unexplored. We aimed to determine whether the patterns of leaf trait variation reflect ecological differences among sympatric Damburneya species. We tested whether trait correlations underlying functional strategies and average species traits vary in response to local soil heterogeneity along an altitudinal gradient, potentially affecting species distributions. At two contrasting altitudes (100, 1100 m a.s.l.) in a Mexican tropical rainforest, we characterized soil chemical and physical properties and sampled four Damburneya species to quantify five leaf functional traits. We used linear models to analyze paired and multivariate trait correlations, spatial and interspecific effects on trait variation, and trait response to local soil heterogeneity. Relative contributions of intra- and interspecific variation to local trait variability were quantified with an ANOVA. Soil nutrient availability was higher at low altitude, but all species had a high leaf N:P ratio across altitudes suggesting a limited P supply for plants. Species distribution differed altitudinally, with some species constrained to low or high altitude, potentially reflecting soil nutrient availability. Leaf traits responded to altitude and local soil properties, suggesting interspecific differences in functional strategies according to the leaf economics spectrum (conservative vs. acquisitive). The interspecific divergence in functional strategies in response to local environmental conditions suggests that trait variation could underlie ecological differentiation among Damburneya sympatric species.

Community assembly along climatic gradient: Contrasting pattern between- and within- species

Grime’s CSR classification of functional strategies in terms of competitors, stress-tolerators and ruderals provides a helpful framework for understanding and predicting vegetation responses to environmental changes. To evaluate the importance of alternative processes that structure plant communities, it is useful to disentangle the community functional variation into interspecific and intraspecific components and assess their degree of co-variation. Few efforts have been made to investigate the habitat filtering theory in all the interspecific and intraspecific components of a plant community. We hypothesized that under intense climatic conditions, such as drought and cold, functional diversity would decrease towards the dominance of stress tolerant strategies, and that such trends would be reinforced by similar variation at the intraspecific level. We investigated the effect of climatic variation on functional diversity and on community-weighted mean along an elevation gradient in central Italy that ranges from dry and warm climatic conditions at lower elevation to cold and moist ones at higher elevation. We ran regression models to disentangle the total community components for both functional diversity and community-weighted mean into interspecific effect, intraspecific effect and their covariation along the climatic gradient. Our observations were in line with the theory of habitat filtering: we found lower diversity of the Grime strategy for species at both warmer and colder climatic conditions, with dominance of the stress-tolerant strategy. Similarly, the intraspecific effect was lower in cold conditions but higher under drier conditions, which seems to indicate that different processes act at the level of individuals. Given the important intraspecific variability observed in this study, it can be proposed that investigations of vegetation communities should take the role of intraspecific variability into greater consideration.

Comspat: an R package to analyze within‐community spatial organization using species combinations

The diversity of species combinations observable in sampling units reflects a species' uneven distribution and preference for specific abiotic and biotic conditions – a phenomenon most commonly expressed in terms of ecological assembly rules of plant communities and other sessile organisms (e.g. subtidal algae, invertebrates and coral reefs). We present comspat, a new R package that uses grid or transect data sets to measure the number of realized (observed) species combinations (NRC) and the Shannon diversity of realized species combinations (compositional diversity; CD) as a function of spatial scale. NRC and CD represent two measures from a model family developed by Pál Juhász‐Nagy based on information theory. Classical Shannon diversity measures biodiversity based on the number and relative abundance of species, whereas the specific version of Shannon diversity presented here characterizes biodiversity and provides information on species coexistence relationships; both measures operate at fine‐scale within the sampling unit or within the community. comspat offers two commonly applied null models, complete spatial randomness and random shift, to disentangle the textural, intraspecific and interspecific effects on the observed spatial patterns. Combined, these models assist users in detecting and interpreting spatial associations and inferring assembly mechanisms. Our open‐sourced package provides a vignette that describes the method and reproduces the figures from this paper to help users contextualize and apply functions to their data.

Interspecific competition among terrestrial slugs

ABSTRACT Interspecific competition among terrestrial gastropods has previously been considered to have little effect on population dynamics and local distribution. Recent studies, however, demonstrate several cases in which interspecific competition plays a major role in structuring terrestrial gastropod communities. To explore the general importance of interspecific competition for the ecology of slugs, we conducted a semi-systematic literature review, synthesizing available peer-reviewed literature relating interspecific interactions to the following: (1) mortality and reproduction; (2) activity, movement, feeding and growth; and (3) habitat use and geographical distribution of slugs. To support the literature on slugs, we also reviewed literature on terrestrial snails. The body of available literature is relatively limited, but the effect of interspecific competition on survival, reproduction, movement and activity has clearly been demonstrated in laboratory experiments for different slug species. The occurrence of interspecific competition seems, however, to be species specific, and no negative effects due to the presence of heterospecifics have been reported for many of the species combinations investigated to date. Most of the studies demonstrating interspecific effects between slug species involved interference from a few aggressive species (mainly Limax maximus as the aggressor). In addition, several correlative studies have indicated that in terrestrial gastropods, habitat use and geographical distribution might be mediated by interspecific competition. Further, well-designed experiments are needed to explore the general importance of interspecific competition among slugs, potentially with a focus on interactions between invasive and native species, where the lack of a shared evolutionary history and niche separation may increase the intensity of competition. Such experimental studies may produce information that has implications for the conservation of native species, as well as for management of invasive pests, because interspecific competition may result in local extinction of vulnerable species and influence the possibility of non-native species establishing invasive populations in new areas.

Mandible shape variation and feeding biomechanics in minks

European and American minks are very similar in ecology, behavior and morphology. Both species hunt terrestrial vertebrates and aquatic prey, but the American mink is a more generalist predator which, among other factors, allows it to outcompete the European mink in areas where it has been introduced. We used 3D geometric morphometrics and estimates of muscle mechanical advantage to assess the degree of variation in mandibular morphology, and to determine whether such variation reflects dietary differences between the two species. The three main axes of variation represented interspecific differences, a common allometric trajectory between species and sexes, and the interspecific effect of sexual size dimorphism, with males having overall stronger bites than females. Differences in mandible shape and biomechanical parameters suggest that American minks are better equipped for preying on terrestrial vertebrates, while the features seen in European mink could be related to tougher prey, fish capture, or both. Additionally, within each species, the larger specimens of each sex present indicators of a higher percentage of terrestrial prey in their diet. These results indicate a low potential dietary overlap between both species, suggesting that factors other than prey competition may have a role in the decline of the European mink.

Invader abundance and contraction of niche breadth during replacement of a native gammarid amphipod.

The introduction of non‐native species to new locations is a growing global phenomenon with major negative effects on native species and biodiversity. Such introductions potentially bring competitors into contact leading to partial or total species replacements. This creates an opportunity to study novel species interactions as they occur, with the potential to address the strength of inter‐ and intraspecific interactions, most notably competition. Such potential has often not been realized, however, due to the difficulties inherent in detecting rapid and spatially expansive species interactions under natural field conditions. The invasive amphipod crustacean Gammarus pulex has replaced a native species, Gammarus duebeni celticus, in river and lake systems across Europe. This replacement process is at least partially driven by differential parasitism, cannibalism, and intraguild predation, but the role of interspecific competition has yet to be resolved. Here, we examine how abundance of an invasive species may affect spatial niche breadth of a native congeneric species. We base our analyses of niche breadth on ordination and factor analysis of biological community and physical parameters, respectively, constituting a summative, multidimensional approach to niche breadth along environmental gradients. Results derived from biological and environmental niche criteria were consistent, although interspecific effects were stronger using the biological niche approach. We show that the niche breadth of the native species is constrained as abundance of the invader increases, but the converse effect does not occur. We conclude that the interaction between invasive G. pulex and native G. d. celticus under natural conditions is consistent with strong interspecific competition whereby a native, weaker competitor is replaced by a superior invasive competitor. This study indicates a strong role of interspecific competition, alongside other known interactions such as differential intraguild predation, in rapid and expansive species replacements following biological invasions.

Interacting phenotypes and the coevolutionary process: Interspecific indirect genetic effects alter coevolutionary dynamics.

Coevolution occurs when species interact to influence one another's fitness, resulting in reciprocal evolutionary change. In many coevolving lineages, trait expression in one species is modified by the genotypes and phenotypes of the other, forming feedback loops reminiscent of models of intraspecific social evolution. Here, we adapt the theory of within-species social evolution, characterized by indirect genetic effects and social selection imposed by interacting individuals, to the case of interspecific interactions. In a trait-based model, we derive general expressions for multivariate evolutionary change in two species and the expected between-species covariance in evolutionary change when selection varies across space. We show that reciprocal interspecific indirect genetic effects can dominate the coevolutionary process and drive patterns of correlated evolution beyond what is expected from direct selection alone. In extreme cases, interspecific indirect genetic effects can lead to coevolution when selection does not covary between species or even when one species lacks genetic variance. Moreover, our model indicates that interspecific indirect genetic effects may interact in complex ways with cross-species selection to determine the course of coevolution. Importantly, our model makes empirically testable predictions for how different forms of reciprocal interactions contribute to the coevolutionary process.

Monitoring post-fire neighborhood competition effects on pine saplings under different environmental conditions by means of UAV multispectral data and structure-from-motion photogrammetry

In burned landscapes, the recruitment success of the tree dominant species mainly depends on plant competition mechanisms operating at fine spatial scale, that may hinder resource availability during the former years after the disturbance. Data acquisition at very high spatial resolution from unmanned aerial vehicles (UAV) have promoted new opportunities for understanding context-dependent competition processes in post-fire environments. Here, we explored the potentiality of UAV-borne data for assessing inter-specific competition effects of understory woody vegetation on pine saplings, as well as intra-specific interactions of neighboring saplings, across three burned landscapes located along a climatic/productivity gradient in the Iberian Peninsula. Geographic object-based image analysis (GEOBIA), including multiresolution segmentation and support vector machine (SVM) classification, was used to map pine saplings and understory shrubs at species level. Input data were, on the one hand, multispectral (11.31 cm·pixel−1) and Structure-from-Motion (SfM) canopy height model (CHM) data fusion, hereafter MS-CHM, and, on the other, RGB (3.29 cm·pixel−1) and CHM data fusion, hereafter RGB-CHM. A Random Forest (RF) regression algorithm was used to evaluate the effects of neighborhood competition on the relative growth in height of 50 pine saplings randomly sampled across the MS-CHM classified map. Circular plots of 3 m radius were set from the centroid of each target pine sapling to measure percentage cover, mean height of all individuals in the plot and mean height of individuals contacting the target sapling. Competing shrub species were differentiated according to their fire-adaptive traits (i.e. seeders vs resprouters). Object-based image classification applied on MS-CHM yielded higher overall accuracy for the three sites (83.67% ± 3.06%) than RGB-CHM (74.33% ± 3.21%). Intra-specific competitive effects were not detected, whereas increasing cover and height of shrub neighbors had a significant non-linear impact on the growth on pine saplings across the study sites. The strongest competitive effects of seeder shrubs occurred in open areas with low vegetation cover and fuel continuity, following a gap-dependent model. The non-linear relationships evidenced in this study between the structure of neighboring shrubs and the growth of pine seedlings/saplings have profound implications for considering possible competing thresholds in post-fire decision-making processes. These results endorse the use of UAV multispectral and SfM photogrammetry as a valuable post-fire management tool for measuring accurately the effect of competition in heterogeneous burned landscapes.

Interspecific relationships between submerged and emergent aquatic plants along a nitrogen gradient in a mesocosm experiment

The responses of plant populations and communities to environmental factors play a key role in the ecological protection and restoration of lakes. However, little is known about how interspecific relationships respond to environmental gradients, especially for relationships between different growth forms such as submerged and emergent aquatic plants in shallow lakes, which can further affect species composition as community dynamics. We carried out a mesocosm experiment to investigate the responses of two focal aquatic plants (Ceratophyllum demersum and Phragmites australis) at two density levels and six levels of total nitrogen (TN) levels. Our results suggested that interspecific competition exist between C. demersum and P. australis, especially at high nitrogen levels. The competition relationship was mainly influenced by variations of relative growth rates of C. demersum and population density of P. australis along the nitrogen gradient. The interspecific neighbor effect on C. demersum shifted from facilitation to competition as TN increased, whereas on P. australis showed no significant facilitation effect along the TN gradient. Ceratophyllum demersum and P. australis adopted stress-tolerance and competition strategies for nitrogen, respectively, in co-culture. As a result, the dominant species in the plant community is likely to shift from the submerged macrophyte (C. demersum) to the emergent macrophyte (P. australis) as TN increases. Moderate TN (2.5 mg/L) can potentially support high biodiversity in macrophyte-dominated shallow lakes in our study. This finding has implications for different community composition at different nitrogen levels. Furthermore, it has important implications for protecting biodiversity and guiding vegetation restoration in shallow lakes.

The evolution of size-dependent competitive interactions promotes species coexistence.

Theory indicates that competing species coexist in a community when intraspecific competition is stronger than interspecific competition. When body size determines the outcome of competitive interactions between individuals, coexistence depends also on how resource use and the ability to compete for these resources change with body size. Testing coexistence theory in size-structured communities, therefore, requires disentangling the effects of size-dependent competitive abilities and niche shifts. Here, we tested the hypothesis that the evolution of species- and size-dependent competitive asymmetries increased the likelihood of coexistence between interacting species. We experimentally estimated the effects of size-dependent competitive interactions on somatic growth rates of two interacting fish species, Trinidadian guppies Poecilia reticulata and killifish Rivulus hartii. We controlled for the effects of size-dependent changes in the niche at two competitive settings representing the early (allopatric) and late (sympatric) evolutionary stages of a killifish-guppy community. We fitted the growth data to a model that incorporates species- and size-dependent competitive asymmetries to test whether changes in the competitive interactions across sizes increased the likelihood of species coexistence from allopatry to sympatry. We found that guppies are competitively superior to killifish but were less so in sympatric populations. The decrease in the effects of interspecific competition on the fitness of killifish and increase in the interspecific effect on guppies' fitness increased the likelihood that sympatric guppies and killifish will coexist. However, while the competitive asymmetries between the species changed consistently between allopatry and sympatry between drainages, the magnitude of the size-dependent competitive asymmetries varied between drainages. These results demonstrate the importance of integrating evolution and trait-based interactions into the research on how species coexist.

Comparative lipidomic analysis of Chlorella stigmatophora and Hemiselmis cf. andersenii in response to nitrogen-induced changes

The current focus of algae biotechnology is the production of high-value lipids, and its improvement by employing abiotic perturbations such as nitrogen-induced changes. In the present study, the growth dynamics, nitrogen uptake, pigments, and lipid composition of Chlorellla stigmatophora and Hemiselmis cf. andersenii were studied, in response to low (LN), medium (MN) and high (HN) nitrogen supplementations. Both microalgae responded to increased nitrogen levels by increasing their nitrogen uptake rate and pigment content. However, for lipid accumulation, C. stigmatophora presented a different pattern (LN: 16.56% > MN: 11.51% > HN: 10.95%) to that of H. cf. andersenii (MN: 15.37% > HN: 13.06% > LN: 6.71%). Untargeted gas chromatography–mass spectrometry analysis allowed the visualization of the biochemical diversity of C. stigmatophora and H. cf. andersenii, as well as differences in lipid regulation upon nitrogen-induced changes among species. For instance, glycosyl sterols were only detected for C. stigmatophora samples grown under MN and HN conditions. Moreover, lipid analysis of H. cf. andersenii, before and after alkaline hydrolysis, suggests that wax esters play a key role in the response of this microalga to high nitrogen levels. The cultivation of H. cf. andersenii at MN and HN was shown to be ideal for providing a rich source of ω3 and polyunsaturated fatty acids for nutraceutical purposes. The hierarchical cluster analysis showed the differential intra- and interspecific effects of nitrogen on lipid composition. The diverse ways by which both microalgae responded to nitrogen-induced changes highlighted the influence of phylogeny on the carbon flux through metabolic networks, and accumulation.

Limitations of current knowledge about the ecology of Grey Foxes hamper conservation efforts

Species-specific conservation is important for maintaining the integrity of ecological communities but is dependent on sufficiently understanding multiple aspects of a species’ ecology. Species-specific data are commonly lacking for species in geographic areas with little research and species perceived to have insufficient charisma or economic importance. Despite their widespread distribution across central and North America and status as a furbearing mammal, little is known about the ecology of Grey Foxes Urocyon cinereoargenteus compared to other species of furbearing mammals. To understand what is known about this species, especially factors affecting population dynamics, we performed a systematic review of the scientific literature. We found 234 studies about Grey Foxes, with studies increasing substantially over time but with geographic gaps in the Great Plains and most of Mexico and central America. Most studies we reviewed examined relative abundance or occupancy (n= 35), habitat associations (n= 30), primarily as part of larger mammalian community studies, or spatiotemporal effects of other mammalian carnivores (n= 19), predominately Coyote Canis latrans. Grey Foxes were primarily forest-associated although associations with specific forest communities or anthropogenically disturbed habitats varied among studies. Multiple studies across ecoregions reported this fox as among both the most- and least-abundant mammalian carnivore. The inter-specific effects of Coyote were often, but not exclusively, negative and were likely mediated by landscape composition and human development. Importantly, very few studies examined population-effects of coyotes on Grey Foxes. Studies of population trends, demographics, and space use of Grey Foxes were comparatively rare and small inter- and intra-study sample sizes limited our ability to infer broader patterns. We suggest multiple avenues for future research to better understand the population status of this species throughout their range.

Intra-and inter-specific competition effects on survival and growth of juvenile Procambarus acutus acutus and Procambarus clarkii

Four similar sizes eastern white river crayfish (Procambarus acutus acutus) and red swamp crayfish (Procambarus clarkii) were stocked separately to determine intra and inter-specific-competition. Three treatment levels were used three treatment levels, with six replicates tanks each with stand green rice (representing a stocking density of approximately 21 individuals per m2). This study was carried out during 90 days to determine growth and survival rate. Results showed that the growth of P. acutus acutus in the interspecific treatment tank was found higher than those grown in the intraspecific-treatment tanks. For P. clarkii, no significant differences in growth (estimated from the mean Total length, TL) were detected between treatments. The survival of the two species was the same up to the first 60 days of the experiment, while the difference in survival was only noticeable at 90 days. The survival rate of P. clarkii in the intraspecific-treatment tanks (55.0%) was higher than in the interspecific tanks (26.7%) treatment, while the survival of P. acutus acutus was found similar in two treatments. It was achieved higher survival, faster growth and larger size in P. a. acutus than P. clarkii when grown in the tank study. Size of body was important in determining competitive interactions between the two species.