American Naturalist最新文献

AbstractIt is increasingly evident that most interactions are not static and move along a continuum ranging from pure mutualism (i.e., in which each species in the interaction has a net benefit in the long term) to pure antagonism (i.e., in which each species in the interaction has a net damage in the long term). Despite numerous experimental and theoretical works on this concept, predicting interaction outcomes within an ecological community continues to pose a significant challenge. This article aims to tackle this challenge by presenting a theoretical methodology for predicting the interaction outcomes within the common mutualism-antagonism modeling framework. Specifically, my main finding is to describe the influence of the population abundance of the species, the interaction effects, and the ecological context on the interaction outcomes and to quantify their relative contribution. I found that the interaction outcomes depend on the number of interacting species. In particular, when the number of interacting species increases, the trend is to skip situations where all species benefit from the interactions.

AbstractFor as long as ecology has existed, ecologists have struggled to reconcile natural history and mathematical models. This article revisits Gause's 1934 book, The Struggle for Existence, which effectively bridged their divide in his time by integrating insights from the then-separate natural history niche theory and the demographic Lotka-Volterra model. Gause's integration was based on a compelling verbal argument in which he reinterpreted the competition coefficient in terms of the niche concept. This interpretation was highly influential and was later embedded in models of modern coexistence theory. The discussion will compare Gause's verbal integration with current modeling-based approaches. While uncommon today, it will be argued that Gause's original approach carries unique advantages and remains relevant to contemporary ecology.

AbstractRecent developments in competition theory-namely, modern coexistence theory (MCT)-have aided empiricists in formulating tests of species persistence, coexistence, and evolution from simple to complex community settings. However, the parameters used to predict competitive outcomes, such as interaction coefficients, invasion growth rates, and stabilizing differences, remain biologically opaque, making findings difficult to generalize across ecological settings. This article is structured around five goals toward clarifying MCT by first making a case for the modern-day utility of MacArthur's consumer-resource model, a model with surprising complexity and depth: (i) to describe the model in uniquely accessible language, deciphering the mathematics toward cultivating deeper biological intuition about competition's inner workings regardless of what empirical toolkit one uses; (ii) to provide translation between biological mechanisms from MacArthur's model and parameters used to predict coexistence in MCT; (iii) to make explicit important but understated assumptions of MacArthur's model in plain terms; (iv) to provide empirical recommendations; and (v) to examine how key ecological concepts (e.g., r/K-selection) can be understood with renewed clarity through MacArthur's lens. We end by highlighting opportunities to explore mechanisms in tandem with MCT and to compare and translate results across ecological currencies toward a more unified ecological science.

AbstractA clear longitudinal gradient in species richness across oceans is observed in extant marine fishes, with the Indo-Pacific exhibiting the greatest diversity. Three non-mutually-exclusive evolutionary hypotheses have been proposed to explain this diversity gradient: time for speciation, center of accumulation, and in situ diversification rates. Using the morphologically disparate syngnatharians (seahorses, dragonets, goatfishes, and relatives) as a study system, we tested these hypotheses and additionally assessed whether patterns of morphological diversity are congruent with species richness patterns. We used well-sampled phylogenies and a suite of phylogenetic comparative methods (including a novel phylogenetically corrected Kruskal-Wallis test) that account for various sources of uncertainty to estimate rates of lineage diversification and morphological disparity within all three major oceanic realms (Indo-Pacific, Atlantic, and eastern Pacific), as well as within the Indo-Pacific region. We find similar lineage diversification rates across regions, indicating that increased syngnatharian diversity in the Indo-Pacific is due to earlier colonizations from the Tethys Sea followed by in situ speciation and more frequent colonizations during the Miocene coinciding with the formation of coral reefs. These results support both time for speciation and center of accumulation hypotheses. Unlike species richness unevenness, shape disparity and evolutionary rates are similar across oceans because of the early origin of major body plans and their subsequent spread via colonization rather than in situ evolution. Our results illustrate how species richness patterns became decoupled from morphological disparity patterns during the formation of a major biodiversity hot spot.

AbstractThe metapopulation concept offers significant explanatory power in ecology and evolutionary biology. Metapopulations, a set of spatially distributed populations linked by dispersal, and their community and ecosystem level analogs, metacommunity and meta-ecosystem models, tend to be more stable regionally than locally. This fact is largely attributable to the interplay of spatiotemporal heterogeneity and dispersal (the inflationary effect). We highlight this underappreciated (but essential) role of spatiotemporal heterogeneity in metapopulation biology, present a novel expression for quantifying and defining the inflationary effect, and provide a mechanistic interpretation of how it arises and impacts population growth and abundance. We illustrate the effect with examples from infectious disease dynamics, including the hypothesis that policy decisions made during the COVID-19 pandemic generated spatiotemporal heterogeneity that enhanced the spread of disease. We finish by noting how spatiotemporal heterogeneity generates emergent population processes at large scales across many topics in the history of ecology, as diverse as natural enemy-victim dynamics, species coexistence, and conservation biology. Embracing the complexity of spatiotemporal heterogeneity is vital for future research on the persistence of populations.

AbstractThe metabolic theory of ecology (MTE) aims to link biophysical constraints on individual metabolic rates to the emergence of patterns at the population and ecosystem scales. Because MTE links temperature's kinetic effects on individual metabolism to ecological processes at higher levels of organization, it holds great potential to mechanistically predict how complex ecological systems respond to warming and increased temperature fluctuations under climate change. To scale up from individuals to ecosystems, applications of classical MTE implicitly assume that focusing on steady-state dynamics and averaging temperature responses across individuals and populations adequately capture the dominant attributes of biological systems. However, in the context of climate change, frequent perturbations from steady state and rapid changes in thermal performance curves via plasticity and evolution are almost guaranteed. Here, we explain how some of the assumptions made when applying MTE's simplest canonical expression can lead to blind spots in understanding how temperature change affects biological systems and how this presents an opportunity for formal expansion of the theory. We review existing advances in this direction and provide a decision tree for identifying when dynamic modifications to classical MTE are needed for certain research questions. We conclude with empirical and theoretical challenges to be addressed in a more dynamic MTE for understanding biological change in an increasingly uncertain world.

AbstractResolving the degree to which environmental (direct) versus genetic (indirect) benefits shape female mate choice is a long-standing challenge, particularly for socially monogamous species where male environmental and genetic contributions are difficult to disentangle. This study combines long-term population monitoring with quantitative genetic analyses in a socially monogamous but sexually promiscuous Australian songbird to demonstrate that female mating preferences are driven by nongenetic environmental benefits that increase the fitness of both the female and her offspring. Male Red-backed Fairywrens (Malurus melanocephalus) flexibly breed in either ornamented or unornamented plumage, and females consistently prefer ornamented males. Females paired with ornamented males bred earlier and allocated more to current reproduction yet experienced higher survival and lifetime fitness. Furthermore, these females produced more grand-offspring because their early-born sons were more likely to be ornamented and to breed successfully than the later-born sons of females with unornamented partners. Quantitative genetic models showed lifetime fitness was best explained by parental environment rather than genetic effects. Mating preferences in this system are maintained by a combination of primary environmental benefits that increase the lifetime fitness of choosy females and secondary environmental benefits that increase the multigenerational fitness of those females through enhanced offspring quality and performance.

AbstractAs scientists, our collective goal is to make scientific progress in the pursuit of an absolute truth about the nature of the universe, through a feedback loop of observation, theory, and experimentation. What if a major limit to progress is not the science itself but rather in how broadly scientific ideas can be understood? In this introduction to a special feature, we highlight four articles, each tasked with demystifying a key theory in ecology for a general audience, with a special focus on aspects of each theory that have been misunderstood, misapplied, or underappreciated in some important way. These four theories are metabolic theory, competition theory based on consumer-resource models, mechanisms of coexistence in fluctuating environments, and metapopulation dynamics. We point out key ways in which each article applied best practices of accessible communication as well as challenges that might arise (and potential solutions for journals and authors) when attempting to publish articles with a deeper emphasis on explanation of fundamentals than a traditional article might provide.

AbstractModern coexistence theory is a dominant framework for understanding how environmental fluctuations promote species coexistence. However, assessing fluctuation-dependent mechanisms of coexistence in empirical systems-in which species have diverse life histories and environment-competition relationships-has remained challenging for many ecologists. To help empiricists and theoreticians alike build intuition for the role of fluctuation-dependent mechanisms across systems and environments, we explore how two stage-structured life histories-perennial and seedbanking annuals-differ in competition with a nonseedbanking annual across three environmental scenarios. Our scenarios delineate how species partition resources within and among years and whether competition is most intense during favorable or unfavorable periods. We use this work to link differences in vital rates and interaction strengths to patterns and mechanisms of coexistence. Fluctuation-dependent mechanisms of coexistence can be equally important for perennial species with an adult "storage" stage as for seedbanking annuals. However, coexistence outcomes differentiate between these two stage-structured strategies based on whether they experience stronger or weaker competition in favorable environments. This work sets the stage for applying coexistence theory and fluctuation-dependent partitioning frameworks to perennial and mixed stage-structure communities, facilitating understanding of how environmental variation drives species dynamics across a broader range of systems.

AbstractSpecies' interactions are shaped by their traits. Thus, we expect traits-in particular, trait (dis)similarity-to play a central role in determining whether a particular set of species coexists. Traits are, in turn, the outcome of an eco-evolutionary process summarized by a phylogenetic tree. Therefore, the phylogenetic tree associated with a set of species should carry information about the dynamics and assembly properties of the community. Many studies have highlighted the potentially complex ways in which this phylogenetic information is translated into species' ecological properties. However, much less emphasis has been placed on developing clear, quantitative expectations for community properties under a particular hypothesis. To address this gap, we couple a simple model of trait evolution on a phylogenetic tree with Lotka-Volterra community dynamics. This allows us to derive properties of a community of coexisting species as a function of the number of traits, tree topology, and the size of the species pool. Our analysis highlights how phylogenies, through traits, affect the coexistence of a set of species. Together, these results provide much-needed baseline expectations for the ways in which evolutionary history, summarized by phylogeny, is reflected in the size and structure of ecological communities.