Showing papers in "The American Naturalist in 2021"
TL;DR: Hybrids are not phenotypically intermediate but rather exhibit substantial mismatch, and dominance is likely determined by the idiosyncratic evolutionary trajectories of individual traits and populations.
Abstract: Compared to those of their parents, are the traits of first-generation (F1) hybrids typically intermediate, biased toward one parent, or mismatched for alternative parental phenotypes? To a...
44 citations
TL;DR: The rapid global loss of biodiversity calls for improved predictions of how populations will evolve and respond demographically to ongoing environmental change as discussed by the authors, and the heritability (h2) of sel...
Abstract: The rapid global loss of biodiversity calls for improved predictions of how populations will evolve and respond demographically to ongoing environmental change. The heritability (h2) of sel...
27 citations
TL;DR: This article revisited the narrative behind Stebbins's "cradles" and "museums" of biodiversity and argued that the concepts of cradles and museums have outlived their utility in studies of biogeography and macroevolution and should be replaced by discussions of actual processes at play.
Abstract: In 1974, G. Ledyard Stebbins provided a metaphor illustrating how spatial gradients of biodiversity observed today are by-products of the way environment-population interactions drive species diversification through time. We revisit the narrative behind Stebbins’s “cradles” and “museums” of biodiversity to debate two points. First, the usual high-speciation versus low-extinction and tropical versus temperate dichotomies are oversimplifications of the original metaphor and may obscure how gradients of diversity are formed. Second, the way in which we use modern gradients of biodiversity to interpret the potential historical processes that generated them are often still biased by the reasons that motivated Stebbins to propose his original metaphor. Specifically, the field has not yet abandoned the idea that species-rich areas and “basal lineages” indicate centers of origin, nor has it fully appreciated the role of traits as regulators of environment-population dynamics. We acknowledge that the terms “cradles” and “museums” are popular in the literature and that terminologies can evolve with the requirements of the field. However, we also argue that the concepts of cradles and museums have outlived their utility in studies of biogeography and macroevolution and should be replaced by discussions of actual processes at play.
23 citations
TL;DR: An extensive investigation of temperature drivers from fine to coarse scales is provided, and it is demonstrated that the degree of similarity in temperatures at high and low elevations on mountains is driven by more than just absolute mountain height and latitude.
Abstract: An extension of the climate variability hypothesis is that relatively stable climate, such as that of the tropics, induces distinct thermal bands across elevation that render dispersal over...
22 citations
TL;DR: This work uses niche-based competition matrices and Lotka-Volterra models and a 10-year observational study to demonstrate that observed combinations of herbivores have an expected probability of species persistence higher than half of all potential combinations.
Abstract: Despite the rich biodiversity found in nature, it is unclear to what extent some combinations of interacting species, while conceivable in a given place and time, may never be realized. Yet...
21 citations
TL;DR: This introduction to the Special Feature on Model Systems in Ecology, Evolution, and Behavior (EEB), grappling with the question, What is a model system is begun, and the importance of communities of scientists in the success of model systems is emphasized—narrow scientific communities can restrict the model organisms themselves.
Abstract: Ecologists and evolutionary biologists are fascinated by life’s variation but also seek to understand phenomena and mechanisms that apply broadly across taxa. Model systems can help us extr...
20 citations
TL;DR: Results suggest that the specific identity of focal or neighbor species is not necessary for building well-performing fitness models that include HOIs, and grouping neighbors by even basic functional information seems sufficient to maximize model accuracy, an important outcome for the practical use of HOI-inclusive fitness models.
Abstract: Direct species interactions are commonly included in individual fitness models used for coexistence and local diversity modeling. Though widely considered important for such models, direct ...
18 citations
TL;DR: An energy budget model for simulating effects of acoustic disturbance on populations and its mechanisms are general to animal species can be used for gaining new insights into the spatiotemporal variability of animal movements and energetics that control population dynamics.
Abstract: In marine environments, noise from human activities is increasing dramatically, causing animals to alter their behavior and forage less efficiently. These alterations incur energetic costs ...
17 citations
TL;DR: This analysis shows that positive autocorrelations in demographic rates that increase fitness produce the positive environment-competition covariance in condition (i), and highlights that temporal autoc orrelations in environmental conditions can play a fundamental role in determining ecological outcomes of competing species.
Abstract: Environmental fluctuations can mediate coexistence between competing species via the storage effect. This fluctuation-dependent coexistence mechanism requires three conditions: (i) there is...
17 citations
TL;DR: A balance between degree of frugivory and visitation rates to lipid-poor and lipid-rich fruits provides a mechanism to explain specialized dispersal systems and the occurrence of certain physiological nutritional filters, ultimately helping to understand community-wide interaction patterns between birds and plants.
Abstract: The interaction between fruit chemistry and the physiological traits of frugivores is expected to shape the structure of mutualistic seed dispersal networks, but it has been understudied compared with the role of morphological trait matching in structuring interaction patterns. For instance, highly frugivorous birds (i.e., birds that have fruits as the main component of their diets), which characteristically have fast gut passage times, are expected to avoid feeding on lipid-rich fruits because of the long gut retention times associated with lipid digestion. Here, we compiled data from 84 studies conducted in the Neotropics that used focal plant methods to record 35,815 feeding visits made by 317 bird species (155 genera in 28 families) to 165 plant species (82 genera in 48 families). We investigated the relationship between the degree of frugivory of birds (i.e., how much of their diet is composed of fruit) at the genus level and their visits to plant genera that vary in fruit lipid content. We used a hierarchical modeling of species communities approach that accounted for the effects of differences in body size, bird and plant phylogeny, and spatial location of study sites. We found that birds with a low degree of frugivory (e.g., predominantly insectivores) tend to have the highest increase in visitation rates as fruits become more lipid rich, while birds that are more frugivorous tend to increase visits at a lower rate or even decrease visitation rates as lipids increase in fruits. This balance between degree of frugivory and visitation rates to lipid-poor and lipid-rich fruits provides a mechanism to explain specialized dispersal systems and the occurrence of certain physiological nutritional filters, ultimately helping us to understand community-wide interaction patterns between birds and plants.
16 citations
TL;DR: It is found that in the presence of hyperparasites, the evolutionarily optimal pathogen virulence generally shifts toward more virulent strains, which means that even the use of hyperParasites in biocontrol could be justified, since overall host mortality decreases.
Abstract: Hyperparasitism denotes the natural phenomenon where a parasite infecting a host is in turn infected by its own parasite. Hyperparasites can shape the dynamics of host-parasite interactions...
TL;DR: It is found that families showing high speciation rates contain a high proportion of species distributed in mountains, and that lineages inhabiting areas of HTC speciate faster than lineages occupying areas that are topographically less complex.
Abstract: Continental mountain areas cover 80% of global terrestrial diversity One prominent hypothesis to explain this pattern proposes t
TL;DR: This work graphically explain the qualitative phenomena previously found by numerical simulations, including the effects on community dynamics of nestedness, adaptive foraging, and pollinator invasions.
Abstract: Contemporary niche theory is a useful framework for understanding how organisms interact with each other and with their shared environment. Its graphical representation, popularized by Tilm...
TL;DR: It is demonstrated that while reduced recombination rates between adaptive loci slow down range expansions as a result of poor purging of locally deleterious alleles at the expansion front, they may also allow a species to occupy a greater range, and there is a trade-off between positive and negative effects of recombination within and between individuals.
Abstract: Previous theoretical work on range expansions over heterogeneous environments showed that there is a critical environmental gradient where range expansion stops. For populations with freely...
TL;DR: It is suggested that androgen-muscle interactions provide a conduit for convergence in sexual display behavior, potentially providing a path of least resistance for the evolution of motor performance.
Abstract: Unrelated species often evolve similar phenotypic solutions to the same environmental problem, a phenomenon known as convergent evolution. But how do these common traits arise? We address t...
TL;DR: This work validates recent theoretical findings on evolution in fluctuating environments, suggesting that the predictability of fluctuating selection pressures may play a predominant role in shaping the phenotypic variation observed across natural populations.
Abstract: Phenotypic plasticity is expected to facilitate the persistence of natural populations as global change progresses. The attributes of fluctuating environments that favor the evolution of pl...
TL;DR: This work provides a general and accessible guide that covers the basic, step-by-step process of how to approach, understand, and use ecological theory in empirical work and presents a practical tool kit for reading and understanding the mathematical aspects of ecological theory.
Abstract: A scientific understanding of the biological world arises when ideas about how nature works are formalized, tested, refined, and then tested again. Although the benefits of feedback between...
TL;DR: This work explores how the pathogen transmission mode and characteristics of a second host (disease competence and competitive ability) influence disease prevalence in a focal host and identifies general rules about how host and pathogen characteristics affect amplification/dilution.
Abstract: Biodiversity in communities is changing globally, including the gain and loss of host species in host-pathogen communities. Increased host diversity can cause infection prevalence in a foca...
TL;DR: Examination of age-related changes in sex-specific survival, reproduction, and several components of reproduction using a long-term study of a cooperatively breeding songbird finds striking differences in aging and senescence patterns between survival and reproduction as well as between reproductive traits.
Abstract: Why do senescence rates of fitness-related traits often vary dramatically? By considering the full aging trajectories of multiple traits, we can better understand how a species’ life histor...
TL;DR: Observational evidence for parasite regulation of multiple life-history trade-offs is offered, supporting the role of parasites as an important mediating factor in wild mammal populations.
Abstract: Reproduction in wild animals can divert limited resources away from immune defense, resulting in increased parasite burdens. A long-standing prediction of life-history theory states that these parasites can harm the reproductive individual, reducing its subsequent survival and fecundity, producing reproduction-fitness trade-offs. Here, we examined associations among reproductive allocation, immunity, parasitism, and subsequent survival and fecundity in a wild population of individually identified red deer (Cervus elaphus). Using path analysis, we investigated whether costs of lactation in terms of downstream survival and fecundity were mediated by changes in strongyle nematode count and mucosal antibody levels. Lactating females exhibited increased parasite counts, which were in turn associated with substantially decreased fitness in the following year in terms of overwinter survival, fecundity, subsequent calf weight, and parturition date. This study offers observational evidence for parasite regulation of multiple life-history trade-offs, supporting the role of parasites as an important mediating factor in wild mammal populations.
TL;DR: Here, it is illustrated how the strength of EWSs is determined by each species’ relationship to properties of the noise, the system’s response to that noise, and the occurrence of critical slowing down (the dynamical phenomenon that gives rise to EWS).
Abstract: Early warning signals (EWSs) have the potential to predict tipping points where catastrophic changes occur in ecological systems. However, EWSs are plagued by false negatives, leading to un...
TL;DR: It is suggested that disease can comprise an important selective pressure on animal habitat and space use and Habitat selection models, therefore, may be greatly improved by including variables that quantify infection risk and/or the infection status of individuals through time.
Abstract: Animals challenged with disease may select specific habitat conditions that help prevent or reduce infection. Whereas preinfection avoidance of habitats with a high risk of disease exposure has been documented in both captive and free-ranging animals, evidence of switching habitats after infection to support the clearing of the infection is limited to laboratory experiments. The extent to which wild animals proximately modify habitat choices in response to infection status thus remains unclear. We investigated preinfection behavioral avoidance and postinfection habitat switching using wild, radio-tracked boreal toads (Anaxyrus boreas boreas) in a population challenged with Batrachochytrium dendrobatidis (Bd), a pathogenic fungus responsible for a catastrophic panzootic affecting hundreds of amphibian species worldwide. Boreal toads did not preemptively avoid microhabitats with conditions conducive to Bd growth. Infected individuals, however, selected warmer, more open habitats, which were associated with elevated body temperature and the subsequent clearing of infection. Our results suggest that disease can comprise an important selective pressure on animal habitat and space use. Habitat selection models, therefore, may be greatly improved by including variables that quantify infection risk and/or the infection status of individuals through time.
TL;DR: In this article, the effects of climate and light environments on plumage color in the large Neotropical passerine family Furnariidae have been investigated and it was found that birds in cooler and rainier climates had darker plumage even after controlling for habitat type.
Abstract: Ecogeographic rules provide a framework within which to test evolutionary hypotheses of adaptation. Gloger's rule predicts that endothermic animals should have darker colors in warm/rainy climates. This rule also predicts that animals should be more rufous in warm/dry climates, the so-called complex Gloger's rule. Empirical studies frequently demonstrate that animals are darker in cool/wet climates rather than in warm/wet climates. Furthermore, sensory ecology predicts that, to enhance crypsis, animals should be darker in darker light environments. We aimed to disentangle the effects of climate and light environments on plumage color in the large Neotropical passerine family Furnariidae. We found that birds in cooler and rainier climates had darker plumage even after controlling for habitat type. Birds in darker habitats had darker plumage even after controlling for climate. The effects of temperature and precipitation interact so that the negative effect of precipitation on brightness is strongest in cool temperatures. Finally, birds tended to be more rufous in warm/dry habitats but also, surprisingly, in cool/wet locales. We suggest that Gloger's rule results from complementary selective pressures arising from myriad ecological factors, including crypsis, thermoregulation, parasite deterrence, and resistance to feather abrasion.
TL;DR: It is suggested that ages or stages where the importance of luck peaks are potential targets for interventions to benefit a population of concern, different from those identified by eigenvalue elasticity analysis.
Abstract: Over the course of individual lifetimes, luck usually explains a large fraction of the between-individual variation in life span or lifetime reproductive output (LRO) within a population, w...
TL;DR: A game-theory model of hierarchy formation in which individuals adjust their aggressive behaviour towards other group members through reinforcement learning is presented, finding that evolution favours individuals with high social competence, making use of individual recognition, bystander learning and, to a limited extent, generalising learned behaviour between opponents when adjusting their behaviour towardsother group members.
Abstract: Groups of social animals are often organized into dominance hierarchies that are formed through pairwise interactions. There is much experimental data on hierarchies, examining such things as winner, loser, and bystander effects, as well as the linearity and replicability of hierarchies, but there is a lack evolutionary analyses of these basic observations. Here I present a game theory model of hierarchy formation in which individuals adjust their aggressive behavior toward other group members through reinforcement learning. Individual traits such as the tendency to generalize learning between interactions with different individuals, the rate of learning, and the initial tendency to be aggressive are genetically determined and can be tuned by evolution. I find that evolution favors individuals with high social competence, making use of individual recognition, bystander observational learning, and, to a limited extent, generalizing learned behavior between opponents when adjusting their behavior toward other group members. The results are in qualitative agreement with experimental data, for instance, in finding weaker winner effects compared to loser effects.
TL;DR: It is shown how the effects of dichromatism on diversification are highly variable in direction and restricted to certain clades and phylogenetic scales.
Abstract: Sexually selected traits have long been thought to drive diversification, but support for this hypothesis has been persistently controversial. In fishes, sexually dimorphic coloration is associated with assortative mating and speciation among closely related species, as shown in classic studies. However, it is unclear whether these results can generalize to explain diversity patterns across ray-finned fishes, which contain the majority of vertebrate species and 96% of fishes. Here, we use phylogenetic approaches to test for an association between sexual dichromatism and diversification rates (speciation minus extinction) in ray-finned fishes. We assembled dichromatism data for 10,898 species, a data set of unprecedented size. We found no difference in diversification rates between monochromatic and dichromatic species when including all ray-finned fishes. However, at lower phylogenetic scales (within orders and families), some intermediate-sized clades did show an effect of dichromatism on diversification. Surprisingly, dichromatism could significantly increase or decrease diversification rates. Moreover, we found no effect in many of the clades initially used to link dichromatism to speciation in fishes (e.g., cichlids) or an effect only at shallow scales (within subclades). Overall, we show how the effects of dichromatism on diversification are highly variable in direction and restricted to certain clades and phylogenetic scales.
TL;DR: This work model sexually antagonistic alleles in eight different sex determination systems and finds that arguments 1 and 2 promote invasion and fixation of female-Beneficial and male-beneficial alleles, respectively; argument 2 also improves prospects for polymorphism.
Abstract: In haplodiploids, (1) alleles spend twice as many generations in females as in males, (2) males are never heterozygous and therefore express recessive alleles, and (3) males sire daughters but not sons. Intralocus sexual conflict therefore operates differently in haplodiploids than in diploids and shares strong similarities with loci on X (or Z) chromosomes. The common co-occurrence of all three features makes it difficult to pinpoint their respective roles. However, they do not always co-occur in nature, and missing cases can be additionally studied with hypothetical life cycles. We model sexually antagonistic alleles in eight different sex determination systems and find that arguments 1 and 2 promote invasion and fixation of female-beneficial and male-beneficial alleles, respectively; argument 2 also improves prospects for polymorphism. Argument 3 harms the invasion prospects of sexually antagonistic alleles (irrespective of which sex benefits) but promotes fixation should invasion nevertheless occur. Disentangling the features helps to evaluate the validity of previous verbal arguments and yields better-informed predictions about intralocus sexual conflict under different sex determination systems, including hitherto undiscovered ones.
TL;DR: A model of host-mediated resource competition between mutualistic and pathogenic taxa in the gut that aims to explain why similar hosts, exposed to the same pathogen, can have such different infection outcomes is developed.
Abstract: The spread of an enteric pathogen in the human gut depends on many interacting factors, including pathogen exposure, diet, host gut environment, and host microbiota, but how these factors jointly influence infection outcomes remains poorly characterized Here we develop a model of host-mediated resource competition between mutualistic and pathogenic taxa in the gut that aims to explain why similar hosts, exposed to the same pathogen, can have such different infection outcomes Our model successfully reproduces several empirically observed phenomena related to transitions between healthy and infected states, including (1) the nonlinear relationship between pathogen inoculum size and infection persistence, (2) the elevated risk of chronic infection during or after treatment with broad-spectrum antibiotics, (3) the resolution of gut dysbiosis with fecal microbiota transplants, and (4) the potential protection from infection conferred by probiotics We then use the model to explore how host-mediated interventions-namely, shifts in the supply rates of electron donors (eg, dietary fiber) and respiratory electron acceptors (eg, oxygen)-can potentially be used to direct gut community assembly Our study demonstrates how resource competition and ecological feedbacks between the host and the gut microbiota can be critical determinants of human health outcomes We identify several testable model predictions ready for experimental validation
TL;DR: A definition of model systems from the biomolecular sciences is borrowed to assess how EEID researchers are (and are not) using 10 key model systems and concludes that model systems in EEID are not being used to their fullest and, in fact, cannot even be considered model systems.
Abstract: Ever since biologists began studying the ecology and evolution of infectious diseases (EEID), laboratory-based model systems have been important for developing and testing theory. Yet what EEID researchers mean by the term "model systems" and what they want from them is unclear. This uncertainty hinders our ability to maximally exploit these systems, identify knowledge gaps, and establish effective new model systems. Here, we borrow a definition of model systems from the biomolecular sciences to assess how EEID researchers are (and are not) using 10 key model systems. According to this definition, model systems in EEID are not being used to their fullest and, in fact, cannot even be considered model systems. Research using these systems consistently addresses only two of the three fundamental processes that underlie disease dynamics-transmission and disease, but not recovery. Furthermore, studies tend to focus on only a few scales of biological organization that matter for disease ecology and evolution. Moreover, the field lacks an infrastructure to perform comparative analyses. We aim to begin a discussion of what we want from model systems, which would further progress toward a thorough, holistic understanding of EEID.
TL;DR: Evidence of weak hybrid inviability between host-associated lineages of B. treatae is found despite strong genomic differentiation, and averaging across environments masked great variation in hybrid fitness on individual trees, where hybrids performed worse than, equal to, or better than residents.
Abstract: The role of divergent selection between alternative environments in promoting reproductive isolation (RI) between lineages is well recognized. However, most studies view each divergent environment as homogenous, thereby overlooking the potential role within-environment variation plays in RI between differentiating lineages. Here, we test the importance of microenvironmental variation in RI by using individual trees of two host plants, each harboring locally adapted populations of the cynipid wasp Belonocnema treatae. We compared the fitness surrogate (survival) of offspring from hybrid crosses with resident crosses across individual trees on each of two primary host plants, Quercus virginiana and Q. geminata. We found evidence of weak hybrid inviability between host-associated lineages of B. treatae despite strong genomic differentiation. However, averaging across environments masked great variation in hybrid fitness on individual trees, where hybrids performed worse than, equal to, or better than residents. Thus, considering the environmental context of hybridization is critical to improving the predictability of divergence under variable selection.