American Naturalist最新文献

AbstractWarming induces metabolic changes in microbial organisms, including increased respiration. Empirical studies have shown that evolution can compensate for thermal sensitivity and reduce respiration rate at high temperatures. Evolutionary adaptation may mitigate the effects of warming, but it remains unclear to what extent organisms can overcome thermodynamic constraints through evolution. Furthermore, evolutionary adaptations are modulated by interactions with plastic changes to respiration and other metabolic traits. We develop a mechanistic model including both evolution and metabolic plasticity to explore how adaptation to temperature affects variability in metabolic traits in mixotrophic marine microorganisms under thermal stress. By combining modeling with empirical data, we show that variability in metabolic activity between mixotrophs with different temperature histories can be explained by changes to the carbon budget facilitated by evolved reductions in respiration. The model suggests that evolution enhances thermal resilience over evolutionary timescales. Evolving mixotrophs exhibit less metabolic variability in response to temperature changes. In contrast, over shorter timescales plastic responses dominate over evolutionary adaptations, producing transient changes to metabolic activity following a temperature change. These results highlight the interplay between different biological adaptive mechanisms and provide a modeling framework for representing variability in microbial metabolism in the context of climate change.

AbstractEcologists differ in the degree to which they consider the linear type I functional response to be an unrealistic versus sufficient representation of predator feeding rates. Empiricists tend to consider it unsuitably nonmechanistic, and theoreticians tend to consider it necessarily simple. Holling's original rectilinear type I response is dismissed by satisfying neither desire, with most compromising on the smoothly saturating type II response for which searching and handling are assumed to be mutually exclusive activities. We derive a "multiple-prey-at-a-time" response and a generalization that includes the type III to reflect predators that can continue to search when handling an arbitrary number of already-captured prey. The multiprey model clarifies the empirical relevance of the linear and rectilinear models and the conditions under which linearity can be a mechanistically reasoned description of predator feeding rates, even when handling times are long. We find evidence for the presence of linearity in 35% of 2,591 compiled empirical datasets and support for the hypothesis that larger predator-prey body mass ratios permit predators to search while handling greater numbers of prey. Incorporating the multiprey response into the Rosenzweig-MacArthur population dynamic model reveals that a nonexclusivity of searching and handling can lead to coexistence states and dynamics that are not anticipated by theory built on the linear type I, type II, and type III models. In particular, it can lead to bistable fixed point and limit cycle dynamics with long-term crawl-by transients between them under conditions where abundance ratios reflect top-heavy food webs and the functional response is linear despite having an inherent upper limit. We conclude that functional response linearity should not be considered empirically unrealistic but also that more cautious inferences should be drawn in theory presuming the linear type I to be appropriate.

AbstractWarming climate has led to significant phenological advances in many plant and animal populations. Whether these advances represent evolutionary responses or phenotypic plasticity remain typically unknown. Using a 53-year-long time series of individually marked Great Tits (Parus major) and Willow Tits (Poecile montanus), we investigated whether the significant breeding time advances in these species could be explained as resulting from evolutionary responses, phenotypic plasticity, or both. In the case of both species, we did not find any evidence for changes in breeding values for timing of breeding, suggesting that the observed changes do not have a genetic and, hence, evolutionary basis. In contrast, we found that annually fluctuating environmental effects explained most of the variation in first egg-laying dates, suggesting that advances in breeding time were attributable to phenotypic plasticity. We further inferred that phenotypic plasticity in response to spring temperatures can fully explain the observed advancement of Great Tit phenology over time, whereas Willow Tits have advanced their phenology much beyond what would be expected from phenotypic plasticity in response to spring temperatures. The latter observation suggests that some other yet unidentified environmental factor, uncorrelated with spring temperatures, likely explains about half of the advancement in their breeding time.

AbstractThe evolution of sexual dimorphism is predicted to resolve conflict that can arise from divergent evolutionary interests between sexes, enabling each sex to reach its fitness optimum. However, most of the genome is shared between sexes, which can lead to a genetic constraint for dimorphism evolution. Most studies of intersexual genetic constraints have focused on the effect of genetic correlations, r_mf, for single traits. However, multivariate studies of the B matrix of intersexual genetic covariances suggest that sexual dimorphism may be more evolvable than inferred from r_mf because of the potential for indirect responses to selection from correlated traits. To comprehensively address this question, we collected and reanalyzed published estimates of B using a recently developed approach to quantify the evolvability of sexual monomorphism and dimorphism. We find that across the traits and species we study, the evolvability of dimorphism is lower than that of monomorphism, but also that sexually concordant and antagonistic selection are almost equally capable of producing dimorphism. We also find that asymmetry in B would affect the response to selection more in females than in males. Our results show that sexual dimorphism is more evolvable than studies of r_mf suggest and underscore that sexually antagonistic selection is not required for the evolution of sexual dimorphism.

AbstractMetapopulations span environmental gradients and experience variable rates of environmental change, with populations differing in their tolerance and evolutionary capacity. Our study aimed to quantify the extent to which interactions between population-specific traits and spatial environmental heterogeneity affect metapopulation persistence under climate change. Using an eco-evolutionary model, we simulated 25 population types with varying thermal tolerance breadths and genetic variance, impacting the strength of selection and rate of evolutionary response, respectively. We applied this framework to marine ecosystems, which face significant threats from climate change, with many habitat-forming organisms such as coral, oysters, and kelp existing as metapopulations connected through propagule dispersal via ocean currents. We tracked the response of different populations under sea surface temperature spatial ranges and projected warming rates to 2100 that are specific to 49 large marine ecosystems. We found that the rate of warming was the strongest predictor of the number of persistent metapopulations, where faster warming reduced the population types that a region could support. We also found that cooler subpopulations outperformed warmer ones, likely due to immigration from warmer sites, suggesting that cooler sites may act as climate refugia.

AbstractElevational distributions have long fascinated scientists, an interest that has burgeoned with studies of predicted upslope range shifts under climate change. However, this body of work has yielded conflicting results, perhaps due to varied conceptual and statistical approaches. Here I explore how ecological processes and researcher decisions shape the patterns characterized by elevational ranges. I use community science data to illustrate (1) that elevational ranges include variation in abundance; (2) that elevational ranges are usually estimated, not observed directly; (3) that elevational ranges are dynamic across short distances and time intervals; and (4) that how we describe elevational ranges has consequences for inference of range shifts. I present a conceptual framework for understanding elevational ranges across multiple spatial scales and propose that elevational distributions are governed by scale-dependent processes. This framework implies that accurately quantifying elevational ranges and learning how they are formed or maintained requires matching questions to their appropriate scale domain. I provide a list of best practices for studying elevational ranges and highlight promising directions for future research into these complex phenomena.

AbstractUnderstanding and identifying factors influencing the likelihood of sudden transitions in ecological systems is a significant area of scientific research. Environmental fluctuations are particularly important, as they can trigger these transitions before reaching the system's condition to a deterministic tipping point. While there has been much focus on noise-induced tipping due to uncorrelated environmental noise, the impact of correlated noise on multispecies systems has been relatively overlooked. Specifically, studies have neglected the impact of correlations between species responses to environmental changes and a system's susceptibility to tipping. This study examines various two-species ecological models representing different interaction types in noisy environments. We reaffirm that elevated positive temporal autocorrelations in environmental fluctuations aggravate the chance of tipping. Conversely, our key findings suggest that elevated positive correlations in species responses generally delay the onset of tipping, except when the system dynamics is solely driven by positive interspecific interactions. The correlation of species responses is also critical in determining the reliability of early warning signals for predicting sudden ecological changes. Our findings highlight the importance of considering the similarity between species' responses to environmental variability, which significantly influences the likelihood and detectability of dramatic ecological transitions.

AbstractEvolution requires both robustness of adaptive states and transitions between them. Understanding the mechanisms that reconcile these seemingly opposing properties is limited by the transient nature of evolutionary processes, where past pathways and contexts are often lost. Here, we overcome this limitation by tracing the biochemical evolution of avian carotenoid networks on the global carotenoid biochemical network, which is unmodified in avian evolution. By mapping enzymatic interactomes of 260 extant bird species and their reconstructed ancestral states onto this global network, we reveal that stepping stones between them are evolutionarily stable degenerate carotenoids-compounds that can be synthesized interchangeably by different dietary carotenoid-specific pathways. We find that ecological specialization across taxonomic groups is consistently associated with an uneven biochemical reach of individual dietary carotenoids, leading to increased fragmentation and reduced resilience of enzymatic networks to failure. However, the robustness of enzymatic networks of specialized groups is restored by the accumulation of degenerate carotenoids. This accumulation enables direct transitions between ecological specializations and sustains evolutionary explorations. Thus, the same feature of network structure-its degeneracy-increases the robustness of specialized enzymatic networks as enables evolutionary transitions between them. These findings provide an insight into the mechanistic basis for the interplay between natural selection and historical contingency, highlighting their fundamental interdependence.

AbstractFamily groups, ranging from simple to complexly structured, are widespread in the animal kingdom, with parent-offspring interactions in the form of parental care traditionally considered the primary driver of family life. However, recent considerations suggest that sibling cooperation might have facilitated the early evolution of social and family life. While the effects of isolated family interactions have been extensively studied, the intricate dynamics between different family interactions and their reciprocal impacts have gained little attention. Using a full-factorial social isolation experiment in the subsocial burying beetle Nicrophorus vespilloides, where we isolated offspring from siblings and/or parents, we showed that offspring benefited from the presence of both parents as well as siblings. The positive effects of siblings were evident in the absence and presence of parents, although they manifested differently. Without parents, growing alongside siblings resulted in higher larval mass at dispersal, perhaps due to advantages of collective feeding. With parents, having siblings accelerated early growth and increased survival, possibly due to higher begging activity, which may have influenced parental investment. Our results support the notion that beneficial sibling interactions are an important part of facultative family systems and may encourage offspring to stay in a family group.

AbstractLaboratory measurements of physiological traits have long been used to infer the thermal limits and preferences of species in the field. However, it remains unclear how well individual physiological traits scale up to explain broad distribution patterns of species, such as their climatic limits, the breadth of temperatures they occur in, and the conditions at which population abundances are highest. We address these gaps by combining laboratory-measured thermal traits (critical thermal minimum [CT_min], critical thermal maximum [CT_max], and thermal preference [T_pref]) with occurrence and abundance data from 21 species of Anolis lizards collected from extensive mark-resight surveys of communities across the Caribbean islands of Puerto Rico and Hispaniola. Our findings suggest that thermal limits do map to distribution boundaries, such that CT_max and CT_min are significant predictors of maximum and minimum environmental temperatures at which species occur in nature, albeit with substantial error. Curiously though, physiological niche breadth (${\mathrm{CT}}_{\max }-{\mathrm{CT}}_{\min }$) does not positively correlate with climatic niche breadth. This means that species able to tolerate a wide range of temperatures do not always occur across a broad range of climates, limiting our ability to make clear-cut statements about what constitutes a thermal generalist or specialist. The climatological temperature where population abundance is maximized is the geographic feature best predicted by physiology, yet counterintuitively T_pref performs worse than critical thermal limits at predicting where this abundance peak occurs. Together, our findings suggest that individual physiological responses to temperature do not always translate to distribution patterns in predictable ways, suggesting a substantial role for other factors, such as competition, predation, nonthermal habitat characteristics, and behavioral buffering, in setting range-wide distribution patterns.