Exploring the timing of life-history transitions has been a pivotal focus in the field of evolutionary ecology. Studies on amphibian metamorphosis are well suited to investigate this aspect. We ...propose a species-specific model to predict the optimal metamorphosis point for frog individuals with different larval growth trajectories. Because overall fitness will be determined throughout both aquatic and terrestrial stages, we included growth and survival rates of aquatic and terrestrial stages in the fitness equation. Then we conducted a rearing experiment on a brown frog, Rana ornativentris, as an example to obtain the size at metamorphosis, larval period, and larval growth trajectory. Based on these results, we determined the model's parameters to fit the actual metamorphosis patterns. Because the parameters are supposed to be evolutionarily maintained, our data-driven approach enabled obtaining fundamental ecological information (evolutionally-based life-history parameters) of the target species. Comparing the parameters among species will allow us to understand the mechanisms in determining life-history transition more deeply.
Fleshy fruits can be divided between climacteric (CL, showing a typical rise in respiration and ethylene production with ripening after harvest) and non-climacteric (NC, showing no rise). However, ...despite the importance of the CL/NC traits in horticulture and the fruit industry, the evolutionary significance of the distinction remains untested. In this study, we tested the hypothesis that NC fruits, which ripen only on the plant, are adapted to tree dispersers (feeding in the tree), and CL fruits, which ripen after falling from the plant, are adapted to ground dispersers. A literature review of 276 reports of 80 edible fruits found a strong correlation between CL/NC traits and the type of seed disperser: fruits dispersed by tree dispersers are more likely to be NC, and those dispersed by ground dispersers are more likely to be CL. NC fruits are more likely to have red–black skin and smaller seeds (preferred by birds), and CL fruits to have green–brownish skin and larger seeds (preferred by large mammals). These results suggest that the CL/NC traits have an important but overlooked seed dispersal function, and CL fruits may have an adaptive advantage in reducing ineffective frugivory by tree dispersers by falling before ripening.
Studying the interaction between evolutionary and ecological processes (i.e. eco-evolutionary dynamics) has great potential to improve our understanding of biological processes such as species ...interactions, community assembly and ecosystem functions. However, most experimental studies have been conducted under controlled laboratory or mesocosm conditions, and the importance of these interactions in natural field communities has not been evaluated. In this study, we focused on the contemporary divergence of a competitive trait (the height–width ratio) of an annual grass
Eleusine indica
between urban and farmland populations and investigated how trait evolution affects ecological processes by transplanting
E. indica
individuals from lineages with different trait values into semi-natural grassland. The competitive trait of the transplanted individuals not only affected their own growth and fitness, but also affected the vegetative growth of the competing species and the species diversity. These results indicate that the evolution of competitive traits, even in a single species, can influence the community species diversity through changes in interspecific interactions. Eco-evolutionary interactions therefore play a crucial role in natural field environments. Our results suggest that understanding intraspecific variation in competitive traits driven by rapid evolution is essential for understanding interspecific competitive interactions, community assembly and species diversity.
The role of competition in local adaptation and the associated traits underlying adaptation remain unclear. One reason for the lack of evidence may be that plant-plant competition is ubiquitous in ...natural environments; thus, local adaptation to different levels of competition is difficult to test. Comparison between urban and rural habitats is suitable for examining the evolutionary impacts of competition because these habitats share several plant species, but differ greatly in plant density and their resulting degree of competition. Here, using methods of landscape ecology, we propose a landscape evolutionary ecological approach—a simple analytical framework—to investigate how landscape changes in urban–rural gradients drive the local adaptation of competitive traits. We demonstrated adaptive divergence of competitive traits (i.e. growth habits) between urban and rural populations in two Poaceae plants (
Digitaria ciliaris
and
Eleusine indica
) and summarised the experimental procedure to examine local adaptation to different levels of competitive environments. Landscape change due to urbanisation provides an opportunity to understand the drivers and constraints of the evolution of plant competitive traits. Our analytical framework will be useful for integrating research on urban evolution conducted in different countries and regions.
Competition among neighbouring plants plays essential roles in growth, reproduction, population dynamics, and community assembly, but how competition drives local adaptation and the traits underlying ...the adaptation remain unclear. Here, we focused on populations of the aggressive weed Digitaria ciliaris from urban and rural habitats as low‐ and high‐competition environments for light resources and examined how competitive interaction drove contemporary adaptive divergence of competitive traits.
To examine local adaptation to different competitive environments in D. ciliaris and the specific traits that have been selected for, we compared growth rate and competitive traits in plants from farmland and urban populations between high‐ and low‐competition treatments. Furthermore, we conducted a field tillage experiment with drone (unmanned aerial vehicle) monitoring to examine the possibility that trait evolution in farmland habitats might influence weed management practices in crop fields.
Plants from farmland populations had higher growth rates than plants from urban populations in high‐competition treatments, and vice versa in low‐competition treatments. Among populations, those with larger height/width ratios (farmland populations) were more tolerant of above‐ground competition in high‐competition treatments, but among individuals, those with larger ratios had lower growth rates in low‐competition treatments. More plants from farmland populations, which had thicker stems (and larger height/width ratios), survived after experimental tillage than plants from urban habitats with thinner stems.
Synthesis. Our study empirically demonstrated adaptive divergence in competitive traits in above‐ground competitors and its underlying traits. Moreover, contemporary adaptive divergence between urban and rural plant populations has practical implications for weed control. The urban–rural model system can thus contribute to both basic and applied research in plant evolutionary ecology. Further research is required to understand adaptive divergence in plants between urban and rural environments, and the traits underlying the adaptation, not only above‐ground but also below‐ground.
To understand how competition drives local adaptation and trait change, we focused on urban and rural habitats as low‐ and high‐competition environments. We showed that farmland of Digitaria ciliaris, had greater height/width ratios with thicker stems and higher growth rates than urban genotypes in high‐competition treatments, and vice versa in low‐competition treatments. Furthermore, the farmland genotypes with thicker stems were more likely to survive following mechanical tillage.
AbstractCompetitive interaction among individuals of a single population may result in the differentiation of two or more distinct life-history tactics. For example, although they exhibit unimodal ...size distribution, male juveniles of salmonids differentiate into those going down to the ocean to grow and returning to the natal stream after several years to reproduce (migratory tactic) and those staying in the stream and reproducing for multiple years (resident tactic). In this study, we developed a simple mathematical model for the positive feedback between hormonal and behavioral dynamics, with the expectation of establishing multiple discrete clusters of hormone levels leading to differentiation of life-history tactics. The assumptions were that probability of winning in fighting depends both on the body size and hormone level of the two contestants. An individual with a higher hormone level would be more likely to win the competition, which further enhanced hormone production, forming a positive feedback loop between hormone level and fighting ability. If the positive feedback was strong but not excessive, discrete clusters of hormone levels emerged from a continuous distribution. In contrast, no clear clustering structure appeared in the distribution of hormone levels if the probability of winning in fighting was controlled by the body size.
Status-dependent strategies represent one of the most remarkable adaptive phenotypic plasticities. A threshold value for individual status (e.g., body size) is assumed above and below which each ...individual should adopt alternative tactics to attain higher fitness. This implicitly assumes the existence of an “absolute” best threshold value, so each individual chooses a tactic only on the basis of its own status. However, animals may be able to assess their status on the basis of surrounding individuals. This “relative” assessment considers a threshold value to be changeable depending on individual situations, which may result in significant differences in ecological and evolutionary dynamics compared with absolute assessment. Here, we incorporated Bayesian decision-making and adaptive dynamics frameworks to explore the conditions necessary for each type of assessment to evolve. Our model demonstrates that absolute assessment is always an evolutionarily stable strategy (ESS) in a stable environment, whereas relative assessment can be an ESS in stochastic environments. The consequences of future environmental change differ considerably depending on the assessment chosen. Our results underscore the need to better understand how individuals assess their own status when choosing alternative tactics.
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•Tragedy of the commons occur when plants compete for limited resources.•Growth dynamics and resource allocation was applied to belowground competition in plants.•We found ...evolutionarily stable resource allocation strategy in the presence of neighboring plant.•Root overproliferation did not always occur in the tragedy of the commons game.•Careful observation required for examining plant species in game theoretic situation.
The tragedy of the commons (TOC) has been well known since it was proposed and has been widely applied not only to human society but also to many taxa. An increasing number of studies have focused on TOC in belowground competition in plants. In the presence of neighbors, plants overproduce roots to acquire more nutrients than their competitors, resulting in a reduction in reproductive yield. Game-theoretic studies on TOC in plants usually consider the amount of root biomass as a strategy and do not consider the growth of plants. However, root volume is considered an outcome of the decision-making of plants on whether they allocate more resources to the root. In this study, we incorporated resource allocation and growth dynamics into the TOC game in plants and explored the evolutionarily stable resource allocation strategy in the presence of neighbors. We demonstrated that TOC generally occurs when fitness per individual is always reduced because of the competitive response. However, the overproliferation of roots, which is emphasized as an indicator of TOC, did not necessarily occur, or was sometimes difficult to detect when fitness is largely or completely determined by root biomass. This result suggests the importance of careful observation for examining whether plant species engage in a TOC game
The enhanced or reduced growth of juvenile masu salmon (
Oncorhynchus masou masou
) may result from climate changes to their environment and thus impact on the eco-evolutionary dynamics of their ...life-history choices. Male juveniles with status, i.e., if their body size is larger than a threshold, stay in the stream and become resident males reproducing for multiple years, while those with smaller status, i.e., their body size is below the threshold, migrate to the ocean and return to the stream one year later to reproduce only once. Since juvenile growth is suppressed by the density of resident males, the fraction of resident males may stay in equilibrium or fluctuate wildly over a 2-year period. When the threshold value evolves, the convergence stable strategy may generate either an equilibrium or large fluctuations of male residents. If environmental changes occur faster than the rate of evolutionary adaptation, the eco-evolutionary dynamics exhibit a qualitative shift in the population dynamics. We also investigated the relative assessment models, in which individual life-history choices are made based on the individual’s relative status within the juvenile population. The eco-evolutionary dynamics are very different from the absolute assessment model, demonstrating the importance of understanding the mechanisms of life history choices when predicting the impacts of climate change.
•In masu salmon, large male juveniles stay in streams; small ones migrate to ocean.•We studied population dynamics when juvenile growth is suppressed by residents.•Resident population may show ...equilibrium, cycle with many years, and chaos.•We examined the evolution of threshold by calculating selection gradient.•Evolutionary bistability exists; one with stable dynamics, and the other with cycle.
Within the salmonid species, some male juveniles after spawning in fresh water stream migrate to the ocean and return to their natal streams after maturation, while others stay and mature in the fresh water stream only. Migration is relative to the size of the individuals. This is an evolutionary outcome according to the status-dependent strategy model, which assumes that the juveniles exhibit the optimal tactic based on their status. In this paper, we consider the case in which the density of adult residents suppresses juvenile growth, and explore the dynamics of alternative tactics and the evolution of threshold size. We show that a fraction of the migratory tactic that might converge into a stable state or continue to fluctuate wildly, and that the evolutionary outcome might be evolutionarily bistable, resulting in a clearly different threshold size. In the case of evolutionary bistability, two threshold sizes differ in ecological dynamics either by stable fraction of migratory tactic or showing two-year periodic fluctuation.
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