A way forward with eco evo devo: an extended theory of resource polymorphism with postglacial fishes as model systems (original) (raw)
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Developmental rate: A unifying mechanism for sympatric divergence in postglacial fishes
Morphologically divergent ecotypes arise in fish populations on postglacial time scales, and resource polymorphisms are often invoked to explain their origin. However, genetic recombination can constrain the ability of divergent selection to produce reproductive isolation in sympatry. Recombination breaks up favorable combinations of traits ("adaptive suites") if individual traits are affected by different loci. Recombination also breaks up any association between traits under divergent selection and traits contributing to reproductive isolation. Thus, ecological speciation in the absence of preexisting barriers to gene flow is more likely when pleiotropy minimizes the number of loci involved. Here, we revisit research conducted by Carl Hubbs in the early 1900s on the effects of developmental rate on morphological traits in fishes. Hubbs' work provides a mechanism to explain how sympatric divergence by trophic polymorphism can occur despite the challenges of recombination. We consider the implications of Hubbs' observations for ecological speciation with gene flow in fishes, as well as rapid evolution in captive fish populations [Current Zoology 58 (1): 21-34, 2012].
Resource trait specialisation in an introduced fish population with reduced genetic diversity
Biological Invasions, 2020
Ecological specialisation is hypothesised to play a major role in the evolution of phenotypic diversity, especially following the colonisation of novel habitats. For example, cichlid fishes provide some of the most remarkable evidence for rapid ecological diversification. Here, we capitalised on a recently (≤40 years ago) introduced population of red devils (Amphilophus labiatus) in Australia, to investigate adaptive phenotypic responses to a novel environment. We used stomach content analyses, morphometrics and laboratory experiments to test for covariation between diet and size of an important trophic trait, lip size. We found that, while maximum lip size in the study population was smaller than in the species' natural range, the proportions of algae, insects and fish remains in the diet covaried with lip size. However, contrary to predictions, we found no evidence for lip development to be plastic under laboratory conditions in relation to substrate complexity or food manipulation, nor did we find any relationship between lip morphology and feeding performance in adults. Single nucleotide polymorphism data, in turn, suggested that the introduced population has reduced standing genetic variation, which potentially influences both phenotypic plasticity and diversity, in comparison to native populations. Together, the results suggest that morphological variation in a key trophic trait can respond rapidly to diet in a novel environment, despite reduced genetic diversity in the population.
EVOLUTIONARY SIGNIFICANCE OF RESOURCE POLYMORPHISMS IN FISHES, AMPHIBIANS, AND BIRDS
Annual Review of Ecology and Systematics, 1996
Resource polymorphism in vertebrates is generally underappreciated as a diversifying force and is probably more common than is currently recognized. Research across diverse taxa suggest they may play important roles in population divergence and speciation. They may involve various kinds of traits, including morphological and behavioral traits and those related to life history. Many of the evolutionary, ecological, and genetic mechanisms producing and maintaining resource polymorphisms are similar among phylogenetically distinct species. Although further studies are needed, the genetic basis may be simple, in some cases under the control of a single locus, with phenotypic plasticity playing a proximate role in some taxa. Divergent selection including either directional, disruptive, or frequencydependent selection is important in their evolution. Generally, the invasion of "open" niches or underutilized resources requiring unique trophic characters and decreased interspecific competition have promoted the evolution of resource polymorphisms. Further investigations centered on their role in speciation, especially adaptive radiation, are likely to be fruitful. Annu. Rev. Ecol. Syst. 1996.27:111-133. Downloaded from arjournals.annualreviews.org by University of Texas, Austin on 07/05/05. For personal use only. RESOURCE POLYMORPHISMS 113 shape, and in life history characteristics (e.g. 49, 66, 68, 69, 105, 122, 125, 147,. In some cases resource segregation is clear and stable, such as between benthic and limnetic habitats (79, 135), while in other cases, habitat and food segregation are less dramatic and often seasonal (57, 125,.
Ecological genetics of freshwater fish: a short review of the genotype–phenotype connection
Animal Biodiversity and Conservation
Molecular ecology or ecological genetics is an expanding application of population genetics which has flourished in the last two decades but it is dominated by systematic and phylogeographic studies, with relatively little emphasis on the study of the genetic basis of the process of adaptation to different ecological conditions. The relationship between genotype and adaptive phenotypes is weak because populations are often difficult to quantify and experiments are logistically challenging or unfeasible. Interestingly, in freshwater fish, studies to characterize the genetic architecture of adaptive traits are not as rare as in other vertebrate groups. In this review, we summarize the few cases where the relationship between the ecology and genetics of freshwater fish is more developed, namely the relationship between genetic markers and ecological phenotypes.
Hydrobiologia, 1995
In most types of freshwater ecosystems fish diversity depends greatly on land/inland water ecotones. So, to maintain biodiversity of fish communities in inland waters, management and restoration of aquatic terrestrial ecotones will be an important tool. However, to provide a scientific background for such conservation activities, it will be desirable to test the importance of different types of ecotones in structuring and maintaining the genetic diversity of fish populations. The relevance of population genetics data to ecotone studies can only be understood in an ecological context as evolution is a function of environment. We suggest that as ecotone complexity increases opportunities for survival of individuals, improving trophic conditions and spatial habitat heterogeneity, so the population size and variation increase with increased genetic diversity and vulnerability to environment changes decreases .
The consequences of genomic architecture on ecological speciation in postglacial fishes
Current Zoology, 2013
The quest for the origin of species has entered the genomics era. Despite decades of evidence confirming the role of the environment in ecological speciation, an understanding of the genomics of ecological speciation is still in its infancy. In this review, we explore the role of genomic architecture in ecological speciation in postglacial fishes. Growing evidence for the number, location, effect size, and interactions among the genes underlying population persistence, adaptive trait divergence, and reproductive isolation in these fishes reinforces the importance of considering genomic architecture in studies of ecological speci-ation. Additionally, these populations likely adapt to new freshwater environments by selection on standing genetic variation, as de novo mutations are unlikely under such recent divergence times. We hypothesize that modular genomic architectures in postglacial fish taxa may be associated with the probability of population persistence. Empirical studies have...
Organisms are niche constructors: they impact the environment and modify selective pressures that direct their own evolution as well as that of their non-conspecific fellows in ecological systems at various scales. The theoretical acknowledgement of niche construction has inspired many reflections about the active role of organisms in evolution, often proclaiming a revolutionary theoretical change. But if we look at formal models the claim is not yet justified. Ecologists have specified population-scale models of niche construction, but these cannot be adopted as evolutionary models: they don't incorporate heritable variation nor allow for directional selection and cumulative change. As evolutionists point out, these models are mere phenotype dynamics or population fluctuations with different possible outcomes - extinction or sustainability. Evolutionary models of niche construction, on the other hand, are not so revolutionary in their foundations, often being just classical population genetics provided with feedback loops between loci and selective pressures acting on them. The idea that variation among organisms boils down to genetic differences captured by gene frequencies dates back to the heart of the Modern Synthesis. But niche construction points directly to the world of physical and chemical interactions. This is the world where resource-impacting phenotypes are built through developmental processes, in turn subject and sensitive to the surrounding environment and the resources left over by previous generations. The produced phenotypes and their effects are hardly summarized by gene frequencies, yet evolutionary models need some kind of heritable variation and selection. The future challenge of evolutionary modeling beyond the Modern Synthesis is thus ecological, plastic variation that allows for inheritance with varying degrees and not-always-allelic mechanisms.
Evolution, 2011
In addition to the well-studied evolutionary parameters of (1) phenotype-fitness covariance and (2) the genetic basis of phenotypic variation, adaptive evolution by natural selection requires that (3) fitness variation is effected by heritable genetic differences among individuals and (4) phenotype-fitness covariances must be, at least in part, underlain by genetic covariances. These latter two requirements for adaptive evolutionary change are relatively unstudied in natural populations. Absence of the latter requirements could explain stasis of apparently directionally selected heritable traits. We provide complementary analyses of selection and variation at phenotypic and genetic levels for juvenile growth rate in brook charr Salvelinus fontinalis in Freshwater River, Newfoundland, Canada. Contrary to the vast majority of reports in fish, we found very little viability selection of juvenile body size. Large body size appears nonetheless to be selectively advantageous via a relationship with early maturity. Genetic patterns in evolutionary parameters largely reflected phenotypic patterns. We have provided inference of selection based on longitudinal data, which are uncommon in high fecundity organisms. Furthermore we have provided a practicable framework for further studies of the genetic basis of natural selection.