This workshop aims to clarify, update and expand on traditional evolutionary thinking by providing a platform for discussion. Critics have argued evolutionary studies very gene-centric and dismissive of other mechanisms contributing to evolutionary change. They call for a wider recognition particularly of:
• Niche construction theory
• Extra-genetic inheritance
• Developmental bias
• Phenotypic plasticity
And while the importance of these fields is backed by empirical evidence, wider recognition is trailing behind. We would like to change that. If this interests you, please join us and let's talk evolution…
All the accepted participants will be able to present their research either in the form of a talk or a poster. Participants who wish to present a poster will introduce their poster as a mini talk to spark discussions.
Invited and confirmed as speakers are:
Scientific Organizers: Noémie Erin, Alice Feurtey, Dominik W. Schmid, Vandana R. Venkateswaran (MPI for Evolutionary Biology, Plön)
This talk will have two parts. In the first, I will provide a brief general introduction to the logic and objectives of the extended evolutionary synthesis (EES). I will describe why it was proposed, how it can be of service, and why expanded inheritance, developmental bias, plasticity and niche construction were selected as foci. I will go on to briefly sketch what it is about each of these topics that leads some researchers to believe a broader causal structure for evolutionary theory might be useful. The EES should be regarded as a benign initiative, and a means to an end rather than an end in itself; it is a distortion to portray it as a (call for) paradigm shift or attack on evolutionary biology. In the second part I will draw on my own research into human evolution to illustrate how bias, plasticity, expanded inheritance and niche construction are all now commonly thought to have played important roles. I will conclude by suggesting that different evaluations of the importance of these foci in part stem from alternative conceptions of development, which vary substantially across academic fields.
Lewontin`s (2010) four metaphor-free conditions for evolution explain neither diversification nor niche construction in themselves. Adding two more assumptions – one about the necessity of regulated population growth (“limitedness”) and another about the constraints on emerging variations (“interdependence”) – may explain both. Model-independent derivation of the conditions for competitive exclusion and robust coexistence (Meszéna et. al. 2006, Barabás et. al. 2014) follows from the complete set of metaphor-free assumptions. This set of conditions explains the tendency for diversification, provides direction to the population dynamic processes and to evolution in the long run. Our textbook confined to the study of the distribution and abundance of species and structured according to the complete set of principles (Pásztor et. al. 2016) proves their essential role in ecology. A uniform definition of fitness of reproductive units (genes/haplotypes, complete genomes of clonally reproducing individuals, species identity of sexually reproducing individuals) may unify ecological and genetic approaches illustrating that a system of alleles is “perfectly isomorphic” (Hardin, 1960) with a system of species in this sense. The concept of niche construction due to interactions between the organisms and their biotic or abiotic environments can be integrated via the theory-based niche concept as the way of population regulation. Interactions between the organisms and their environments lead to positive or negative feed-backs between their density and rate of population growth (fitness). It is impossible to define niche and niche construction without considering the impacts of population growth on the environmental factors and the sensitivities of population growth on these factors (i.e. the feed-back loops). This reinforces the need for the inclusion of limitation of population growth and interdependence of organismal traits into the core of evolutionary theory, just like Darwin did. Barabás, G., Pásztor, L., Meszéna, G. and Ostling, A. (2014). Sensitivity analysis of coexistence in ecological communities: theory and application. Ecology Letters, 17: 1479-1494. Hardin, G. (1960). The Competitive Exclusion Principle. Science 131: 1292-1297. Lewontin, R.C. (2010) Not So Natural Selection. The New York Review of Books May 27. Meszéna, G., Gyllenberg, M., Pásztor, L. and Metz, J.A.J. (2006). Competitive exclusion and limiting similarity: a unified theory. Theor Popul Biol, 69: 68-87. Pásztor, L., Botta-Dukát, Z., Magyar, G., Czárán, T. and Meszéna, G. (2016). Theory-Based Ecology: A Darwinian approach, OUP Oxford. pp.301.
Programmed cell death (PCD) increases the fitness of multicellular organisms via tissue homeostasis and organismal development. In unicellular organisms, however, PCD takes on additional evolutionary significance because the cell is the organism. Here, the definition of ‘true’ PCD in unicells as “an adaptation to abiotic and biotic environmental stress” is adopted and justified with empirical data. The evolution of the other forms of death, ersatz PCD and incidental death, are not dealt with. The evolutionary ecology of PCD in microbial communities will be presented from three perspectives. First, the published theoretical and empirical data for the evolution of PCD as a group or kin level phenomenon will be reviewed. These data come from a diverse range of single celled eukaryotes including Saccharomyces, Chlamydomonas, Dictyostelium, Leishmania and Peridinium species and the prokaryotes Escherichia and Streptomyces. Second, the previously unexplored perspective of PCD evolution by niche construction will be presented. Data from Dunaliella salina and Halobacterium salinarum demonstrate that D. salina significantly modifies the microenvironment via PCD. The environmental modification has a positive fitness impact on both D. salina and a naturally co-occurring archaeon H. salinarum. The simplified criteria for evolution by niche construction are met, however, there is a caveat. It will be claimed that an interpretation of the evolution of PCD by niche construction still requires cooperation between individuals such that there is selection at the group or kin level. Third, the marked plasticity of the PCD phenotype is associated with the evolution of alternate life history strategies. In some instances, one variant of the PCD trait is associated with a multicellular-like life cycle. This is the case in Streptomyces and Dictyostelium species. In others, the induction of sexual reproduction in unicellular and multicellular volvocines appears to be an alternate response to PCD. The plasticity of the PCD stress response may lead to a number of phenotypes within a clonal population, including programmed death, cell-cycle arrest, encystation and sexual reproduction. The three perspectives discussed here (group selection, niche construction and phenotypic plasticity) will illustrate alternate contextual approaches to investigating the complex phenomenon of PCD in microbial communities.
Feedbacks between heritable trait change and the dynamics of populations, communities, and ecosystems are central to evolutionary ecology. Models of these feedbacks require a strong understanding of the ecological dynamics of natural selection, and the effects of trait distributions on these dynamics. Multiple theoretical frameworks have been proposed to study feedbacks that vary in their assumptions about the timescales of trait change and the mechanics of adaptive evolution. Experimental tests of feedbacks are common in lab-based studies, but rare in more natural settings. Here, I present several experimental tests of eco-evolutionary feedbacks in large outdoor mesocosms, using stickleback as a model organism. I find evidence for key components of eco-evolutionary feedbacks: i) stickleback ecotypes differentially modify their biotic and abiotic environment, ii) ecosystem modifications are persistent over time, and iii) they affect selection pressures on subsequent generations. Overall, this work suggests that adaptive phenotypic evolution can influence ecosystems in a way that affects selection on heritable phenotypes.
Mini-Talks of poster presenters Karina Vanadzina, Arina Maltseva, Christoph Gahr
Mini-talk + poster
Around a quarter of all recognised families of ray-finned fishes (Actinopterygii) exhibit some form of parental care to increase the survival rate of their offspring1.The effectiveness of care in externally fertilised fishes can be significantly enhanced by the presence of a nest. A well-constructed and concealed nest provides shelter from predators and maintains sufficient levels of water flow that oxygenates eggs and removes metabolic waste. On an evolutionary timescale, the presence of a nest generates selective pressures for the nest holder to defend and maintain its nest and for nearby animals to exploit the structure2. In this study, undertaken as part of a PhD project at the University of St Andrews, I assess the impact of niche construction in freshwater and marine fishes using phylogenetic comparative methods, with a particular focus on nest building and parental care. So far, the process of nest construction in fish has only been investigated in experimental studies using model organisms such as sticklebacks and sand gobies. This study is the first to explore the global spread of nest-building habits in fish using the latest comparative methods. My work fits within a framework of a larger project on niche construction that tests whether artefact building generates consistent and predictable selection pressures on a macro-evolutionary scale across a broad taxonomic spectrum of animals. 1. Wootton, R. J., and C. Smith. 2014. Parental care. Pages 251–279 in R. J. Wootton and C. Smith, eds. Reproductive Biology of Teleost Fishes. Wiley-Blackwell, Chichester, U.K 2. Laland, K., Odling-Smee, J. & Endler, J. Niche construction, sources of selection and trait coevolution. Interface Focus 7, 20160147 (2017).
Mini-Talk + poster
In theory, there are three possible ways a population can adapt to heterogeneous environments: (1) supporting genetic polymorphism on directly genetically determined traits and to distributing individuals-specialists between differential biotopes; (2) equipping individuals with phenotypic plasticity; (3) fixing some generalist genotype effectively functioning under any conditions (Scheiner & Lyman, 1989). Studying the relative importance of these processes in recently diverged species increases our knowledge on mechanisms of speciation. There are three closely related species of rough periwinkles in the North Atlantics: Littorina saxatilis, L. arcana and L. compressa, with the former being accepted as the oldest one (Reid, 1996; Doellman et al., 2011). These species exploit different reproductive strategies: unlike other two egg-laying species, L. saxatilis is ovoviviparous. They leave in sympatry in the intertidal area, however, L. saxatilis range expands to more stressful conditions, e.g. estuaries (Reid, 1996; Granovitch et al., 2004). Moreover, the two younger species occupy a narrow part of vertical shore profile only slightly overlapping with each other (L. compressa prefers lower and L. arcana – upper parts of the shore; Granovitch et al., 2013), fully covered by more broad area of L. saxatilis. Sympatric populations of all three species are characterized by comparable degree of genetic diversity (Doellmann et al., 2011), and those species are very close at the whole-genomic level (Panova et al., 2014). We compared physiological state of snails of all three species inhabiting different shore levels using proteomic and metabolomic analyses. Mating preferences of males were described as a part of behavior. L. saxatilis and L. arcana showed the same patterns: their proteomes and metabolomes were rather similar in terms of qualitative and quantitative characteristics; moreover, they changed in an analogous manner depending on shore level. Males of those two species demonstrated moderate choosiness readily copulating with males and females of both species. L. compressa showed a completely different pattern. Metabolomic and proteomic samples of this species grouped separately from those of L. saxatilis and L. arcana; the degree of intragroup diversity was significantly lower than in two other species; no shore level related variability was detected. Besides, males of L. compressa displayed strong preference for conspecific females. Thus, for some reason among populations of three closely related sister species living together, L. compressa exhibited a rather peculiar – constricted – pattern of functioning. In my presentation I will discuss a number of possible explanations to these remarkable differences. One of speculative conclusions is that key speciation events could be related not only to environmental shifts or niche expansion, but also to changes in a pattern of interaction with the same environment, a shift in a main adaptive strategy. Doellman MM, Trussell GC, Grahame JW, Vollmer SV (2011) Phylogeographic analysis reveals a deep lineage split within North Atlantic Littorina saxatilis. Proceedings of the Royal Society of London B: Biological Sciences 278(1722): 3175-3183. Granovitch AI, Mikhailova NA, Znamenskaya O, Petrova Yu A (2004) Species complex of mollusks of the genus Littorina (Gastropoda: Prosobranchia) from the eastern Murman coast. Zoologicheskij Zhurnal 83(11): 1305–1316. Granovitch AI, Maximovich AN, Avanesyan AV, Starunova ZI, Mikhailova NA (2013) Micro-spatial distribution of two sibling periwinkle species across the intertidal indicates hybrdization. Genetica 141(7-9): 293-301. Panova M, Johansson T, Canbäck B, Bentzer J, Rosenblad MA, Johannesson K, Tunlid A, André C (2014) Species and gene divergence in Littorina snails detected by array comparative genomic hybridization. BMC Genomics 15: 687. Reid DG (1996) Systematics and evolution of Littorina (No. 164). London: Ray Society. Scheiner SM, Lyman RF (1989) The genetics of phenotypic plasticity. I. Heritability. J Evol Biol 2: 25-107.
Mini-talk + poster
Differences in environmental conditions can drive divergent selection towards locally adapted ecotypes. In sticklebacks (Gasterosteus aculeatus), parasites are a major environmental factor, exerting strong selection pressure with regards to reproduction, predation and growth. These parasite communities vary strongly between habitat types (e.g. river or lake), imposing a need for ecotype dependent local adaptation of parasite resistance. Hence, stickleback ecotypes of similar origin (e.g. river or lake) should have evolved comparable parasite-specific resistance best suited for their respective habitat. To test whether this holds true on a global scale we exposed lab bred Canadian and German sticklebacks to a typical lake parasite, the trematode Diplostomum pseudospathaceum. Each fish was individually exposed to 100 Diplostomum cercariae and sacrificed 24h after exposure to measure infection rate and collect tissue samples for gene expression analysis (including sham-exposed controls). Our results show parallels in the discrepancy pattern for infection rates between Canadian and German river/lake pairs, with river fish exhibiting a generally higher infection rate than lake fish. We further investigated the underlying gene expression patterns of immune relevant genes to unravel the mechanistic basis for the convergent evolution between the river/lake pairs. Focusing on innate immune genes in particular, we find similar response patterns within ecotypes.
Evolutionary predictions can only be as good as the models on which they are based. Traditionally, evolutionary models are kept as simple as possible, with the idea that simple models are more easily tractable and that their conclusions are more general and robust. These models tend to focus on how selection acts on the phenotype and on the phenotypic response patterns to environmental stimuli, thereby largely neglecting the (epi-)genetic, physiological, and behavioural mechanisms underlying these phenotypes and responses. With the advent of mechanism-oriented fields like evo-devo or evolutionary systems biology this attitude is slowly changing. To synthesize these developments, I propose a new, mechanism-oriented framework that views the architecture of adaptation, rather than the resulting responses, as the primary target of natural selection. By means of general arguments and concrete example studies, I will demonstrate that this change in perspective has major implications: (1) it may lead to fundamentally different predictions concerning the course and outcome of evolution; (2) it sheds new light on the emergence and maintenance of genetic and phenotypic variation; and (3) it provides a new perspective on the speed of evolution and the potential of organisms to adapt to novel environmental conditions.
At the sea shores of the European part of Northern Atlantic, periwinkles of the genus Littorina (subgenus Neritrema) are represented by two sister groups of closely related species: “obtusata” (L. obtusata, L. fabalis) and “saxatilis” group (L. saxatilis, L. arcana, L. compressa). Moreover, most of the species, especially, L. saxatilis, tend to form ecotypes along shore’s ecological gradient. All these species live in sympatry and incomplete restriction of gene flow was shown within “obtusata” and “saxatilis” although, cryptic groups are fully isolated from each other. Based on both partial reproductive isolation and tendency of species to form ecotypes, species within cryptic complexes could be accepted as results of ecological speciation processes (possibly not fully finished yet). Sibling species of the subgenus Neritrema are well studied as a model system for ecological speciation and adaptation. Analysis of reproductive isolation mechanisms in this model system promises to turn up very fruitful. It could elucidate when does reproductive isolation form during ecological speciation and is it a key event for speciation. Traditionally the appearance of a reproductive barrier is attributed to reinforcement, natural selection against hybrid forms (this may be regarded as a kind of postzygotic barrier). Nevertheless, there are just a few direct studies on mechanisms of reproductive barriers in the Littorina model system. Our studies of mating behavior in Neritrema species showed that there is no reproductive isolation before insemination in any level: all mating variant can be found in natural populations. Thus, if reproductive isolation is implemented in prezygotic level, there should be gamete incompatibility (according to the wide Mayr’s definition). Such mechanisms are well studied in insects but not in internally fertilized molluscs. We identified the LOSP protein potentially involved in gamete interaction and related to formation of reproductive barriers. LOSP initially detected in L. obtusata sperm is a paraspermal protein, present in all Neritrema species. Most probably it is released after insemination and may be involved in reproductive isolation between Neritrema species via sperm competition mechanisms. Thus, comparison of LOSP diversity, on the one hand, and physiological similarity of initially specified subpopulations, on the other hand, can reveal: do ecological adaptation and genetic flow restriction form simultaneously? The project is supported by the grand of Russian Foundation for Basic Research number 18-34-00873.
A vast majority of studies in sexual selection focus on only two mechanisms, male -male competition and female choice. Yet clearly, both male mate choice and female competition are important factors in sexual selection. I will review this – with a focus on male mate choice -, using Livebearing fishes of the family Poeciliidae as an example. There are surprisingly many examples of male mate choice in this taxonomic group. Males in this group contribute nothing but an ejaculate to the offspring, making the evolution of male mate choice unlikely. But several studies found clear preferences in males based on differences in female quality. Most commonly, male preferences for female body size have been documented, likely related to increased fecundity found in larger females. Finally, I will point out a number of open questions in the field, including the role of female competition, and the relationship of male mate choice with female ornaments.
Phenotypic plasticity, once a somewhat controversial topic in evolution, is now more broadly recognized as an important mechanism by which organisms can tolerate variable environments and avoid extinction. In particular, it is now understood that phenotypic plasticity does not necessarily counteract evolution by natural selection, and that investigating the origins of phenotypic diversity often requires studying the interplays between plasticity and genetic evolution, including the evolution of plasticity itself. However, the contribution of phenotypic plasticity to adaptation and population persistence in new environments, beyond the usual range of variation, is a more recent and open question, fostered notably by the interest in understanding - or even predicting - population responses to global change. I will present results from of our research on this topic, based on simple quantitative genetic models of reactions norms. These models highlight some key parameters that are needed for better prediction of population responses to environmental change, but for which empirical measurements are stills scarce. One is the genetic correlation of trait values between currently common and rare/extreme environments, which determines constraints on reaction norm shapes. Another is environmental predictability or cue reliability, which may well differ between the previous and novel environment. I will end by discussing some of the challenges with relating these theoretical predictions to empirical measurements, with a particular focus on our current empirical work, notably on the halotolerant microalgae Dunaliella salina.
Theory predicts that adaptive plasticity in fitness-related traits may play a key role in establishment in novel environments, persistence in changing environments, and allopatric speciation. Yet testing these hypotheses is difficult, especially at the macroevolutionary level, due to the inherent difficulty of measuring plasticity. We exploit recent methodical advances to estimate the strength of plasticity and the environmental dependence of selection, the two key parameters linking plasticity and local adaptation, from observational data from a large-scale database of over one million individual records of adult damselflies and dragonflies and corresponding spring temperatures. Our aim is to elucidate the role that temperature-induced plasticity in timing of metamorphosis (phenological plasticity), a key life history transition, plays in macroevolutionary diversification. Specifically, we predict that: 1) the strength of plasticity should coevolve with the environmental dependency of selection and 2) the contribution of plasticity to local adaptation should be highest in extreme/recently colonized environments. Our analysis of over one million records from 49 species supports both predictions. First, we find correlated evolution of the strength of plasticity and the environmental dependence of selection. Second, we show that the contribution of phenotypic plasticity to within-species local adaptation increases during the recent, post-glaciation colonization of Northern regions. Our results suggest that phonological plasticity may have played an important role in temperate diversification in these insects. Moreover, an extensive long-term database of selection in wild populations allows the unique opportunity to validate these novel comparative approaches to the study of phenotypic plasticity.
Evolutionary adaptation is typically accredited to natural selection. However, natural selection can only adapt populations, and by itself has little to offer to locally maladapted individuals. Because of this, flexible individual responses have evolved that can help individuals to increase their fitness. By means of a simple yet apparently comprehensive classification framework, I will derive that only three such responses can exist (as appears to be confirmed from the social and economic sciences): adjustment of the phenotype (e.g. plasticity), adjustment of the environment (e.g. niche construction), and selection of the environment (e.g. habitat choice). I will then explore to what extent, and under what conditions, these flexible responses can additionally and independently drive adaptive evolution (touching upon discussions surrounding the Extended Evolutionary Synthesis and the Extended Phenotype). This framework can help to shift our evolutionary thinking from an organism- and gene-centred position towards that of the evolution of the organism-environment interaction via genetic and alternative hereditary means.
Gene expression is inherently plastic, and the expression profiles of ectotherm embryos differ substantially between incubation temperatures. We used an experimental approach to understand the relationship between short-term plastic responses and long-term evolutionary responses in transcriptomes. Wall lizards have been introduced to the UK numerous times over the last century, and several populations have adapted independently and repeatedly to the cooler climate by increasing their developmental rate. Using a split-clutch experiment, we asked how expression profiles at an early developmental stage differ between embryos of native and introduced populations at two different incubation temperatures. Accounting for divergence due to drift, we identified a set of genes that showed evidence for positive selection on expression in introduced, compared to native populations. Intersecting this set of genes with temperature-dependent gene expression in the native population shows that genes that evolved a putatively adaptive response to cool climate were predominantly drawn from the pool of genes that exhibits ancestral temperature-dependence in their expression. I discuss how these results contribute to our understanding of evolutionary implications of plasticity.
Our understanding of adaptive evolution is grounded in a deterministic view of genetic variants. Yet development takes shape through the interaction of an organism’s genotype with its environment, an interaction that can be surprisingly complex both within and across generations. How does this causal entanglement change our view of evolution? Ecological developmental biology explicitly examines phenotypic expression in environmental context. A suite of within- and trans-generational ‘eco-devo’ experiments with annual plants provides a case study that reveals the repertoires of adaptive and maladaptive plasticity inherent in individual genotypes, and points to newly expanded answers to three fundamental evolutionary questions: the nature of adaptation, the kind of biological information that is inherited, and how to define --and study—the process of evolutionary change.
Term “adaptation” means a feature or set of features making organism fitting to its environment. Adaptation as a process (making an organism adapted) is traditionally interpreted as being inextricably linked with action of natural selection (NS) as a main forming force during speciation. Nevertheless, there are at least two conceivable explanations of the fact of “organism to environment fitness” regarding NS as a subordinate, secondary factor. The first alternative explanation implicates the fundamental phenomenon of phenotypic plasticity. The homeostasis of an organism is tuned by environment through physiological and biochemical mechanisms, resulting in fitness to particular conditions. Long-term habitat change, which last during several generations, will lead to genetic “substitutions” of initially phenotypic adaptation to the genetic ones (Waddington, 1947, Schmalhausen, 1949, West-Eberhard, 2003, Kull, 2014). Typical physiological and biochemical patterns could be fixed at the genomic level if certain environmental patterns persist for a long time, for several generations. In this case, NS (together with stochastic genetic changes and mutation rate) is regarded as a secondary mechanism. According to such scenario, the genetic background of certain adaptive complex emerges when this adaptive complex does already exist. NS may play its secondary role at this step, contributing to appearance of optimal genetic machinery. The second conceptual approach appeals to the ideas of self-organization of living matter (Denton et al., 2003, Newman et al., 2006, Wills, 2009, Johnson, Lam, 2010). According to this, NS should be placed at least alongside the self-organization patterns to explain the mechanisms of evolution. Consequently, the notions on evolution as “selectogenesis” should be at least partly replaced by the notions of “orthogenesis”. The source of adaptivity within the self-organization conception is not obvious and may be described as follows. Any genetic or nongenetic variation of an organism is comprised (included) in a system of hierarchical multiple compensation, from the molecular to biocenotic levels. During its manifestation, the signal of variation passes through a series of “system filters” or “checkpoints” at the epigenetic, ontogenetic, physiological, behavioral, populational and biocenotic levels. Each “filter” is represented by multiple feedbacks maintaining the integrity of systems at every particular level and all the levels taken together. These “system filters” is where the adaptivity comes from making every individual an object for action of the Law of Multilevel Self-Organization. Thus, adaptivity originates on the basis of variations as a mandatory case of multilevel self-organization. The function of NS, in this way of thinking, is reduced to a secondary mechanism, discarding individuals incapable of effective self-organization.
Phenotypic plasticity and its converse (canalization) have been subject to many theoretical and empirical studies. Theory suggests that adaptive phenotypic plasticity can evolve in temporally or spatially heterogeneous environments through selection on the slopes or intercepts of reaction norms. For instance, Lande (2009, J. Evol. Biol. 22: 1435-1446) modelled reaction norm evolution following the invasion of a population in to a novel and extreme environment and he was able to partly capture the so-called "Baldwin effect". Modelling phenotypic plasticity as slopes of reaction norms and studying the evolutionary dynamics of such reaction norm slopes and their intercepts is a promising approach, but sofar there are few empirical quantitative studies investigating the strength of selection on reaction norm slopes or intercepts. In contrast, there are many empirical studies demonstrating genetic variation in reaction norms through family-based studies on genotype-by-environment interactions. Here, I will present some new empirical field data where we have tried to fill in this gap. We have quantified between-individual variation in reaction norm slopes and intercepts of body temperature changes in relation to the external thermal environment in two closely related and phenotypically similar species of damselflies (genus Calopteryx). We have also estimated the strength of selection on both slopes and intercepts in the field of these two damselfly species. Our results show that sexual selection does in some situations favour thermal canalization rather than thermal plasticity. These results will be discussed in relation to some general issues such as the roles of plasticity, canalization and regulatory behaviours in evolution.
With mini-talks by poster presenters Rienk Fokkema, Daniel Romero Mujalli, Helen Spence-Jones, Mark Chapman
Mini-talk + poster
Mini-talk + poster
Mini-talk + poster
Mini-talk + poster
Bias in how development generates a morphology can in theory constrain the independent evolution of traits sharing ontogenetic pathways, making certain evolutionary changes more likely than others. The eyespots on butterfly wings are classic examples of serially repeated pattern elements and have been a focus for evo-devo research over recent decades. Previous work on a model species of mycalesine butterfly, Bicyclus anynana, revealed how the size and colour composition of individual eyespots are modulated in development. Experimental evolution also showed that the relative size of different eyespots on a wing surface is highly flexible, but that the relative proportion of their colour rings is largely inflexible, presumably due to a shared developmental process hindering independent evolutionary changes in colour-composition. We have now surveyed the diversity in these eyespot traits across an extensive phylogeny of mycalsine butterflies. Results are largely consistent with the experimental evolution in our model species with the exception of a diverse clade on Madagascar. Eyespot colour proportions generally display similar ratios across species consistent with a major role for developmental bias in shaping evolutionary diversification of colour-composition. However, some Malagasy species have gained independent control of eyespot colour elements enabling a wider exploration of morphospace. We have investigated the formation of this novel phenotype using micro surgery to manipulate eyespot development in early pupal wings in a Malagasy species. The results show how the bias has been broken by modulating the response of different areas of wing tissue to a conserved ancestral organising signal. Our results demonstrate how developmental bias can potentially constrain the evolutionary independence of traits, but that at a macro evolutionary level such bias can be broken through innovative developmental reorganisations, with subsequent rapid change in phenotypic evolution.
Developmental bias is the non-random generation of phenotypes as a result of developmental processes; making some (combinations of) phenotypes more likely than others. Developmental bias is clearly widespread, but there is little insight in the generality of the patterns, nor in their evolutionary consequences. Here, we take a meta-analytical approach and test whether environmentally induced phenotypic variation has evolutionary potential, as predicted under the ‘plasticity-first’ hypothesis. We collect phenotypic and genetic variance-covariance matrices (P- and G-matrices) for populations in their ancestral and a novel environment and test whether (a) environmentally induced variation is biased, and (b) if this bias is concordant with genetic variance-covariance matrices. Alignment between genetic and environmentally induced components of phenotypic variation can help to reveal how developmental biases evolve, and the extent to which plastic response has evolutionary potential.
Natural selection and phenotypic plasticity can both contribute to ecologically relevant trait variation within and among populations. Previous work suggests that variation in cryptic pigmentation of freshwater isopods (Asellus aquaticus) has evolved in response to predation pressure by fish in habitats with varying macrophyte cover and coloration. However, more recent evidence suggests that the development of isopod pigmentation can also depend on the nutritional environment during development and may be of importance in determining the trajectory of the life-history that follows. To address this, we investigated i) the degree and potential costs of developmental plasticity in pigmentation and body size of the freshwater isopod Asellus aquaticus and tested ii) for genetic variation in plasticity among families. In a series of laboratory experiments we reared offspring from 30 isopod families in common garden under two different diets (high / low nutrient concentration). We found that differential nutrient supply lead to consistent differences in pigmentation: isopods reared under high nutrient diet developed stronger pigmentation earlier on than isopods reared under low nutrient diet. Differences in growth rates were small and inconsistent among families. Survival was lower in the high nutrient environment, where isopods also died earlier than in the low nutrient environment. Moreover, all diet based effects on pigmentation, body size and survival were strongly affected by family descent. Overall our results show that there is genetic variation in plasticity associated with the development of A. aquaticus, suggesting that selective processes may interact with plasticity in the given population.
With mini-talks by poster presenters Joanna Summers, Michael Barnett, Miguel Gomez and Edith Invernizzi
Mini-talk plus poster
Mini-talk + poster
Mini-talk + poster
Recent experiments have shown that spontaneous epigenetic variation exists. This means variation in heritable epigenetic changes that behave in a manner analogous to genetic variation. Currently this sort of variation is best understood for DNA methylation in plants. We know that spontaneous DNA methylation changes happen, and the rate of these changes is many orders of magnitude higher than for genetic mutations. Based on theoretical models the extent on how epigenetic variation changes evolutionary dynamics depends on the properties of epigenetic variation. Namely the rate of spontaneous epigenetic changes, their stability, and the distribution of their phenotypic effects. If both epigenetic and genetic variation are present, and they both can affect the phenotype, this leads to an evolutionary dynamic where adaptation proceeds first using epigenetic variation and subsequently the same phenotype is fixed using genetic mutations. The question remains does this happen in the real world. We studied this question experimentally using the single celled algae Chlamydomonas, and observed that manipulation of the epigenetic system affected adaptation. Moreover, we observed many DNA methylation changes, that could not be explained by cis-acting mutations. In summary, epigenetic changes have the potential to influence adaptation, but to determine their importance we need better estimates of their phenotypic effects.
...and what we can do about it. In my talk I will take a look at the history of science and outline that extra-genetic inheritance is a classic Duhem-Quine problem. I will explain why the representation of extragenetic inheritance as a fairy-tale organism with apparently incompatible characteristics (like a platypus) can contribute to understanding the current debate about its relevance. I will explain that current evolutionary models clearly point the way forward for groundbreaking empirical research and argue that unconventional and above all interdisciplinary approaches are needed. Finally, I will summarize my own current work on the interaction of environment and epigenetics in wild fish.
Evidence that non-genetic traits can be transmitted to future generations has caused a surge in interest in epigenetic inheritance. If it were found to be common across species that adaptive traits acquired during an organism’s lifetime can be passed on to future generations it would prompt a rethinking of evolutionary theory. Yet solid evidence for epigenetic changes being both adaptive and heritable (i.e., adaptive epimutation) is scarce. What features of a species would make it most prone to evolve a system of adaptive epimutation? Here we use a mathematical model to investigate if and when adaptive epimutation would be expected to evolve when selection pressure varies spatially. We show that spatial variation in selection provides indirect selection for adaptive epimutation. When the migration rate is low, the strength of indirect selection in favour of adaptive epimutation increases with the migration rate between patches. Yet, when migration rate becomes larger, the opposite trend is observed. We predict that species with moderate migration rates inhabiting heterogeneous environments would be most likely to evolve systems of adaptive epimutation, but only if costs of producing such systems are not too high.
Much discussion has recently arisen in relation to the Extended Evolutionary Synthesis to the effect that the Weismann barrier between germ and soma may at times be effectively trespassed by processes of trans-generational epigenetic inheritance and non-genetic inheritance. This is extremely significant as the strict separation between soma and germ and thus the prohibition of the Inheritance of Acquired Characteristics represents one of the most salient features of the account of evolution proposed by the architects of the modern synthesis in the first half of the 20th Century. A relevant wealth of research in very many different areas of epigenetics, niche construction and ecological inheritance theory and evo-devo shows, however, that cases in which this separation fails to hold do constitute the norm rather than the exception in many biological contexts. This seems to entail that our traditional view of evolution should be made broad enough so to accommodate the effects of phenotypic flexibility and behavior on the direction of evolutionary change. This paper addresses current research on cultural evolution and genetic accommodation with a view to showing that cultural trans-generational inheritance while being way more broadly prevalent across many animal species than it was once thought, signals one relevant way for heredity to take place in manners not quite contemplated by the modern synthesis. Taking a look at human (and more generally animal) cultures by using critically some ideas developed by Ernst Cassirer´s philosophy of culture I will show how symbols and symbolic activity are regularly intertwined in the very process by which adaptive traits are transmitted on to the next generations of individuals. The paper will show that this is especially the case when it comes to processes of co-evolution in which both humans and other biological species are involved. The point will be advanced that such co-evolutionary scenarios far from representing marginal and relatively unimportant footnotes in current Evolutionary Biology, are actually becoming rampant within the biosphere after the advent of the Anthropocene. Secondly, I will also argue that even in other cases where behavior can hardly be interpreted as genuinely symbolic, it is still possible to show that animal cultures and traditions do mediate in the process by which biological individuals do pass information on to their offspring. To be sure, this is not to say that the gen´s eye view of evolution is plainly false but certainly helps understand the extent to which some processes in evolution require an inversion in the direction of the causal arrow. If so, this would entail not only that our traditional view of evolution is in dire need of a rethink but that our more general distinction between natural and cultural sciences ought to be reconsidered in a new and more multidimensional light as well. To put it succinctly: while the relationship between evolution and culture has often been regarded as one where evolution explains culture off, what the new strands in biological thinking show aplenty is that both evolution and culture ought to be thought as causally interacting with each other.
Melanie J. Heckwolf1, Britta S. Meyer1, Robert Häsler3, Sören Franzenburg3, Christophe Eizaguirre2 and Thorsten B. H. Reusch1 * Both authors contributed equally to this work 1 Evolutionary Ecology of Marine Fishes, GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany 2 School of Biological and Chemical Sciences, Queen Mary University of London, London, UK 3 Institute of Clinical Molecular Biology, Kiel University, Kiel, Germany Epigenetic variation is a recently discussed mechanism that allows phenotypes to vary without the prerequisite of DNA sequence based genetic change. If epigenetic marks are heritable, this might provide an accelerated pathway for subsequent adaptive evolution. However, the relative contribution of genetic and epigenetic variation to adaptation and the stability and heritability of underlying epigenetic marks remain unclear. We assessed the natural epigenomic variation (DNA methylation) in three marine three-spined stickleback populations originating from different salinity regimes in the Baltic Sea and North Sea (high, mid and low salinity). Additionally we collected sticklebacks from one population (mid salinity), bred them in the lab and acclimated them over one and two generations to the salinity levels of the two remaining populations (high and low salinity). Using reduced representation bisulfite sequencing (RRBS), we compared DNA-methylation between the two wild populations, the within-generationally and the transgenerationally acclimated groups to provide a comprehensive analysis of stability and inducibility of natural epigenomic variation. While most CpG methylation revealed to be stable, we found methylation of genes associated to osmoregulation and oxygen consumption to be inducible by experimental salinity change. Other genes influencing vitamin biosynthetic processes or skin development were stable within the population regardless of their treatment conditions. Comparing these findings to RNA-Seq data and life history trait measurements of the same individuals, we are not only able to assess the stability of epigenetic marks, but further show their impact on the (molecular) phenotype. Our holistic approach provides insight on epigenetic patterns in the wild and their potential role in adaptation and experimental acclimation.
Mini talks by poster presenters Britta Meyer, Thomas Oudman, Mariana Villalba
Mini-talk + poster
Mini-talk + poster
Mini-talk + poster
In recent years it has become increasingly apparent that non-genetic forms of heredity exist in a wide variety of organisms. Furthermore, these “extended” forms of heredity can have interesting and important effects on how evolution by natural selection proceeds. Parallel to these findings has been the development of ideas from evo-devo, niche construction theory, and theory related to other “constructive” processes in evolution, with many of the researchers involved now calling for a revision or extension of the Modern Synthesis of Evolutionary Biology. In this talk I will give my own view of these issues by attempting to put all of the recent arguments within a common theoretical perspective. My goal in doing so is to clarify what both sides of the debate are saying so that a more productive dialogue can be had.