G. Evelyn Hutchinson more than a half century ago proposed that one could characterize the ecological niche of a species as an abstract mapping of population dynamics onto an environmental space, the ...axes of which are abiotic and biotic factors that influence birth and death rates. If a habitat has conditions within a species' niche, a population should persist without immigration from external sources, whereas if conditions are outside the niche, it faces extinction. Analyses of species' niches are essential to understanding controls on species' geographical range limits and how these limits might shift in our rapidly changing world. Recent developments in ecology and evolutionary biology suggest it is time to revisit and refine Hutchinson's niche concept. After reviewing techniques for quantifying niches, I examine subtleties that arise because of impacts species have on their own environments, the density-dependent modulation of how individuals experience environments, and the interplay of dispersal and temporal heterogeneity in determining population persistence. Moreover, the evolutionary record over all time scales reveals a spectrum of rates of change in species' niches, from rapid niche evolution to profound niche conservatism. Substantial challenges revolving around the evolutionary dimension of the Hutchinsonian niche include quantifying the magnitude of evolved intraspecific and clade-level variation in niches and understanding the factors that govern where along the spectrum of potential evolutionary rates any given lineage lies. A growing body of theory provides elements of a conceptual framework for understanding niche conservatism and evolution, paving the way for an evolutionary theory of the niche.
Apparent Competition Holt, Robert D; Bonsall, Michael B
Annual review of ecology, evolution, and systematics,
11/2017, Letnik:
48, Številka:
1
Journal Article
Recenzirano
Most species have one or more natural enemies, e.g., predators, parasites, pathogens, and herbivores, among others. These species in turn typically attack multiple victim species. This leads to the ...possibility of indirect interactions among those victims, both positive and negative. The term apparent competition commonly denotes negative indirect interactions between victim species that arise because they share a natural enemy. This indirect interaction, which in principle can be reflected in many facets of the distribution and abundance of individual species and more broadly govern the structure of ecological communities in time and space, pervades many natural ecosystems. It also is a central theme in many applied ecological problems, including the control of agricultural pests, harvesting, the conservation of endangered species, and the dynamics of emerging diseases. At one end of the scale of life, apparent competition characterizes intriguing aspects of dynamics within individual organisms-for example, the immune system is akin in many ways to a predator that can induce negative indirect interactions among different pathogens. At intermediate scales of biological organization, the existence and strength of apparent competition depend upon many contingent details of individual behavior and life history, as well as the community and spatial context within which indirect interactions play out. At the broadest scale of macroecology and macroevolution, apparent competition may play a major, if poorly understood, role in the evolution of species' geographical ranges and adaptive radiations.
Predicting the impacts of climate change on species is one of the biggest challenges that ecologists face. Predictions routinely focus on the direct effects of climate change on individual species, ...yet interactions between species can strongly influence how climate change affects organisms at every scale by altering their individual fitness, geographic ranges and the structure and dynamics of their community. Failure to incorporate these interactions limits the ability to predict responses of species to climate change. We propose a framework based on ideas from global-change biology, community ecology, and invasion biology that uses community modules to assess how species interactions shape responses to climate change.
A large array of species distribution model (SDM) approaches has been developed for explaining and predicting the occurrences of individual species or species assemblages. Given the wealth of ...existing models, it is unclear which models perform best for interpolation or extrapolation of existing data sets, particularly when one is concerned with species assemblages. We compared the predictive performance of 33 variants of 15 widely applied and recently emerged SDMs in the context of multispecies data, including both joint SDMs that model multiple species together, and stacked SDMs that model each species individually combining the predictions afterward. We offer a comprehensive evaluation of these SDM approaches by examining their performance in predicting withheld empirical validation data of different sizes representing five different taxonomic groups, and for prediction tasks related to both interpolation and extrapolation. We measure predictive performance by 12 measures of accuracy, discrimination power, calibration, and precision of predictions, for the biological levels of species occurrence, species richness, and community composition. Our results show large variation among the models in their predictive performance, especially for communities comprising many species that are rare. The results do not reveal any major trade-offs among measures of model performance; the same models performed generally well in terms of accuracy, discrimination, and calibration, and for the biological levels of individual species, species richness, and community composition. In contrast, the models that gave the most precise predictions were not well calibrated, suggesting that poorly performing models can make overconfident predictions. However, none of the models performed well for all prediction tasks. As a general strategy, we therefore propose that researchers fit a small set of models showing complementary performance, and then apply a cross-validation procedure involving separate data to establish which of these models performs best for the goal of the study.
Understanding how landscape characteristics affect biodiversity patterns and ecological processes at local and landscape scales is critical for mitigating effects of global environmental change. In ...this review, we use knowledge gained from human-modified landscapes to suggest eight hypotheses, which we hope will encourage more systematic research on the role of landscape composition and configuration in determining the structure of ecological communities, ecosystem functioning and services. We organize the eight hypotheses under four overarching themes. Section A: ‘landscape moderation of biodiversity patterns' includes (1) the landscape species pool hypothesis—the size of the landscape-wide species pool moderates local (alpha) biodiversity, and (2) the dominance of beta diversity hypothesis—landscape-moderated dissimilarity of local communities determines landscape-wide biodiversity and overrides negative local effects of habitat fragmentation on biodiversity. Section B: ‘landscape moderation of population dynamics' includes (3) the cross-habitat spillover hypothesis—landscape-moderated spillover of energy, resources and organisms across habitats, including between managed and natural ecosystems, influences landscape-wide community structure and associated processes and (4) the landscape-moderated concentration and dilution hypothesis—spatial and temporal changes in landscape composition can cause transient concentration or dilution of populations with functional consequences. Section C: ‘landscape moderation of functional trait selection’ includes (5) the landscape-moderated functional trait selection hypothesis—landscape moderation of species trait selection shapes the functional role and trajectory of community assembly, and (6) the landscape-moderated insurance hypothesis—landscape complexity provides spatial and temporal insurance, i.e. high resilience and stability of ecological processes in changing environments. Section D: ‘landscape constraints on conservation management' includes (7) the intermediate landscape-complexity hypothesis—landscape-moderated effectiveness of local conservation management is highest in structurally simple, rather than in cleared (i.e. extremely simplified) or in complex landscapes, and (8) the landscape-moderated biodiversity versus ecosystem service management.
Integrating Biogeography with Contemporary Niche Theory Godsoe, William; Jankowski, Jill; Holt, Robert D. ...
Trends in ecology & evolution (Amsterdam),
July 2017, 2017-Jul, 2017-07-00, 20170701, Letnik:
32, Številka:
7
Journal Article
Recenzirano
Odprti dostop
There is no consensus on when biotic interactions impact the range limits of species. Starting from MacArthur’s use of invasibility to understand how biotic interactions influence coexistence, here ...we examine how biotic interactions shape species distributions. Range limits emerge from how birth, death, and movement rates vary with the environment. We clarify some basic issues revolving around niche definitions, illustrated with simple resource–consumer theory. We then highlight two different avenues for linking community theory and range theory; the first based on calculating the effects of biotic interactions on range limits across scales and landscape configurations, and the second based on aggregate measures of diffuse interactions and network strength. We conclude with suggestions for a future research agenda.
We show how analyses of species coexistence can be used determine when biotic interactions shape range limits.
Coexistence theory predicts that range limits occur when the intrinsic growth rate of a species balances the effect of biotic interactions on population growth.
To study this empirically, the growth rate of a species should be measured when it is rare, with and without biotic interactions.
These insights generalize across spatial scales.
Trophic Downgrading of Planet Earth Estes, James A.; Terborgh, John; Brashares, Justin S. ...
Science,
07/2011, Letnik:
333, Številka:
6040
Journal Article
Recenzirano
Odprti dostop
Until recently, large apex consumers were ubiquitous across the globe and had been for millions of years. The loss of these animals may be humankind's most pervasive influence on nature. Although ...such losses are widely viewed as an ethical and aesthetic problem, recent research reveals extensive cascading effects of their disappearance in marine, terrestrial, and freshwater ecosystems worldwide. This empirical work supports long-standing theory about the role of top-down forcing in ecosystems but also highlights the unanticipated impacts of trophic cascades on processes as diverse as the dynamics of disease, wildfire, carbon sequestration, invasive species, and biogeochemical cycles. These findings emphasize the urgent need for interdisciplinary research to forecast the effects of trophic downgrading on process, function, and resilience in global ecosystems.
Toward ecoevolutionary dynamics Sigmund, Karl; Holt, Robert D
Proceedings of the National Academy of Sciences - PNAS,
03/2021, Letnik:
118, Številka:
9
Journal Article
Over the last several decades, there has been a growing appreciation of the importance of nonequilibrial phenomena and transient dynamics in explaining the structure of ecological communities. This ...paper provides an overview of theoretical themes related to resource pulses. Theoretical models suggest short-term responses to a single pulse can qualitatively differ from longer-term responses. Recurrent resource pulses can alter community structure, permitting coexistence that otherwise would not occur, or hamper coexistence mechanisms effective in stable environments. For a given resource input, system responses can be more dramatic with short pulses. Resource pulses can cause transitions between alternative states. Dispersal permits species to exploit locally sporadic resource pulses and persist in environments that on average are unsuitable. All these issues are ripe for further theoretical explorations.
It is widely recognized that ecological dynamics influence evolutionary dynamics, and conversely that evolutionary changes alter ecological processes. Because fragmentation impacts all biological ...levels (from individuals to ecosystems) through isolation and reduced habitat size, it strongly affects the links among evolutionary and ecological processes such as population dynamics, local adaptation, dispersal and speciation. Here, we review our current knowledge of the eco‐evolutionary dynamics in fragmented landscapes, focusing on both theory and experimental studies. We then suggest future experimental directions to study eco‐evolutionary dynamics and/or feedbacks in fragmented landscapes, especially to bridge the gap between theoretical predictions and experimental validations.
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