Browsing by Subject "natural selection"

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  • Fleming, R.A. (The Finnish Society of Forest Science and The Finnish Forest Research Institute, 1996)
    There is no doubt that tree survival, growth, and reproduction in North America’s boreal forest would be directly influenced by the projected changes in climate if they occur. The indirect effects of climate change may be of even greater importance, however, because of their potential for altering the intensity, frequency, and perhaps even the very nature of the disturbance regimes which drive boreal forest dynamics. Insect defoliator populations are one of the dominating disturbance factors in North America’s boreal forests and during outbreaks trees are often killed over vast forest areas. If the predicted shifts in climate occur, the damage patterns caused by insects may be considerably changed, particularly those of insects whose temporal and spatial distributions are singularly dependent on climatic factors. The ensuing uncertainties directly affect depletion forecasts, pest hazard rating procedures, and long-term planning for pest control requirements. Because the potential for wildfire often increases in stands after insect attack, uncertainties in future insect damage patterns also lead to uncertainties in fire regimes. In addition, because the rates of processes key to biogeochemical and nutrient recycling are influenced by insect damage, potential changes in damage patterns can indirectly affect ecosystem resilience and the sustainability of the multiple uses of the forest resource. In this paper, a mechanistic perspective is developed based on available information describing how defoliatoring forest insects might respond to climate warming. Because of its prevalence and long history of study, the spruce budworm, Choristoneura fumiferana Clem. (Lepidoptera: Tortricidae), is used for illustrative purposes in developing this perspective. The scenarios that follow outline the potential importance of threshold behavior, historical conditions, phenological relationships, infrequent but extreme weather, complex feedbacks, and natural selection. The urgency of such considerations is emphasized by reference to research suggesting that climate warming may already be influencing some insect lifecycles.
  • Coronado-Zamora, Marta; Salvador-Martinez, Irepan; Castellano, David; Barbadilla, Antonio; Salazar-Ciudad, Isaac (2019)
    Previous studies of the evolution of genes expressed at different life-cycle stages of Drosophila melanogaster have not been able to disentangle adaptive from nonadaptive substitutions when using nonsynonymous sites. Here, we overcome this limitation by combining whole-genome polymorphism data from D. melanogaster and divergence data between D. melanogaster and Drosophila yakuba. For the set of genes expressed at different life-cycle stages of D. melanogaster, as reported in modENCODE, we estimate the ratio of substitutions relative to polymorphism between nonsynonymous and synonymous sites (alpha) and then alpha is discomposed into the ratio of adaptive (omega(a)) and nonadaptive (omega(na)) substitutions to synonymous substitutions. We find that the genes expressed in mid- and late-embryonic development are the most conserved, whereas those expressed in early development and postembryonic stages are the least conserved. Importantly, we found that low conservation in early development is due to high rates of nonadaptive substitutions (high omega(na)), whereas in postembryonic stages it is due, instead, to high rates of adaptive substitutions (high omega(a)). By using estimates of different genomic features (codon bias, average intron length, exon number, recombination rate, among others), we also find that genes expressed in mid- and late-embryonic development show the most complex architecture: they are larger, have more exons, more transcripts, and longer introns. In addition, these genes are broadly expressed among all stages. We suggest that all these genomic features are related to the conservation of mid- and late-embryonic development. Globally, our study supports the hourglass pattern of conservation and adaptation over the life-cycle.
  • Qvarnstrom, Anna; Alund, Murielle; McFarlane, S. Eryn; Sirkiä, Päivi (2016)
    Climate adaptation is surprisingly rarely reported as a cause for the build-up of reproductive isolation between diverging populations. In this review, we summarize evidence for effects of climate adaptation on pre- and postzygotic isolation between emerging species with a particular focus on pied (Ficedula hypoleuca) and collared (Ficedula albicollis) flycatchers as a model for research on speciation. Effects of climate adaptation on prezygotic isolation or extrinsic selection against hybrids have been documented in several taxa, but the combined action of climate adaptation and sexual selection is particularly well explored in Ficedula flycatchers. There is a general lack of evidence for divergent climate adaptation causing intrinsic postzygotic isolation. However, we argue that the profound effects of divergence in climate adaptation on the whole biochemical machinery of organisms and hence many underlying genes should increase the likelihood of genetic incompatibilities arising as side effects. Fast temperature-dependent co-evolution between mitochondrial and nuclear genomes may be particularly likely to lead to hybrid sterility. Thus, how climate adaptation relates to reproductive isolation is best explored in relation to fast-evolving barriers to gene flow, while more research on later stages of divergence is needed to achieve a complete understanding of climate-driven speciation.
  • Annila, Arto; Salthe, Stanley (2010)
  • Vatka, Emma; Orell, Markku; Rytkönen, Seppo; Merilä, Juha (2021)
    Many populations need to adapt to changing environmental conditions, such as warming climate. Changing conditions generate directional selection for traits critical for fitness. For evolutionary responses to occur, these traits need to be heritable. However, changes in environmental conditions can alter the amount of heritable variation a population expresses, making predictions about expected responses difficult. The aim of this study was to evaluate the effects of ambient temperatures on evolutionary potential and strength of natural selection on the timing of reproduction in two passerine birds breeding in boreal forests. Long-term data on individually marked Willow Tits Poecile montanus (1975-2018) and Great Tits Parus major (1969-2018) were analysed with random regression animal models to assess if spring temperatures affect the expressed amount of additive genetic variation (V-A) and heritability (h(2)) in the timing of breeding. We assessed if ambient temperatures of different seasons influenced the direction and strength of selection on breeding time. We also evaluated if the strength of selection covaried with evolutionary potential. Levels of V-A or h(2) expressed in laying date were unaffected by spring temperatures in both study species. Selection for earlier breeding was found in the Willow Tit, but not in the Great Tit. In the Willow Tit, selection for earlier breeding was more intense when the temperatures of following autumns and winters were low. Different measures of evolutionary potential did not covary strongly with the strength of selection in either species. We conclude that there is no or little evidence that climate warming would either constrain or promote evolutionary potential in timing of breeding through changes in amount of genetic variance expressed in boreal Willow and Great Tits. However, selection on the timing of breeding, a life-history event taking place in springtime, is regulated by temperatures of autumns and winters. Rapid warming of these periods have thus potential to reduce the rate of expected evolutionary response in reproductive timing.
  • Gonda, Maria Abigel; Herczeg, Gabor; Merilä, Juha (2013)
  • De-la-Cruz, Ivan M.; Batsleer, Femke; Bonte, Dries; Diller, Carolina; Hytönen, Timo; Muola, Anne; Osorio, Sonia; Posé, David; Vandegehuchte, Martijn L.; Stenberg, Johan A. (2022)
    Aboveground plant-arthropod interactions are typically complex, involving herbivores, predators, pollinators, and various other guilds that can strongly affect plant fitness, directly or indirectly, and individually, synergistically, or antagonistically. However, little is known about how ongoing natural selection by these interacting guilds shapes the evolution of plants, i.e., how they affect the differential survival and reproduction of genotypes due to differences in phenotypes in an environment. Recent technological advances, including next-generation sequencing, metabolomics, and gene-editing technologies along with traditional experimental approaches (e.g., quantitative genetics experiments), have enabled far more comprehensive exploration of the genes and traits involved in complex ecological interactions. Connecting different levels of biological organization (genes to communities) will enhance the understanding of evolutionary interactions in complex communities, but this requires a multidisciplinary approach. Here, we review traditional and modern methods and concepts, then highlight future avenues for studying the evolution of plant-arthropod interactions (e.g., plant-herbivore-pollinator interactions). Besides promoting a fundamental understanding of plant-associated arthropod communities’ genetic background and evolution, such knowledge can also help address many current global environmental challenges.
  • Opedal, Oystein H.; Gross, Karin; Chapurlat, Elodie; Parachnowitsch, Amy; Joffard, Nina; Sletvold, Nina; Ovaskainen, Otso; Friberg, Magne (2022)
    Natural selection on floral scent composition is a key element of the hypothesis that pollinators and other floral visitors drive scent evolution. The measure of such selection is complicated by the high-dimensional nature of floral scent data and uncertainty about the cognitive processes involved in scent-mediated communication. We use dimension reduction through reduced-rank regression to jointly estimate a scent composite trait under selection and the strength of selection acting on this trait. To assess and compare variation in selection on scent across species, time and space, we reanalyse 22 datasets on six species from four previous studies. The results agreed qualitatively with previous analyses in terms of identifying populations and scent compounds subject to stronger selection but also allowed us to evaluate and compare the strength of selection on scent across studies. Doing so revealed that selection on floral scent was highly variable, and overall about as common and as strong as selection on other phenotypic traits involved in pollinator attraction or pollen transfer. These results are consistent with an important role of floral scent in pollinator attraction. Our approach should be useful for further studies of plant-animal communication and for studies of selection on other high-dimensional phenotypes. In particular, our approach will be useful for studies of pollinator-mediated selection on complex scent blends comprising many volatiles, and when no prior information on the physiological responses of pollinators to scent compounds is available.
  • Brommer, Jon E.; Kontiainen, Pekka; Pietiäinen, Hannu (2012)
  • Ramirez-Valiente, Jose Alberto; Sole-Medina, Aida; Pyhäjärvi, Tanja; Cervantes, Sandra; Kesalahti, Robert; Kujala, Sonja T.; Kumpula, Timo; Heer, Katrin; Opgenoorth, Lars; Siebertz, Jan; Danusevicius, Darius; Notivol, Eduardo; Benavides, Raquel; Robledo-Arnuncio, Juan Jose (2021)
    Understanding the dynamics of selection is key to predicting the response of tree species to new environmental conditions in the current context of climate change. However, selection patterns acting on early recruitment stages and their climatic drivers remain largely unknown in most tree species, despite being a critical period of their life cycle. We measured phenotypic selection on Pinus sylvestris seed mass, emergence time and early growth rate over 2 yr in four common garden experiments established along the latitudinal gradient of the species in Europe. Significant phenotypic plasticity and among-population genetic variation were found for all measured phenotypic traits. Heat and drought negatively affected fitness in the southern sites, but heavy rainfalls also decreased early survival in middle latitudes. Climate-driven directional selection was found for higher seed mass and earlier emergence time, while the form of selection on seedling growth rates differed among sites and populations. Evidence of adaptive and maladaptive phenotypic plasticity was found for emergence time and early growth rate, respectively. Seed mass, emergence time and early growth rate have an adaptive role in the early stages of P. sylvestris and climate strongly influences the patterns of selection on these fitness-related traits.
  • Annila, Arto (2021)
    Evolution is customarily perceived as a biological process. However, when formulated in terms of physics, evolution is understood to entail everything. Based on the axiom of everything comprising quanta of actions (e.g., quanta of light), statistical physics describes any system evolving toward thermodynamic balance with its surroundings systems. Fluxes of quanta naturally select those processes leveling out differences in energy as soon as possible. This least-time maxim results in ubiquitous patterns (i.e., power laws, approximating sigmoidal cumulative curves of skewed distributions, oscillations, and even the regularity of chaos). While the equation of evolution can be written exactly, it cannot be solved exactly. Variables are inseparable since motions consume driving forces that affect motions (and so on). Thus, evolution is inherently a non-deterministic process. Yet, the future is not all arbitrary but teleological, the final cause being the least-time free energy consumption itself. Eventually, trajectories are computable when the system has evolved into a state of balance where free energy is used up altogether.
  • Annila, Arto; Keto, Jaana (2012)
    The on-going whole genome sequencing and whole cell assays of metabolites and proteins imply that complex systems could ultimately be mastered by perfecting knowledge into great detail. However, courses of nature are inherently intractable because flows of energy and their driving forces depend on each other. Thus no data will suffice to predict precisely the outcomes of e.g., engineering experiments. All path-dependent processes, most notably evolution in its entirety, display this capricious character of nature.
  • Annila, Arto (2021)
    About a century ago, in the spirit of ancient atomism, the quantum of light was renamed the photon to suggest that it is the fundamental element of everything. Since the photon carries energy in its period of time, a flux of photons inexorably embodies a flow of time. Thus, time comprises periods as a trek comprises legs. The flows of quanta naturally select optimal paths (i.e., geodesics) to level out energy differences in the least amount of time. The corresponding flow equations can be written, but they cannot be solved. Since the flows affect their driving forces, affecting the flows, and so on, the forces (i.e., causes) and changes in motions (i.e., consequences) are inseparable. Thus, the future remains unpredictable. However, it is not all arbitrary but rather bounded by free energy. Eventually, when the system has attained a stationary state where forces tally, there are no causes and no consequences. Since there are no energy differences between the system and its surroundings, the quanta only orbit on and on. Thus, time does not move forward either but circulates.
  • Wei, Shichao; Li, Zitong; Momigliano, Paolo; Fu, Chao; Wu, Hua; Merilä, Juha (2020)
    The role of geological events and Pleistocene climatic fluctuations as drivers of current patterns of genetic variation in extant species has been a topic of continued interest among evolutionary biologists. Nevertheless, comprehensive studies of widely distributed species are still rare, especially from Asia. Using geographically extensive sampling of many individuals and a large number of nuclear single nucleotide polymorphisms (SNPs), we studied the phylogeography and historical demography ofHyla annectanspopulations in southern China. Thirty-five sampled populations were grouped into seven clearly defined genetic clusters that closely match phenotype-based subspecies classification. These lineages diverged 2.32-5.23 million years ago (Ma), a timing that closely aligns with the rapid and drastic uplifting of the Qinghai-Tibet Plateau and adjacent southwest China. Demographic analyses and species distribution models indicate that different populations of this species have responded differently to past climatic changes. In the Hengduan Mountains, most populations experienced a bottleneck, whereas the populations located outside of the Hengduan Mountains have gradually declined in size since the end of the last glaciation. In addition, the levels of phenotypic and genetic divergence were strongly correlated across major clades. These results highlight the combined effects of geological events and past climatic fluctuations, as well as natural selection, as drivers of contemporary patterns of genetic and phenotypic variation in a widely distributed anuran in Asia.
  • Opedal, Øystein H.; Hegland, Stein Joar (2020)
    1. Pollinator-mediated reproductive interactions among co-flowering plant species are prime examples of how species interactions may affect fitness and community assembly. Despite considerable interest in these issues, statistical methods for assessing signal of reproductive interactions in observational data on co-flowering species are currently lacking. 2. We propose a flexible method for quantifying potential reproductive interactions among co-flowering plant species using the hierarchical latent-variable joint models implemented in the Hierarchical Modelling of Species Communities (HMSC) framework. The method accommodates any measure of reproductive success, including pollinator visitation, stigma pollen loads, and seed set. We demonstrate the method by analysing a dataset on bumblebee visitation to a set of co-flowering plant species in a species-rich meadow in Norway, and provide R tutorials for this and additional data types. 3. The example analysis revealed both positive and negative effects of heterospecific flower abundances on visitation to co-flowering species, which we interpret as potential reproductive interactions. 4. Synthesis. Hierarchical joint models provide a flexible approach to analysing patterns of covariation in the reproductive success of co-flowering species, thus identifying potential species interactions. Important strengths include explicit consideration of community-level effects and the assessment of residual fitness correlations after controlling for covariates such as flower abundances and phenotypic traits, yielding more complete insights into pollinator-mediated reproductive interactions.