Script for mathematical models - Resource intensive;Script for mathematical models - Resource light;Simulation model analysis;Simulation models;Readme from Suppression force-fields and diffuse competition: competition de-escalation is an evolutionarily stable strategy

Competition theory is founded on the premise that individuals benefit from harming their competitors, which helps them secure resources and prevent inhibition by neighbours. When multiple individuals compete, however, competition has complex indirect effects that reverberate through competitive neighbourhoods. The consequences of such ‘diffuse’ competition are poorly understood. For example, competitive effects may dilute as they propagate through a neighbourhood, weakening benefits of neighbour suppression. Another possibility is that competitive effects may rebound on strong competitors, as their inhibitory effects on their neighbours benefit other competitors in the community. Diffuse competition is unintuitive in part because we lack a clear conceptual framework for understanding how individual interactions manifest in communities of multiple competitors. Here, I use mathematical and agent-based models to illustrate that diffuse interactions—as opposed to direct pairwise interactions—are likely the dominant mode of interaction among multiple competitors. Consequently, competitive effects may regularly rebound, incurring fitness costs under certain conditions, especially when kin-kin interactions are common. These models provide a powerful framework for investigating competitive ability and its evolution and produce clear predictions in ecologically realistic scenarios

Data from: Seed and seedling traits have strong impacts on establishment of a perennial bunchgrass in invaded semi-arid systems

1. Many restoration projects use seeds to found new populations, and understanding phenotypic traits associated with seedling establishment in disturbed and invaded communities is important for restoration efforts worldwide. Focusing on the perennial grass Elymus elymoides, a native species common to sagebrush steppe communities in the Western United States, we asked if seed and seedling traits could predict field establishment. 2. We collected seeds from 34 populations from the western Great Basin. In greenhouse studies, we measured variation in seed and seedling characteristics of wild populations and one cultivar. We also quantified abiotic conditions at the collection location and asked if these characteristics predicted survival and other fitness metrics at five planting sites. Planting sites were all near-monocultures of the invasive annual grass Bromus tectorum, and all sites experienced similar, below-average precipitation during the experiment. 3. Phenotypic traits were strongly correlated with performance across all sites, with remarkably high predictive power. Seeds from populations with longer roots, larger seeds, and earlier emergence were significantly more likely to survive the first growing season (R2 = 0.66, P <0.0001). In contrast, while some abiotic variables at the collection location (e.g. 30 year average summer precipitation and fall minimum temperatures) were associated with field performance at some sites, abiotic variables explained less variation in performance than traits (average R2 = 0.22). Despite the low predictive power of abiotic variables, populations that performed best at each field site were from locations with climate variables similar to planting sites. 4. Synthesis and applications. The best seed sources for restoration of E. elymoides in invaded sites were populations with longer roots, larger seeds, and earlier emergence. These easily-measured traits were strong predictors of survival in disturbed field sites. While the most successful populations were found in areas with similar abiotic conditions as planting sites, there was phenotypic variation even among populations originating from locations with similar conditions. Thus, our results indicate that abiotic conditions are important considerations when selecting seeds, but these conditions may not sufficiently predict which populations will establish. Understanding population differences in seedling functional traits can improve predictions of restoration success

Data from: Response of bluebunch wheatgrass to invasion: differences in competitive ability among invader-experienced and naïve populations

1. Invasive species may alter selective pressures on native plant populations, and there is some evidence that competition with invasive plants may lead to differences in competitive ability between populations that have experienced invasion and those that have not. Previous results have varied among species but also among populations of the same species. 2. We conducted a greenhouse experiment to determine whether there was variation in traits, or in ability to tolerate or suppress an invasive species, among populations of a common native grass that had different histories of exposure to competition from an invasive species. Specifically, we grew seeds of a native grass (Pseudoroegneria spicata) collected from 14 wild populations (six from invaded populations and eight from uninvaded populations) and a cultivar (Anatone) alone or in competition with the invasive species (Centaurea stoebe) and measured traits of both species during and at the end of a 100-day growing period. 3. Pseudoroegneria spicata seedlings from invader-experienced populations had more leaves than invader-naïve populations, and juvenile plants from experienced populations were less affected by competition with C. stoebe than were plants from naïve populations. 4. There were significant differences in traits among populations at the seedling and juvenile life stages, and at both life stages, variation among populations was greater than variation among experience types. 5. The most predictive traits of P. spicata tolerance to competition were number of leaves (seedling and juvenile stage), and total and root biomass (juvenile only). No traits significantly predicted suppression of C. stoebe. 6. There was not a significant relationship between a population’s suppression of C. stoebe and its tolerance of competition. 7. Our results suggest that in P. spicata, invasion selects for larger plants and traits that can influence tolerance of competition. If land managers are interested in identifying highly competitive seed sources for revegetation in invaded areas, both population and invader-experience type should be considered. Since tolerance and suppression do not appear to be related in P. spicata, seed source selection should be driven by the element of competitive ability (either tolerance or suppression) that is most important to project goals

Early Sibling Conflict May Ultimately Benefit the Family

Relatives often interact differently with each other than with nonrelatives, and whether kin cooperate or compete has important consequences for the evolution of mating systems, seed size, dispersal, and competition. Previous research found that the larger of the size dimorphic seeds produced by the annual plant Aegilops triuncialis suppressed germination of their smaller sibs by 25%-60%. Here, we found evidence for kin recognition and sibling rivalry later in life among Aegilops seedlings that places seed-seed interactions in a broader context. In experiments with size dimorphic seeds, seedlings reduced the growth of sibling seedlings by ∼40% but that of nonsibling seedlings by ∼25%. These sequential antagonistic interactions between seeds and then seedlings provide insight into conflict and cooperation among kin. Kin-based conflict among seeds may maintain dormancy for some seeds until the coast is clear of more competitive siblings. If so, biotically induced seed dormancy may be a unique form of cooperation, which increases the inclusive fitness of maternal plants and offspring by minimizing competition among kin.National Science Foundation (NSF)National Science Foundation (NSF) [OIA-1757351]; NSFNational Science Foundation (NSF) [DGE-1143953]12 month embargo; published online: 14 August 2019This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Appendix A. Tables containing results of PCA on climate data and analyses of treatment on plant and soil nutrients, and figures showing comparison of actual and predicted monoculture yield and ΔRY, and effects of monoculture yield and home climate on per-capita biomass.

Tables containing results of PCA on climate data and analyses of treatment on plant and soil nutrients, and figures showing comparison of actual and predicted monoculture yield and ΔRY, and effects of monoculture yield and home climate on per-capita biomass

Effects of species interactions on the potential for evolution at species' range limits

Species’ ranges are limited by both ecological and evolutionary constraints. While there is a growing appreciation that ecological constraints include interactions among species, like competition, we know relatively little about how interactions contribute to evolutionary constraints at species' niche and range limits. Building on concepts from community ecology and evolutionary biology, we review how biotic interactions can influence adaptation at range limits by impeding the demographic conditions that facilitate evolution (which we term a ‘demographic pathway to adaptation’), and/or by imposing evolutionary trade-offs with the abiotic environment (a ‘trade-offs pathway’). While theory for the former is well-developed, theory for the trade-offs pathway is not, and empirical evidence is scarce for both. Therefore, we develop a model to illustrate how fitness trade-offs along biotic and abiotic gradients could affect the potential for range expansion and niche evolution following ecological release. The model shows that which genotypes are favoured at species' range edges can depend strongly on the biotic context and the nature of fitness trade-offs. Experiments that characterize trade-offs and properly account for biotic context are needed to predict which species will expand their niche or range in response to environmental change.ISSN:0962-8436ISSN:1471-2970ISSN:0080-462

Invasion response data

Data used to determine population, invasion experience, and treatment differences in traits and relative interaction index (RII), as well as relationship between suppression and tolerance, for bluebunch wheatgrass populations around the Missoula valley, MT, USA

Data from: Reconstructing changes in the genotype, phenotype, and climatic niche of an introduced species

An introduced species must contend with enormous environmental variation in its introduced range. In this study, we use niche models and ordination analyses to reconstruct changes in genotype, phenotype, and climatic niche of Johnsongrass (Sorghum halepense), which is regarded as one of the world's most threatening invasive plants. In the United States, Johnsongrass has rapidly evolved within- and among-population genetic diversity; our results show that genetic differentiation in expanding Johnsongrass populations has resulted in phenotypic variation that is consistent with habitat and climatic variation encountered during its expansion. Moreover, Johnsongrass expanded from agricultural to non-agricultural habitat, and now, despite occupying overlapping ranges, extant agricultural and non-agricultural populations are genetically and phenotypically distinct and manifest different plastic responses when encountering environmental variation. Non-agricultural accessions are broadly distributed in climatic and geographic space and their fitness traits demonstrate plastic responses to common garden conditions that are consistent with local specialization. In contrast, agricultural accessions demonstrate “general purpose” plastic responses and have more restricted climatic niches and geographic distributions. They also grow much larger than non-agricultural accessions. If these differences are adaptive, our results suggest that adaptation to local habitat variation plays a crucial role in the ecology of this invader. Further, its success relates to its ability to succeed on dual fronts, by responding simultaneously to habitat and climate variability and by capitalizing on differential responses to these factors during its range expansion