(Re)appreciating the role of life history in Eco-evolutionary dynamics?
Contents
Individual variation in life history and eco-evolutionary dynamics: Towards more flexible model frameworks and new applications
Movement as a central trait in life history
How do butterflies respond to environmental stress in natural populations and when are these responses adaptive
The roles of environmental context and life history in mediating ecological succession
Life-history trade-offs driving pathogen evolution and epidemiology
Life history and above-belowground interactions
Life-history traits and the properties of meta-ecosystems: a theoretical perspective
Individual variation in life history and eco-evolutionary dynamics: Towards more flexible model frameworks and new applications
Yngvild Vindenes
Individual variation in life histories can arise from a number of mechanisms, and is essential to our understanding of eco-evolutionary dynamics. Demographic frameworks such as matrix models and integral projection models represent powerful tools to investigate the joint dynamics of individual traits and population level parameters. However, most applications of such models assume that all individuals follow the same average life history, so that at a given age (or size) they will have the same vital rates (survival, growth and transition rates). While the average life history is a key characteristic of a species, recent studies have also emphasized the importance of variation in life histories to eco-evolutionary processes. I will present a flexible general demographic framework for investigating such processes, that distinguishes between two types of individual-level state variables: Static traits represent underlying individual properties that remain constant over the lifetime, such as genotype, whereas dynamic traits, such as age or body size, change over the lifetime. The static and dynamic traits can have different effects on vital rates (survival, fecundity, and transitions) and may also interact so that a genotype may give rise to different vital rate effects across the lifetime, for example. This framework allows a wide range of individual variation in life history to be modeled, as well as different types of inheritance. I present an empirical example for a population of pike (Esoxlucius), where large variation in life history arises through early-life differences in somatic growth. Using this model, we evaluate the consequences of ignoring such life history differences for important demographic outputs such as the mean and variance of the population growth rate, the net reproductive rate, and generation time. We also explore how projected responses to ongoing climate change (warming) and harvesting may depend on the individual life history differences.
Movement as a central trait in life history
Dries Bonte
Life histories have received a lot of attention in ecology as they are providing a template to understand adaptations towards habitat types that differ in their level of productivity and predictability. Especially the study of trade-offs among some major life historycomponents (age at maturity, lifespan and reproduction) allowed the development of a quantitative framework to understand how environmental variation shapes patterns of biodiversity. There is incremental evidence that evolutionary changes in life histories feedback on ecological processes at contemporary timescales. Insights on the importance and magnitude of these eco-evolutionary dynamics are typically derived from populations inhabiting homogeneous environments. The world is, however, spatially structured and individuals move within and among habitats to maximize fitness. Movement consequently needs to be considered asa central trait in life histories. I will use an optimality framework to demonstrate how this integration of movement might substantially change our view on evolutionary trajectories in spatially structured environments. Because changes in the spatial configuration of habitats affect the costs of movement and dispersal, adaptations to reduce these costs will increase phenotypic divergence among and within populations. This phenotypic heterogeneity leads to non-random dispersal and isanticipated to impact population and community dynamics. I will present empirical evidence on the central role of movement and dispersal on the spatial distribution of ecological strategies and its impact on population spread, invasions and coexistence.
How do butterflies respond to environmental stress in natural populations and when are these responses adaptive
Marjo Saastamoinen
Organisms in the wild are constantly faced with a wide range of environmental variability, such as fluctuation in thermal conditions or in food quality and quantity. Understanding the processes and the underlying mechanisms that allow organisms to cope with such environmental variation is one of the biggest challenges in ecology and evolutionary biology. My research focuses on the influence of environmental stress during different life stages on the subsequent life-history variation in the Glanville fritillary butterfly (Melitaeacinxia). Poor conditions during development or during adult stage often have a negative impact on fitness-related traits, such as reproduction and lifespan. However, in some cases individuals can use the experienced conditions as cues for the likely environmental condition the individual will encounter later on in life (i.e. predictive adaptive responses) or of their current state. Accordingly, individuals can shape their adult morphology, physiology or life history in a way that allows them to best deal with the current or the predicted conditions later on in life, or even to move away from these deteriorating environments.
The roles of environmental context and life history in mediating ecological succession
Matthew Bracken
A central goal of community ecology is to understand the processes that mediate the diversity of organisms in a location. Here, I explore how environmental context - including elevation, disturbance, herbivory, thermal stress, and nutrient availability - interacts with life history to determine successional trajectories, biodiversity, and resilience. I evaluated these processes by clearing 160 experimental plots on a rocky shoreline in California, USA. Plots were equally divided between two tidal elevations crossed with two wave exposures, and thermal stress (shaded, unshaded), herbivore access (present, excluded), and nutrient availability (added, ambient) treatments were factorially applied to plots. I monitored colonization and growth of seaweed species for 18 months to evaluate how environmental context and experimental manipulations affected seaweed succession and diversity. In particular, I focus on the emergence of nested patterns of species occurrence across realistic gradients in diversity and highlight how species life history traits interact with factors such as herbivores and physical stress to determine species richness and relative abundance.
Life-history trade-offs driving pathogen evolution and epidemiology
Anna-Liisa Laine
Trade-offs in life-history traits is a central tenet in evolutionary biology, yet their ubiquity and relevance to realized fitness in natural populations remains questioned. Trade-offs in pathogens are of particular interest because they may constrain the evolution and epidemiology of diseases. We find that the life-history trade-offs in pathogens are highly context dependent – influenced both by host genotype and coinfection status of the host. Hence, trade-offs may be a key mechanism for maintained variation in pathogen populations and in driving pathogen evolution. Moreover, we find that trade-offs mediated by pathogen local adaptation influence epidemiological dynamics at both population and metapopulation levels.
Life history and above-belowground interactions
Gerlinde B. De Deyn
Research over the last decades has demonstrated the importance of above- and belowground biota, both from the perspective of plant growth suppression and promotion. Many studies revealed intriguing indirect interactions between aboveground and belowground organisms and suggest that these can change according to order of arrival of the different biota and plant ontogeny. However most experiments on above-belowground interactions were of short duration and extrapolation to eco-evolutionary dynamics and changes in life history traits remains difficult. A key challenge therefore will be to place the findings of the simplified studies on above-belowground interactions in a realistic setting and derive implications for life history and plant community dynamics. Using the concept of trade-offs in growth and defense we can however postulate that plants in resource rich environments should grow, reproduce and disperse fast while plants in resource poor environments cannot grow fast yet live and reproduce long and invest in structural defences. Does this concept also hold for plants that grow in the same environment and what are the implications for plant-community dynamics? Recent research shows that plants selected over eco-evolutionary time in interspecific competition increase their investment in growth, likely trading-off with reduced defense against specialist herbivores and pathogens. Importantly in order to understand the costs and benefits of a plant strategy for different life stages and its impact on plant community dynamics it is required to also include indirect effects trough plant legacies via litter inputs and plant associated biota. Overall optimal life history strategies are not easy to predict as they are dependent on community context and resource levels. It is however clear that interactions with below- and aboveground biota during and afterlife need to be considered in a general frame-work of life history syndromes.
Life-history traits and the properties of meta-ecosystems: a theoretical perspective
François Massol
For most biologists, life-history traits are implicitly linked to the study of population demographics in a single species or, more rarely, to the study of coexistence conditions in ecological communities. However, the fact that life-history traits have an impact on ecosystem properties is yet to be fully grasped and acknowledged. Here, I will give some examples of theoretical models which make an explicit link between life-history traits and the functioning, stability and complexity of ecosystems. My presentation will mostly be focused on dispersal as a meaningful life-history trait affecting these ecosystem properties. In the case of dispersal, the mechanism linking trait value to ecosystem properties such as functioning or complexity is based on the simple fact that organisms that move “carry” their vital rates and their material/energy content with them as they migrate. Based on recent empirical literature, I will argue that other, more intricate links between life history and ecosystem properties might be found by studying the reciprocal feedbacks between ecological stoichiometry and life-history traits as nutritional constraints can partially determine life-history traits and different trait values can correspond to different stoichiometric needs and, hence, lead to different equilibrium levels of chemical elements in their environments. The issue of “scaling up” life histories thus amounts to bridging some gaps between the metabolic theory of ecology, ecological stoichiometry and population biology.