American Naturalist最新文献

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.

AbstractMost species distributions are dynamic, and as species distributions change they often encounter novel environments and resident species. To establish new populations, ecologically similar species compete with residents for resources while adapting to the environment. Yet local adaptation in residents can allow them to outcompete maladapted invaders and prevent their establishment. Indeed, local adaptation often improves male condition but also intensifies sexual conflict, a process where males increase their fitness while decreasing female fitness. Using an eco-evolutionary model, we show that sexual conflict can prevent adapted residents from monopolizing resources. This cost of adaptation in the residents opens a window of opportunity for the establishment of maladapted invaders. Female resistance to male harm can, however, prevent the invader from establishing. Sexual conflict can therefore reduce differences in competitive ability, facilitating establishment, but does not affect niche differences. However, when sexual conflict is density dependent, it can facilitate resident and invader coexistence, even when interspecific competition is stronger than intraspecific competition. Our results show that reproductive interactions may critically shape the dynamics of species invasions and species coexistence.

AbstractSeveral metrics have been proposed to measure phenotypic parallel evolution. All of these metrics stem from a geometric definition of parallel evolution in which two evolutionary trajectories are, literally, parallel or nonparallel to each other. Two metrics fit this definition: the interaction term between population and habitat in a two-factor ANOVA and a measure of the angle between two multivariate trajectories of evolution. A third metric is derived from the general direction of multivariate trajectories; although this might fit our intuition about parallel evolution, it does not fit the geometric definition. A fourth metric is based on the amount of variation explained by the habitat variable in a one-factor ANOVA (i.e., the R²). We show here that the R² metric does not reliably measure any aspect of parallelism and should be avoided. We also discuss the importance of establishing proper ancestor-descendent relationships in attempting to use any of the valid metrics to quantify parallel evolution. Finally, because different metrics measure different aspects of evolutionary trajectories, we recommend being explicit about what one is trying to measure (angle, direction, or length of trajectories).

AbstractMultitrait analyses can be used to measure the differential performance of phenotypic traits in species complexes. Hybridization within these complexes can result in a mismatch between mitochondrial and nuclear DNA that may lead to reduced performance and acclimation capacity in hybrids. To test the effect of this mismatch on physiology, we compared physiological performance and acclimation capacity of metabolic rate ($\dot{\mathrm{V̇}}{\mathrm{CO}}_2$) and total resistance to water loss (r_T) between two sexual Ambystoma species and a closely related unisexual lineage. We also separated unisexuals by their unique biotypes to determine how physiology varies with subgenomic composition. We found that unisexual biotypes exhibited phenotypes more like their related sexual species than other unisexuals. We also found a trade-off between r_T and $\dot{\mathrm{V̇}}{\mathrm{CO}}_2$, with increasing r_T resulting in a decrease in $\dot{\mathrm{V̇}}{\mathrm{CO}}_2$. Although we did not find evidence for mitonuclear mismatch, our results indicate that the genomic composition of hybrids may be a suitable predictor of hybrid trait performance. Multitrait analyses are imperative for understanding variation in phenotypic diversity, providing insight into how this diversity affects species responses to environmental change.

AbstractSynthetic gene drives are being investigated as tools to suppress pest populations, and it is important to understand how natural selection will act on variant drivers that may either arise by de novo mutation or be intentionally released. In this study, we extend previous spatially implicit stochastic models to examine the evolutionary dynamics of synthetic driving Y chromosomes in patchy environments when population size is responding dynamically to the spread of the driver and derive conditions for the existence of an evolutionarily stable strategy (ESS) for drive strength. Under broad conditions, an intermediate drive strength emerges as the ESS, capable of outcompeting both stronger and weaker variants. Additionally, we show how the intentional release of two drivers straddling the ESS can help stabilize population dynamics. Finally, inbreeding depression has the effect of expanding the range of conditions under which no intermediate ESS exists, with ever stronger drive being selected until the population is eliminated. These results provide insights into the expected evolutionary trajectories of gene drive systems, with important implications for the design and release of gene drives for pest and vector control.