Explore the vast range of titles available.

Human activity is causing wild populations to experience rapid trait change and local extirpation. The resulting effects on intraspecific variation could have substantial consequences for ecological processes and ecosystem services. Although researchers have long acknowledged that variation among species influences the surrounding environment, only recently has evidence accumulated for the ecological importance of variation within species. We conducted a meta-analysis comparing the ecological effects of variation within a species (intraspecific effects) with the effects of replacement or removal of that species (species effects). We evaluated direct and indirect ecological responses, including changes in abundance (or biomass), rates of ecological processes and changes in community composition. Our results show that intraspecific effects are often comparable to, and sometimes stronger than, species effects. Species effects tend to be larger for direct ecological responses (for example, through consumption), whereas intraspecific effects and species effects tend to be similar for indirect responses (for example, through trophic cascades). Intraspecific effects are especially strong when indirect interactions alter community composition. Our results summarize data from the first generation of studies examining the relative ecological effects of intraspecific variation. Our conclusions can help inform the design of future experiments and the formulation of strategies to quantify and conserve biodiversity. A meta-analysis comparing the ecological effects of variation within a species with the effects of species replacement or renewal shows that intraspecific effects may be comparable to, or sometimes stronger than, species effects.

1. Plant-soil feedbacks is becoming an important concept for explaining vegetation dynamics, the invasiveness of introduced exotic species in new habitats and how terrestrial ecosystems respond to global land use and climate change. Using a new conceptual model, we show how critical alterations in Plant-soil feedback interactions can change the assemblage of plant communities. We highlight recent advances, define terms and identify future challenges in this area of research and discuss how variations in strengths and directions of Plant-soil feedbacks can explain succession, invasion, response to climate warming and diversity-productivity relationships. 2. While there has been a rapid increase in understanding the biological, chemical and physical mechanisms and their interdependencies underlying Plant-soil feedback interactions, further progress is to be expected from applying new experimental techniques and technologies, linking empirical studies to modelling and field-based studies that can include Plant-soil feedback interactions on longer time scales that also include long-term processes such as litter decomposition and mineralization. 3. Significant progress has also been made in analysing consequences of Plant-soil feedbacks for biodiversity-functioning relationships, plant fitness and selection. 4. To further integrate Plant-soil feedbacks into ecological theory, it will be important to determine where and how observed patterns may be generalized, and how they may influence evolution. 5. Synthesis. Gaining a greater understanding of Plant-soil feedbacks and underlying mechanisms is improving our ability to predict consequences of these interactions for plant community composition and productivity under a variety of conditions. Future research will enable better prediction and mitigation of the consequences of human-induced global changes, improve efforts of restoration and conservation and promote sustainable provision of ecosystem services in a rapidly changing world.

Identifying and predicting how species ranges will shift in response to climate change is paramount for conservation and restoration. Ecological niche models are the most common method used to estimate potential distributions of species; however, they traditionally omit knowledge of intraspecific variation that can allow populations to respond uniquely to change. Here, we aim to test how population X environment relationships influence predicted suitable geographic distributions by comparing aggregated population-level models with species-level model predictions of suitable habitat within population ranges and across the species’ range. We also test the effect of two variable selection methods on these predictions–both addressing the possibility of local adaptation: Models were built with (a) a common set, and number, of predictors and, (b) a unique combination and number of predictors specific to each group’s training extent. Our study addresses the overarching hypothesis that populations have unique environmental niches, and specifically that (1) species-level models predict more suitable habitat within the ranges of genetic populations than individual models built from those groups, particularly when compared models are built with the same set of environmental predictors; and (2) aggregated genetic population models predict more suitable habitat across the species’ range than the species-level model, an = d this difference will increase when models are trained with individualized predictors. We found the species models predicted more habitat within population ranges for two of three genetic groups regardless of variable selection, and that aggregated population models predicted more habitat than species’ models, but that individualized predictors increased this difference. Our study emphasizes the extent to which changes to model predictions depend on the inclusion of genetic information and on the type and selection of predictors. Results from these modeling decisions can have broad implications for predicting population-level ecological and evolutionary responses to climate change.

Roots are essential to the strategies plants use to survive in variable environments, yet we know little of how they vary within species. Experimental conditions demonstrate that intraspecific plant root traits respond strongly to variation in the environment; however, it is unclear when these responses can be characterized as evolution in response to selective pressures of climate change over many generations. Sky Islands are model, natural climate relict ecosystems to examine climate-change driven evolution. Utilizing a common garden with replicate genotypes of Populus angustifolia (Narrowleaf cottonwood) from six Sky Island (SI) populations and nine adjacent Mountain Chain (MC) populations across three genetic provenances, we hypothesized that SI root traits have diverged due to historical isolation in warmer, drier climates. When grown in common conditions, populations originating on SI’s showed convergent evolution across three distinct genetic provenances, which was characterized by 44.16% decreased total root length, 42.64% decreased average root volume, 43.31% decreased root surface area, and significantly less root trait variation, relative to adjacent mountain chains. Convergent evolution of root traits from trees originating on SI’s is correlated with changes in mean annual precipitation and potential evapotranspiration in the field over the past ~ 125 years. These results demonstrate a consistent pattern in root trait evolution at the landscape scale and the role of climate on the evolution of root traits in a genetic and geographic context relevant to climate change.

To what extent microbial community composition can explain variability in ecosystem processes remains an open question in ecology. Microbial decomposer communities can change during litter decomposition due to biotic interactions and shifting substrate availability. Though relative abundance of decomposers may change due to mixing leaf litter, linking these shifts to the non-additive patterns often recorded in mixed species litter decomposition rates has been elusive, and links community composition to ecosystem function. We extracted phospholipid fatty acids (PLFAs) from single species and mixed species leaf litterbags after 10 and 27 months of decomposition in a mixed conifer forest. Total PLFA concentrations were 70% higher on litter mixtures than single litter types after 10 months, but were only 20% higher after 27 months. Similarly, fungal-to-bacterial ratios differed between mixed and single litter types after 10 months of decomposition, but equalized over time. Microbial community composition, as indicated by principal components analyses, differed due to both litter mixing and stage of litter decomposition. PLFA biomarkers a15∶0 and cy17∶0, which indicate gram-positive and gram-negative bacteria respectively, in particular drove these shifts. Total PLFA correlated significantly with single litter mass loss early in decomposition but not at later stages. We conclude that litter mixing alters microbial community development, which can contribute to synergisms in litter decomposition. These findings advance our understanding of how changing forest biodiversity can alter microbial communities and the ecosystem processes they mediate.

Rare species are often considered inferior competitors due to occupancy of small ranges, specific habitats, and small local populations. However, the phylogenetic relatedness and rarity level (level 1–7 and common) of interacting species in plant-plant interactions are not often considered when predicting the response of rare plants in a biotic context. We used a common garden of 25 species of Tasmanian Eucalyptus , to differentiate non-additive patterns in the biomass of rare versus common species when grown in mixtures varying in phylogenetic relatedness and rarity. We demonstrate that rare species maintain progressively positive non-additive responses in biomass when interacting with phylogenetically intermediate, less rare and common species. This trend is not reflected in common species that out-performed in monocultures compared to mixtures. These results offer predictability as to how rare species’ productivity will respond within various plant-plant interactions. However, species-specific interactions, such as those involving E . globulus , yielded a 97% increase in biomass compared to other species-specific interaction outcomes. These results are important because they suggest that plant rarity may also be shaped by biotic interactions, in addition to the known environmental and population factors normally used to describe rarity. Rare species may utilize potentially facilitative interactions with phylogenetically intermediate and common species to escape the effects of limiting similarity. Biotically mediated increases in rare plant biomass may have subsequent effects on the competitive ability and geographic occurrence of rare species, allowing rare species to persist at low abundance across plant communities. Through the consideration of species rarity and evolutionary history, we can more accurately predict plant-plant interaction dynamics to preserve unique ecosystem functions and fundamentally challenge what it means to be “rare”.

Ecological explanations for the success and persistence of invasive species vastly outnumber evolutionary hypotheses, yet evolution is a fundamental process in the success of any species. The Evolution of Increased Competitive Ability (EICA) hypothesis (Blossey and Nötzold 1995) proposes that evolutionary change in response to release from coevolved herbivores is responsible for the success of many invasive plant species. Studies that evaluate this hypothesis have used different approaches to test whether invasive populations allocate fewer resources to defense and more to growth and competitive ability than do source populations, with mixed results. We conducted a meta‐analysis of experimental tests of evolutionary change in the context of EICA. In contrast to previous reviews, there was no support across invasive species for EICA's predictions regarding defense or competitive ability, although invasive populations were more productive than conspecific native populations under noncompetitive conditions. We found broad support for genetically based changes in defense and competitive plant traits after introduction into new ranges, but not in the manner suggested by EICA. This review suggests that evolution occurs as a result of plant introduction and population expansion in invasive plant species, and may contribute to the invasiveness and persistence of some introduced species. We conducted a meta‐analysis of defense and competitive traits of invasive plant species to assess support for the Evolution of Increased Competitive Ability (EICA) hypothesis. There is no general trend across species of evolutionary reductions in defense, and evolutionary enhancement of competitive traits occured only for vegetative growth traits, not for fitness‐related traits. However, there is broad support for evolutionary changes not consistent with EICA in defensive traits and competitive traits across invasive populations of these plant species.

PurposeWhile distinct soil microbiomes and individual soil microbial taxa can alter particular plant traits under highly controlled conditions, little is known about the role of particular microbial taxa and microbial functions within complex soil microbial communities for mediating plant phenotypes or if the strength of microbial mediation of plant phenotype varies among plant species or plant phenotypic traits. Examining how the plant phenotype spectrum is influenced by the taxonomic and functional composition of complex soil microbial communities allows for a more accurate understanding of the biotic environmental drivers of plant phenotype.MethodsUsing rhizosphere soil collected from field sites, we conducted a microbiome transfer glasshouse experiment to test the hypothesis that the taxonomic and functional composition of different soil microbiomes would differentially shift growth, physiological or reproductive phenotypes of three Solidago species.ResultsWe found that soil microbiome inoculations influenced Solidago growth traits more than physiological and reproductive traits. We found that root growth of one of the Solidago species was negatively correlated with 77% of the indicator bacterial and fungal taxa from one of the soil microbiome treatments.ConclusionsSoil microbial mediation of plant phenotype varies by plant traits, is not universal across plant species, and can be associated with a small number of microbial taxa. This study illustrates that specific microbial taxa within a soil microbiome are associated with shifts in plant phenotype by pinpointing important individual microbial taxa from complex field soil microbial communities.

Summary While an appreciation of plant–soil feedbacks (PSF) continues to expand for community and ecosystem ecology, the eco‐evolutionary mechanisms and consequences of such feedbacks remain largely unknown or untested. Determining the cause and effect of plant phenotypes is central for understanding these eco‐evolutionary dynamics since phenotypes respond to soil selective gradients that are, in turn, modified by plant traits. Genetic variation in plant phenotypes can change soil processes and biotic communities; oppositely, soil gradients and microbial communities can influence the expression and evolution of plant phenotypes. Although these processes represent the two halves of genetic based PSF, research in these areas has developed independently from one another. Greater connectivity between research on ecosystem consequences of plant genetic variation and soil selective gradients that drive plant phenotypic evolution will create novel and important opportunities to link ecology and evolution in natural systems. Papers in this special feature build on the inherent ecological and evolutionary processes involved in PSF, outlining many ways to identify and test mechanisms that connect ecosystem ecology and evolution. Lay Summary

As human populations expand and land‐use change intensifies, terrestrial ecosystems experience concurrent disturbances (e.g., urbanization and fire) that may interact and compound their effects on biodiversity. In the urbanizing landscapes of the southern Appalachian region of the United States of America (US), fires in mesic forests have become more frequent in recent years. However, 80 years of forest management practices aimed at fire suppression in this region may have decreased landscape resistance or resilience to high‐severity fires. At the same time, housing development is rapidly expanding in the wildland–urban interface, creating opportunities to examine the combined effects of urbanization and fire disturbances on plant communities when fires occur. Here, we investigated how understory plant communities were affected by a fire that varied in severity at sites in Gatlinburg, TN, and in the adjacent Great Smoky Mountains National Park. Our goal was to investigate the individual and combined effects of fire and urbanization on plant community composition in the second growing season after a fire. Overall, we found a significant interaction effect of fire severity and urbanization on total plant abundance and richness, such that increasing fire severity was associated with lower abundance and richness in natural areas but higher abundance and richness in exurban areas. Shannon diversity was significantly affected by fire severity and urbanization, but not interactively. Plant composition was affected by fire severity, urbanization, and their interaction effects. Understory plant communities in exurban locations (low‐density residential areas near protected lands) were resilient following the pulse disturbance event (fire), likely because of their consistent exposure to a press disturbance (urbanization). Our study indicates a press disturbance may change the way a subsequent pulse disturbance affects plant communities. Our findings contribute new insights into how disturbances can interact to alter patterns of biodiversity in the southeastern US.