Introduction to the Symposium: What is Evolutionary Physiology?

The Evolution of Functional Traits in Plants: Is the Giant Still Sleeping?

Nature presents a staggering diversity of life history strategies, ranging from rapid to slow onset of sexual maturity, short or long life, low or high number of offspring, and much more. Each species-specific life history trait reflects on the one hand specific adaptations to unique environments, e.g., nutrient availability, predation, parasite load, seasonality; and on the other hand, depends on past demographic constraints, such as population bottlenecks, migrations, etc. Studying life history diversity in nature and in the laboratory ultimately aims to identify the ecological, demographic, and intrinsic causes contributing to species-specific growth rate distributions, lifetime reproductive outcomes, as well as lifespans. However, for most species, we cannot rewind the evolutionary and demographic past to identify the causal chain of events leading to the present life history traits. We can infer past events only by sampling extant populations. In silico evolution has the advantage of providing complete time resolution for the events driving life history evolution and enables to directly test the impact of ecological and demographic variables on the evolution of life history traits. We developed AEGIS (Aging of Evolving Genomes In Silico), a software for individual-based modeling of life history trait evolution at the genotype and phenotype level. AEGIS models life history traits evolution in response to a set of factors, including resource availability, extrinsic mortality induced by predators or parasites, different levels of germline mutation rates, population size, sexual vs. asexual reproduction, and more. AEGIS serves as a powerful tool to model life history evolution and allows for parameter inference against ground truths. AEGIS can help generate estimates for the evolution of different life history traits, such as age-dependent mortality and reproduction, in response to different selective pressures and intrinsic genetic constraints.

BackgroundControl of intermediate host snails using molluscicides for the control and/or elimination of schistosomiasis is a strategy in line with WHO recommendations. Niclosamide is the main chemical molluscicide recommended by WHO. However, except the immediate killing of the snail, the extent of the impact of the molluscicide application on the evolution of snail life-history traits, in relation to recolonization of treated sites is not well known. This study aimed to characterize the spatial variation of life-history traits of populations of the freshwater snail Bulinus truncatus, in relation to niclosamide spraying in the field.From 2016 to 2018, we conducted a trial, using niclosamide to control the intermediate host snails for interrupting the seasonal transmission of urinary schistosomiasis in northern and central Côte d’Ivoire. Five villages (sites) were considered, including three test and two control villages. In the test villages, the molluscicide was sprayed in habitats harboring B. truncatus snails three times a year (November, February–March and June). We sampled six B. truncatus populations: two populations from the control villages without any treatment; one collected before treatment and three sampled 2–3 months after treatment of the site with niclosamide. The snail populations were monitored for several life-history traits, including survival, growth, fecundity and hatchability, under laboratory conditions, over one generation (G1). We tested the population, region (North/Centre) and treatment status (treated/untreated) effects on the variation of the measured life-history traits and correlations between pairs of traits were estimated.ResultsOn the whole, the traits varied among populations. The risk of death was lower in northern populations compared to central ones. The age at first reproduction was reached earlier with a smaller size of snails in northern populations. Values of first reproduction features (size and fecundity) were lower in treated snail populations. The overall growth of untreated populations was higher than that of treated ones. The late fecundity and egg hatching were higher in northern than in central snails. At first reproduction, age was negatively correlated with some fecundity parameters. However, growth was positively associated with fecundity.ConclusionsOur study showed a spatial variation of life-history traits in B. truncatus snails. The mollusciciding seems to have led to the depression of some life-history traits in the snail populations. However, investigations should be carried out over several generations of snails to better clarify the impact of niclosamide on the evolution of the life-history traits.

10 - Life History Evolution in Metapopulations

Evolutionary physiology is the emerging physiological discipline. Unlike environmental physiology or ecophysiology, whose definitions have long been made quite clear, evolutionary physiology has a broader scope of objectives, and its definition lacks a concise treatise. This paper presents the argument that the lack of a common definition of evolutionary physiology is retarding the unification of the mechanistic and amechanistic physiological sciences, a multidisciplinary obligation crucial for a holistic understanding of a physiological basis of fitness. The divide between mechanistic "how" questions, devoted primarily to homeostasis, and evolutionary "why" questions, concerned with understanding phenotypic and genotypic physiological variation, remains broad and is currently not conducive to synergy in the physiological disciplines. Unification may be facilitated, however, by embracing a common currency of measurement and analysis. A likely candidate is the cascade of energy from the environment to offspring and the evolution of physiological form and function, including homeostasis, associated with power management. This currency approach seeks to identify an energetic basis of fitness, namely, whether or how the evolution of life-history traits is influenced by energetic constraints and/or trade-offs.

1. This study investigates the evolution of life-history traits in parasitic and free-living nematodes. A database on 35 species was assembled for values on: body size of female nematodes; egg production; life expectancies of both adult and free-stages; the length of maturation time for free-living nematodes and prepatent period for parasites (time needed for an infective stage to reach maturity in its definitive host). Comparative methods were used to account for the effects of phylogeny. 2. The well-known allometries of life-history traits with body size were found, such as the allometry between size and total fecundity. Daily fecundity and prepatent period of parasitic nematodes are both correlated with body size, suggesting that delaying maturity increases fecundity. 3. Phylogeny affects relationships between investigated life-history traits, i.e. daily reproductive output (b) and female life expectancy (1/M). 4. Prepatent period (a) in parasitic nematodes is equivalent to maturation time (a) of free-living nematodes. 5. A search was carried out for life-history invariants (Charnov 1993). There was no correlation between prepatent period (a) and daily reproductive output (b) and hence no invariant ab. This could be explained by constrained life styles of reproduction among Nematoda. Indeed, invariant aM (or aM, where M is the mortality rate of adult stage) were found for both parasites of vertebrate ((aM) = 0.23) and free-living, plant and insect nematodes ((aM) = 0.50). 6. A causal chain of evolution of life-history traits of parasite nematodes is proposed and discussed. It is suggested that adult mortality is the main factor driving the evolution of life-history traits.

A behavioral perspective on fishing-induced evolution

The isolated watersheds of the southwestern Andean Altiplano constitute a natural laboratory to study the evolutionary divergence of freshwater biota. Field observations showed that Biomphalaria snails from Parinacota, Colpa, and Caquena have different shell sizes. We performed morphometric analysis and common garden experiment to evaluate whether the observed shell variation has a genetic base and if this variation is manifested in other morphological characters and life history traits. Network analysis revealed that the snails of Parinacota form a lineage genetically distinct from Caquena and Colpa. The morphometric analysis of the shell showed that the Parinacota snails were larger than Caquena and Colpa, both in nature and laboratory conditions, but there was no evidence of difference in the shape of the shell when compared using multivariate analyses. The number of eggs per ovicapsule was the only life history trait that was significantly different between lineages, although this difference may be also attributed to size of the progenitor; the oviposition rate did not differ between lineages or localities, and the hatching size and growth rate differed only at the locality level, not lineages. The results suggest that shell size of the snails has a genetic basis associated to the phenotype, while the expression and evolution of life history traits in extreme high environments are highly influenced by proximal causes.

Some aspects of human life history are unique among primates. Most notably, humans have a younger weaning age, a later age at first parturition, a shorter female reproductive period, and a longer lifespan than other living hominoid species. Obtaining a better understanding of when and how life history changed during human evolution is important to those studying the evolutionary developmental biology of extinct hominins, as life history traits pace developmental processes. Life history traits are thought to be linked via tradeoffs, such that changes in early life history traits directly affect those that follow later in life, and vice versa. However, it is also worth considering how changes to a single life history trait may indirectly affect other traits by way of modifying selective pressures acting on individuals and groups. For example, because they affect the size and demographic structure of a group, late life history traits (e.g., lifespan) may also affect the evolution of life history traits that occur earlier in life, but by modifying selective pressures acting on juveniles rather than by triggering a physiological tradeoff. This review marks an effort to begin to disentangle the ways in which early and late life history traits may affect each other both directly and indirectly. We concentrate on female life history characteristics. First, we review previous research on the evolution of the postmenopausal lifespan in women. Next we discuss recent findings concerning the relationship between the optimal length of the female reproductive period, mortality, and weaning age that show that selection favors a shorter female reproductive period in the presence of a younger weaning age. We discuss the implications this finding holds for understanding the evolution of life history traits that are of particular interest to developmental biologists.

An important driver of evolution in viruses is natural selection to optimize the use of their hosts' genetic network. To learn how viruses respond to this pressure, we disrupted the genetic network of Escherichia coli to inhibit replication of its virus, bacteriophage lambda, and then observed how λ evolved to compensate. We deleted E. coli's dnaJ gene, which lambda uses to initiate DNA replication. Lambda partially restored its ability to reproduce with just two adaptive mutations associated with genes J and S. The location of the mutations was unexpected because they were not in genes that directly interact with DnaJ, rather they affected seemingly unrelated life history traits. A nonsynonymous J mutation increased lambda's adsorption rate and an S regulatory mutation delayed lysis timing. Lambda also recovered some of its reproductive potential through intracellular mutualism. This study offers two important lessons: first, viruses can rapidly adapt to disruptive changes in their host's genetic network. Second, organisms can employ mechanisms thought to operate at the population scale, such as evolution of life history traits and social interactions, in order to overcome hurdles at the molecular level. As life science research progresses and new fields become increasingly specialized, these results remind us of the importance of multiscale and interdisciplinary approaches to understand adaptation.

A life history can be viewed as a suite of co-adapted traits fashioned by natural selection to solve a particular ecological problem (Stearns 1976; Tuomi et al. 1983). Selection may act on individual traits in different manners, producing an overall life history that is a compromise among varying selection pressures. Life histories are thought to vary among populations within species, and among species, in a manner that reflects adaptation to local environmental conditions (e.g. Leggett and Carscadden 1978). Because much of the variation in life history traits may have a genetic basis, conditions experienced by a taxon in the past may have moulded some aspects of life history that are not currently adaptive (Ballinger 1983; Dunham et al. 1988). Therefore, phylogenetic constraints and historical relationships among populations and species must be accounted for in assessing the evolution of life histories (Wanntorp et al. 1990). The evolution of life history traits may be further constrained by genetic correlations and covariances among characters (Trendall 1982; Tuomi et al. 1983; Gaillard et al. 1989) and by physiological and energetic limitations on variation.

Arabidopsis thaliana and some of its close allies have been a model system for genetics, developmental biology, and molecular biology for some time. More recently, they have been adopted by an increasing number of laboratories involved in evolutionary ecological research. In this paper, I illustrate some of the methods and advantages concerning the use of Arabidopsis to study selection and the constraints imposed on it by the genetic architecture underlying morphological and life history traits. Populations of A. thaliana and closely related species show a wider ecological variance than had been suspected, and it is increasingly clear that even such a relatively simple organism presents endless challenges to ecologists and evolutionary biologists. The study of the evolution of life history traits in this group also provides us with an invaluable opportunity to advance our search for ways to integrate biological knowledge at the organismal and molecular levels. At the same time, these efforts also yield a better understanding of the type of research that can be carried out independently at these two levels of the biological hierarchy.

Several goals of evolutionary biologists can be approached by comparisons of species that occupy different habitats or that have evolved distinct suites of life history characters. One is to determine the ecological conditions favoring particular morphological or life history traits, and another is to detect adaptive combinations of traits that have ‘‘coevolved.’’ Recently, due to the development of statistical tools that use hypothesized phylogenetic relationships to detect the joint evolution of life history and ecological attributes among taxa, the comparative analysis of plant life history traits has enjoyed increased attention. Silvertown, Franco, and Harper responded to this interest by convening in 1996 a Royal Society Symposium aimed in part to highlight alternative approaches to the analysis of comparative data. This book represents the outcome of this meeting and includes 15 chapters, most of which use comparative data to interpret patterns involving the distribution of plant life history, mating system, or reproductive traits across taxa and environmental conditions. In addition, one chapter (by Michael Donoghue and David Ackerly) explores the effects of uncertainty in phylogenetic reconstruction on the outcome of one statistical test that makes use of phylogenetic information. Three chapters provide reviews of mathematical models: one concerning the allocation and packaging of resources among flowers and fruits (by Lawrence Venable); a second evaluating the relative importance of the automatic selfing vs. reproductive assurance hypotheses for the evolution of self-pollination and the use of coalescent theory to detect evolutionary events associated with the evolution of self-fertilization from outcrossing ancestral taxa (by Daniel Schoen, Martin Morgan, and Thomas Bataillon); and the third exploring the evolution of life history traits in heterogeneous environments (by Richard Sibly). It is tough to identify the best audience for this book. The chapters are neither review articles nor rigorous primary research articles. Most summarize new data analyses, but in few cases do they provide sufficient statistical and methodological detail to allow the reader to evaluate fully their appropriateness or interpretation. Consequently, I would not recommend this book as the main focus, say, of a graduate seminar, unless it were to be accom

Evolution in response to a change in ecology often coincides with various morphological, physiological, and behavioral traits. For most organisms little is known about the genetic and functional relationship between evolutionarily derived traits, representing a critical gap in our understanding of adaptation. The Mexican tetra, Astyanax mexicanus, consists of largely independent populations of fish that inhabit at least 30 caves in Northeast Mexico, and a surface fish population, that inhabit the rivers of Mexico and Southern Texas. The recent application of molecular genetic approaches combined with behavioral phenotyping have established A. mexicanus as a model for studying the evolution of complex traits. Cave populations of A. mexicanus are interfertile with surface populations and have evolved numerous traits including eye degeneration, insomnia, albinism, and enhanced mechanosensory function. The interfertility of different populations from the same species provides a unique opportunity to define the genetic relationship between evolved traits and assess the co‐evolution of behavioral and morphological traits with one another. To define the relationships between morphological and behavioral traits, we developed a pipeline to test individual fish for multiple traits. This pipeline confirmed differences in locomotor activity, prey capture, and startle reflex between surface and cavefish populations. To measure the relationship between traits, individual F2 hybrid fish were characterized for locomotor behavior, prey‐capture behavior, startle reflex, and morphological attributes. Analysis revealed an association between body length and slower escape reflex, suggesting a trade‐off between increased size and predator avoidance in cavefish. Overall, there were few associations between individual behavioral traits, or behavioral and morphological traits, suggesting independent genetic changes underlie the evolution of the measured behavioral and morphological traits. Taken together, this approach provides a novel system to identify genetic underpinnings of naturally occurring variation in morphological and behavioral traits.

The evolution of life-history traits is characterized by trade-offs between different selection pressures, as well as plasticity across environmental conditions. Yet, studies on local adaptation are often performed under artificial conditions, leaving two issues unexplored: (i) how consistent are laboratory inferred local adaptations under natural conditions and (ii) how much phenotypic variation is attributed to phenotypic plasticity and to adaptive evolution, respectively, across environmental conditions? We reared fish from six locally adapted (domesticated and wild) populations of anadromous brown trout (Salmo trutta) in one semi-natural and three natural streams and recorded a key life-history trait (body size at the end of first growth season). We found that population-specific reaction norms were close to parallel across different streams and QST was similar – and larger than FST – within all streams, indicating a consistency of local adaptation in body size across natural environments. The amount of variation explained by population origin exceeded the variation across stream environments, indicating that genetic effects derived from adaptive processes have a stronger effect on phenotypic variation than plasticity induced by environmental conditions. These results suggest that plasticity does not “swamp” the phenotypic variation, and that selection may thus be efficient in generating genetic change.