American Naturalist最新文献

AbstractAs environmental change accelerates globally, understanding concurrent organismal, species, and community responses is increasingly vital. Here, we examine these collective responses by incorporating genotype-specific thermal reaction norms into an eco-evolutionary predator-prey model, allowing us to track simultaneous phenotypic, ecological, and evolutionary responses to environmental change within ecological communities. We show that the reaction norms expressed by genotypes within a population determine how a community switches between different eco-evolutionary outcomes with changes in temperature. We identify how different components of phenotypic variation in thermal reaction norms-environmental (E), additive environmental and genetic ($E+G$), and gene-by-environment interactions ($G\times E$)-influence eco-evolutionary dynamics and outcomes as temperature changes. Our findings underscore how complex eco-evolutionary responses to environmental change ultimately emerge from variation in reaction norms among genotypes, offering new mechanistic insights into environmental impacts on adaptation, the maintenance of phenotypic and genetic variation, and ecological stability, which is crucial for understanding and predicting eco-evolutionary effects of rapid environmental change in the future.

AbstractThe extent of contemporary evolution, which is mediated by interactions with plasticity, will be an important determinant of biological responses to climate change. We synthesize two functional resurvey projects that, coupled with mechanistic models, evaluate the interplay of plasticity and evolution of pierid butterfly larval (thermal sensitivity of feeding) and adult (wing melanization) traits over recent decades. We characterize thermal environments over the resurvey periods, which we interface with developmental and (historical, current, and hypothetical) thermal sensitivity traits to examine the implications of evolutionary changes. We find that the evolution of photoperiod-cued plasticity of wing melanization in California Colias is consistent with avoiding thermal stress during warming springs. Plasticity has not evolved for Colorado Colias populations, which have experienced stronger increases in climate means relative to extremes in recent decades. Evolution in Colorado Colias larvae has improved tolerance to warm extremes, whereas evolution in California Colias larvae has broadened thermal sensitivity, consistent with capitalizing on expanded seasonal thermal opportunity. Our models predict that Washington Pieris larvae have experienced shifts in the direction of selection to increase performance at warm temperatures. The research highlights the importance of evaluating changes in climate change exposure and sensitivity to understand interacting organismal responses.

AbstractAbrupt ecosystem shifts during the Late Quaternary coincided with major climatic changes and intensified human activities, but the precise causes of these shifts remain debated. Here, building on previous hypotheses and work, we propose a new hypothesis that both plant beneficial and antagonistic soil microorganisms were the proximate drivers of Late Quaternary change. We synthesized evidence from paleoecological studies and contemporary ecosystems to understand how microbes and their interactions with plants shift ecosystem function. Because relevant paleoecological data are nonexistent, we reanalyzed a contemporary survey from grasslands and woodlands across Europe to test the general role of microbial diversity versus climate in controlling ecosystem function. Our models found that the richness of different microbial groups, including Proteobacteria, mycorrhizas, and plant fungal pathogens, were more strongly associated with the magnitude of direct effects on net primary productivity than temperature and precipitation. The richness of most of these groups was also influenced by climate, supporting our hypothesis that climate change may have indirectly caused past ecosystem shifts by changing microbial composition and function. We end by highlighting the potential of environmental DNA to reconstruct the biota and conditions of past ecosystems. Ultimately, improving our understanding of how microbes drove past ecosystem shifts may improve our ability to respond to future environmental changes.

AbstractAdaptive evolution is a key means for populations to persist under environmental change, yet whether populations across a species' range can adapt quickly enough to keep pace with climate change remains unknown. The breeder's equation predicts the evolutionary change in a trait from one generation to the next as the product of the selection differential and the narrow-sense heritability in that trait. Incorporating these aspects of the breeder's equation, we performed a resurrection study with the scarlet monkeyflower (Mimulus cardinalis) to evaluate whether traits associated with drought adaptation have evolved in populations across a species' range in response to extreme drought. We compared trait and fitness differences of predrought ancestors and postdrought descendants from six populations transplanted into three latitudinally arrayed common gardens and quantified phenotypic selection and trait heritabilities. The strength, direction, and mode of selection varied among traits and gardens. Trait heritabilities were relatively low and did not differ dramatically among populations or gardens. Overall, instances of evolutionary responses between ancestors and descendants were few and small in magnitude, but the magnitude of these evolutionary differences varied among gardens. These results suggest that evolutionary responses to climate change vary among populations in unpredictable ways and that the expression of these responses depend on environmental conditions, hindering our ability to predict evolutionary rescue under changing climate.

AbstractAfter a fitful start, the conceptual study of mutualism (mutually beneficial interspecific interactions) is now flourishing. In 1994, I reviewed the status of the field as reflected in the peer-reviewed literature; I also laid out directions for future research. Here, I look back on that assessment and offer an updated perspective on our understanding of mutualism. Most of the open questions I identified now have significant literatures of their own. New questions have sprung from each of these, and methodological innovations have made it more possible than ever before to obtain answers. I identify one astonishing gap from 1994: the absence of attention, either in journals or in my own synthesis, to the fate of mutualisms in a changing world. I offer a brief assessment of the now-massive literature on this topic. Finally, I suggest some directions in which the field as a whole might profitably move in the future.

AbstractAge influences behavior, survival, and reproduction; hence, variation in population age structure can affect population-level processes. The extent of spatial age structure may be important in driving spatially variable demography, particularly when space use is linked to reproduction, yet it is not well understood. We use long-term data from a wild bird population to quantify covariance between territory quality and age and examine spatial age structure. We find associations between age and aspects of territory quality, but little evidence for spatial age structure compared with the spatial structure of territory quality and reproductive output. We also report little between-year repeatability of spatial age structure compared with structure in reproductive output. We suggest that high breeding site fidelity among individuals that survive between years, yet frequent territory turnover driven by high mortality and immigration rates, limits the association between age and territory quality and weakens overall spatial age structure. Greater spatial structure and repeatability in reproductive output compared with age suggests that habitat quality may be more important in driving spatially variable demography than age in this system. We suggest that the framework developed here can be used in other taxa to assess spatial age structure, particularly in longer-lived species, where we predict from our findings there may be greater structure.

AbstractPollinators are important drivers of floral variation and speciation in plants. Here we investigate the effects of functional trait matching on pollen receipt in two plant species, Tritoniopsis revoluta and Nerine humilis, each visited by long-proboscid nemestrinid flies and bees across their ranges. Using single visits by pollinators to flowers with increased variance in floral morphology, we construct performance surfaces based on pollen receipt. We find divergent pollen receipt surfaces mediated by functionally different pollinators, within and between plant populations. Our results illuminate the nuances of how plants adapt to increase reproductive output in multipollinator communities, in which pollinators vary in their effectiveness.

AbstractThe population-level consequences of predator-prey interactions include unstable equilibria and predator-prey cycles with an approximate quarter-period phase lag. Prior studies have found that inducible defenses and rapidly evolving defenses alter the stability and phase lags of predator-prey systems differently: inducible defenses are stabilizing and decrease phase lags more frequently than evolving defenses. Using predator-prey models, we show that inducible and evolving defenses have the same range of possible effects, but the effects of inducible defenses depend on induction stimuli, reversibility, and timing. Inducible defenses responding to predator density, predator and prey densities, or predation cues are often stabilizing, but they can be destabilizing when defense is overexpressed. Only inducible defenses responding to predator and prey densities or the fitness gradient can increase phase lags. Compared with intragenerational reversible defenses, irreversible and transgenerational inducible defenses are less stabilizing and increase lags more when defense costs are sufficiently high; the opposite holds for low defense costs. We predict that inducible defenses are destabilizing and increase phase lags less often than evolving defenses because induction is a negative feedback (a self-limiting effect), whereas disruptive selection on an evolving defense is a positive feedback (a self-amplifying effect).

AbstractHeterogeneity and seeming unpredictability in responses to environmental change is driving a push to understand the underlying organismal mechanisms. The 2024 Vice Presidential Symposium of the American Society of Naturalists aimed to catalyze a promising and underutilized approach to extend understanding: repeating historical experiments or otherwise quantifying organism function through time. Many physiological, behavioral, ecological, and evolutionary experiments or observations reported in journal articles and elsewhere offer the potential for repeating the data collection to detect responses to environmental change. The approach extends beyond resurrection studies, which revive organisms to compare function and performance of modern organisms to their historical counterparts but are severely taxonomically and logistically restricted. In this introductory article, we discuss the promise of functional resurveys and highlight exemplar research repeating physiological measurements, behavioral experiments or observations, selection and quantitative genetic experiments, and measurement of ecosystem function. We also feature novel approaches to infer function from both modern and historical specimens and data, including temporal genomics, quantifying composition or energy stores, and genomic reconstruction. The research reveals key organismal mechanisms that mediate responses to environmental changes and can be accounted for to improve ecological and evolutionary forecasts.

AbstractIn organisms with separate sexes, the expected evolutionary change in a trait due to selection can be expressed using sex-specific Robertson covariances (RCs), that is, the additive genetic covariance between the trait and female relative fitness and the additive genetic covariance between the trait and male relative fitness. Sex-specific RCs capture the effects of (1) direct and indirect selection acting on the trait in the sex it is measured in ("within-sex selection") and (2) direct and indirect selection experienced by the underlying loci when expressed in the opposite sex ("cross-sex selection"). Using hemiclonal analysis in Drosophila melanogaster, we investigated the expected response to within-sex and cross-sex selection for a suite of traits involved in interlocus sexual conflict (IeSC) at male-biased, equal, and female-biased adult sex ratios. Our results are consistent with the idea that IeSC and sexual selection become stronger with the degree of male bias in adult sex ratio. The expected responses to cross-sex selection were small and typically concordant relative to the expected response to within-sex selection, with no evidence of intralocus sexual conflict for the traits we investigated. On the contrary, our findings imply that cross-sex selection may substantially boost the rate of adaptation in females.