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American Naturalist

Max Schmid, Ramon Dallo, Frédéric Guillaume
While clines in environmental tolerance and phenotypic plasticity along a single species' range have been reported repeatedly and are of special interest in the context of adaptation to environmental changes, we know little about their evolution. Recent empirical findings in ectotherms suggest that processes underlying dynamic species' ranges can give rise to spatial differences in environmental tolerance and phenotypic plasticity within species. We used individual-based simulations to investigate how plasticity and tolerance evolve in the course of three scenarios of species' range shifts and range expansions on environmental gradients...
June 2019: American Naturalist
Yvonne Willi, Josh Van Buskirk
Factors that limit the geographic distribution of species are broadly important in ecology and evolutionary biology, and understanding distribution limits is imperative for predicting how species will respond to environmental change. Good data indicate that factors such as dispersal limitation, small effective population size, and isolation are sometimes important. But empirical research highlights no single factor that explains the ubiquity of distribution limits. In this article, we outline a guide to tackling distribution limits that integrates established causes, such as dispersal limitation and spatial environmental heterogeneity, with understudied causes, such as mutational load and genetic or developmental integration of traits limiting niche expansion...
June 2019: American Naturalist
Jesús N Pinto-Ledezma, Alex E Jahn, Victor R Cueto, José Alexandre F Diniz-Filho, Fabricio Villalobos
No abstract text is available yet for this article.
June 2019: American Naturalist
Raymond B Huey, Theodore Garland, Michael Turelli
The comparative method has long been a fundamental exploratory tool in evolutionary biology, but this venerable approach was revolutionized in 1985, when Felsenstein published "Phylogenies and the Comparative Method" in The American Naturalist . This article forced comparative biologists to start thinking phylogenetically when conducting statistical analyses of correlated trait evolution rather than simply applying conventional statistical methods that ignore evolutionary relationships. It did so by introducing a novel analytical method (phylogenetically "independent contrasts") that required a phylogenetic topology with branch lengths and that assumed a Brownian motion model of trait evolution...
June 2019: American Naturalist
John W Benning, Vincent M Eckhart, Monica A Geber, David A Moeller
Species' geographic distributions have already shifted during the Anthropocene. However, we often do not know what aspects of the environment drive range dynamics, much less which traits mediate organisms' responses to these environmental gradients. Most studies focus on possible climatic limits to species' distributions and have ignored the role of biotic interactions, despite theoretical support for their importance in setting distributional limits. We used field experiments and simulations to estimate contributions of mammalian herbivory to a range boundary in the Californian annual plant Clarkia xantiana ssp...
June 2019: American Naturalist
Peter A Abrams
This article argues that adaptive evolutionary change in a consumer species should frequently decrease (and maladaptive change should increase) population size, producing adaptive decline. This conclusion is based on analysis of multiple consumer-resource models that examine evolutionary change in consumer traits affecting the universal ecological parameters of attack rate, conversion efficiency, and mortality. Two scenarios are investigated. In one, evolutionary equilibrium is initially maintained by opposing effects on the attack rate and other growth rate parameters; the environment or trait is perturbed, and the trait then evolves to a new (or back to a previous) equilibrium...
June 2019: American Naturalist
Sahas Barve, Walter D Koenig, Joseph Haydock, Eric L Walters
Joint nesting by females and cooperative polyandry-cooperatively breeding groups with a male-biased breeder sex ratio-are little-understood, rare breeding systems. We tested alternative hypotheses of factors potentially driving these phenomena in a population of joint-nesting acorn woodpeckers ( Melanerpes formicivorus ). During periods of high population density and thus low independent breeding opportunities, acorn woodpecker females formed joint-nesting coalitions with close kin. Coalitions were typically associated with groups with a male bias...
June 2019: American Naturalist
Maren N Vitousek, Michele A Johnson, Cynthia J Downs, Eliot T Miller, Lynn B Martin, Clinton D Francis, Jeremy W Donald, Matthew J Fuxjager, Wolfgang Goymann, Michaela Hau, Jerry F Husak, Bonnie K Kircher, Rosemary Knapp, Laura A Schoenle, Tony D Williams
Glucocorticoid (GC) hormones are important phenotypic mediators across vertebrates, but their circulating concentrations can vary markedly. Here we investigate macroevolutionary patterning in GC levels across tetrapods by testing seven specific hypotheses about GC variation and evaluating whether the supported hypotheses reveal consistent patterns in GC evolution. If selection generally favors the "supportive" role of GCs in responding effectively to challenges, then baseline and/or stress-induced GCs may be higher in challenging contexts...
June 2019: American Naturalist
Chris Duncan, David Gaynor, Tim Clutton-Brock, Mark Dyble
Kin selection theory suggests that altruistic behaviors can increase the fitness of altruists when recipients are genetic relatives. Although selection can favor the ability of organisms to preferentially cooperate with close kin, indiscriminately helping all group mates may yield comparable fitness returns if relatedness within groups is very high. Here, we show that meerkats ( Suricata suricatta ) are largely indiscriminate altruists who do not alter the amount of help provided to pups or group mates in response to their relatedness to them...
June 2019: American Naturalist
David M Zonana, Jennifer M Gee, Eli S Bridge, Michael D Breed, Daniel F Doak
Behavior can strongly influence rates and patterns of hybridization between animal populations and species. Yet few studies have examined reproductive behaviors in natural hybrid zones within the fine-scale social context in which they naturally occur. We use radio-frequency identification tags with social network analyses to test whether phenotypic similarity in plumage and mass correlate with social behavior throughout a breeding season in a California and Gambel's quail hybrid zone. We use a novel approach to partition phenotypic variation in a way that does not confound differences between sexes and species, and we illustrate the complex ways that phenotype and behavior structure the social environment, mating opportunities, and male-male associations...
June 2019: American Naturalist
Elena Dalla Benetta, Leo W Beukeboom, Louis van de Zande
Day length (photoperiod) and temperature oscillate daily and seasonally and are important cues for season-dependent behavior. Larval diapause of the parasitoid Nasonia vitripennis is maternally induced following a certain number of days (switch point) of a given critical photoperiod (CPP). Both the switch point and the CPP follow a latitudinal cline in European N. vitripennis populations. We previously showed that allelic frequencies of the clock gene period correlate with this diapause induction cline. Here we report that circadian expression of four clock genes- period ( per ), cryptochrome-2 ( cry-2 ), clock ( clk ), and cycle ( cyc )-oscillates as a function of photoperiod and latitude of origin in wasps from populations from the extremes of the cline...
June 2019: American Naturalist
Juliano Morimoto, Mathieu Lihoreau
Animals make feeding decisions to simultaneously maximize fitness traits that often require different nutrients. Recent quantitative methods have been developed to characterize these nutritional trade-offs from performance landscapes on which traits are mapped on a nutrient space defined by two nutrients. This limitation constrains the broad applications of previous methods to more complex data, and a generalized framework is needed. Here, we build on previous methods and introduce a generalized vector-based approach-the vector of position approach-to study nutritional trade-offs in complex multidimensional spaces...
June 2019: American Naturalist
Lauren L Truitt, Scott H McArt, Andrew H Vaughn, Stephen P Ellner
Epidemiological models for multihost pathogen systems often classify individuals taxonomically and use species-specific parameter values, but in species-rich communities that approach may require intractably many parameters. Trait-based epidemiological models offer a potential solution but have not accounted for within-species trait variation or between-species trait overlap. Here we propose and study trait-based models with host and vector communities represented as trait distributions without regard to species identity...
June 2019: American Naturalist
Philip H Crowley, Pete C Trimmer, Orr Spiegel, Sean M Ehlman, William S Cuello, Andrew Sih
Decisions made while searching for settlement sites (e.g., nesting, oviposition) often have major fitness implications. Despite numerous case studies, we lack theory to explain why some species are thriving while others are making poor habitat choices after environmental change. We develop a model to predict (1) which kinds of environmental change have larger, negative effects on fitness, (2) how evolutionary history affects susceptibility to environmental change, and (3) how much lost fitness can be recovered via readjustment after environmental change...
May 2019: American Naturalist
Pacifica Sommers, Peter Chesson
Predator avoidance behavior, in which prey limit foraging activities in the presence of predation threats, affects the dynamics of many ecological communities. Despite the growing theoretical appreciation of the role predation plays in coexistence, predator avoidance behavior has yet to be incorporated into the theory in a general way. We introduce adaptive avoidance behavior to a consumer-resource model with three trophic levels to ask whether the ability of prey-the middle trophic level-to avoid predators alters their ability to coexist...
May 2019: American Naturalist
Jussi Lehtonen, Geoff A Parker
Transition from isogamy to anisogamy, hence males and females, leads to sexual selection, sexual conflict, sexual dimorphism, and sex roles. Gamete dynamics theory links biophysics of gamete limitation, gamete competition, and resource requirements for zygote survival and assumes broadcast spawning. It makes testable predictions, but most comparative tests use volvocine algae, which feature internal fertilization. We broaden this theory by comparing broadcast-spawning predictions with two plausible internal-fertilization scenarios: gamete casting/brooding (one mating type retains gametes internally, the other broadcasts them) and packet casting/brooding (one type retains gametes internally, the other broadcasts packets containing gametes, which are released for fertilization)...
May 2019: American Naturalist
Jedediah F Brodie, William D Newmark
A fundamental tenet of modern ecology and conservation science is the fact that species occurrence in habitat patches can be determined by patch area and isolation. But such island biogeographic models often poorly predict actual species occurrences in structurally complex landscapes that typify most ecosystems. Recent advances in circuit theory have enhanced estimates of species dispersal and can provide powerful ways to predict landscape-scale distribution of species assemblages through integration with island biogeography...
May 2019: American Naturalist
Lea M Callan, Frank A La Sorte, Thomas E Martin, Vanya G Rohwer
High predation risk can favor rapid offspring development at the expense of offspring quality. Impacts of rapid development on phenotypic quality should be most readily expressed in traits that minimize fitness costs. We hypothesize that ephemeral traits that are replaced or repaired after a short period of life might express trade-offs in quality as a result of rapid development more strongly than traits used throughout life. We explored this idea for plumage quality in nestling body feathers, an ephemeral trait...
May 2019: American Naturalist
Devin Kirk, Pepijn Luijckx, Andrijana Stanic, Martin Krkošek
The metabolic theory of ecology (MTE) provides a general framework of allometric and thermal dependence that may be useful for predicting how climate change will affect disease spread. Using Daphnia magna and a microsporidian gut parasite, we conducted two experiments across a wide thermal range and fitted transmission models that utilize MTE submodels for transmission parameters. We decomposed transmission into contact rate and probability of infection and further decomposed probability of infection into a product of gut residence time (GRT) and per-parasite infection rate of gut cells...
May 2019: American Naturalist
Hanna Ten Brink, André M de Roos, Ulf Dieckmann
Almost all animal species undergo metamorphosis, even though empirical data show that this life-history strategy evolved only a few times. Why is metamorphosis so widespread, and why has it evolved? Here we study the evolution of metamorphosis by using a fully size-structured population model in conjunction with the adaptive-dynamics approach. We assume that individuals compete for two food sources; one of these, the primary food source, is available to individuals of all sizes. The secondary food source is available only to large individuals...
May 2019: American Naturalist
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