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  • 1.
    Andersson, Rebecka
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik.
    Isaksson, Hanna
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik.
    Libby, Eric
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik. Santa Fe Institute, NM, Santa Fe, USA.
    Multi-species multicellular life cycles2022Ingår i: The evolution of multicellularity, CRC Press, 2022, s. 343-356Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    Textbook examples of multicellular organisms vary in their scale and complexity but are typically composed of a single species. The prevalence of entities such as lichens, however, suggest that two different species may be capable of forming a type of multi-species multicellularity-though it may not resemble its clonal counterparts. In this chapter, we consider the possibility of multi-species multicellularity and in particular its origins. Drawing upon previous studies of the evolutionary origins of clonal multicellularity, we focus on the emergence of simple reproducing groups that have the capacity to gain adaptations. We present a framework for organizing these initial multi-species group life cycles based on whether the constituent species are unicellular or multicellular and whether the groups reproduce via fragmentation or cycles of dissociation and re-association. We discuss characteristics of each type of multi-species multicellularity and representative examples to assess their likely evolutionary trajectories. Ultimately, we conclude that the multi-species groups that most resemble textbook multicellular organisms are composed of unicellular and multicellular species and reproduce via cycles of dissociation and re-association.

  • 2.
    Isaksson, Hanna
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik.
    Brännström, Åke
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik. Advancing Systems Analysis Program, International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria; Complexity Science and Evolution Unit, Okinawa Institute of Science and Technology Graduate University, Japan.
    Libby, Eric
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik.
    Minor variations in multicellular life cycles have major effects on adaptation2023Ingår i: PloS Computational Biology, ISSN 1553-734X, E-ISSN 1553-7358, Vol. 19, nr 4, artikel-id e1010698Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Multicellularity has evolved several independent times over the past hundreds of millions of years and given rise to a wide diversity of complex life. Recent studies have found that large differences in the fundamental structure of early multicellular life cycles can affect fitness and influence multicellular adaptation. Yet, there is an underlying assumption that at some scale or categorization multicellular life cycles are similar in terms of their adaptive potential. Here, we consider this possibility by exploring adaptation in a class of simple multicellular life cycles of filamentous organisms that only differ in one respect, how many daughter filaments are produced. We use mathematical models and evolutionary simulations to show that despite the similarities, qualitatively different mutations fix. In particular, we find that mutations with a tradeoff between cell growth and group survival, i.e. "selfish" or "altruistic" traits, spread differently. Specifically, altruistic mutations more readily spread in life cycles that produce few daughters while in life cycles producing many daughters either type of mutation can spread depending on the environment. Our results show that subtle changes in multicellular life cycles can fundamentally alter adaptation.

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  • 3.
    Isaksson, Hanna
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik. Integrated Science Lab, Umeå University, Umeå, Sweden.
    Conlin, Peter L.
    Georgia Institute of Technology, School of Biological Sciences, GA, Atlanta, United States.
    Kerr, Ben
    BEACON Center for the Study of Evolution in Action, Department of Biology, University of Washington, WA, Seattle, United States.
    Ratcliff, William C.
    Georgia Institute of Technology, School of Biological Sciences, GA, Atlanta, United States.
    Libby, Eric
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik. Integrated Science lab, Umeå University, Umeå, Sweden; Santa Fe Institute, NM, Santa Fe, United States.
    The consequences of budding versus binary fission on adaptation and aging in primitive multicellularity2021Ingår i: Genes, ISSN 2073-4425, E-ISSN 2073-4425, Vol. 12, nr 5, artikel-id 661Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Early multicellular organisms must gain adaptations to outcompete their unicellular ancestors, as well as other multicellular lineages. The tempo and mode of multicellular adaptation is influenced by many factors including the traits of individual cells. We consider how a fundamental aspect of cells, whether they reproduce via binary fission or budding, can affect the rate of adaptation in primitive multicellularity. We use mathematical models to study the spread of beneficial, growth rate mutations in unicellular populations and populations of multicellular filaments reproducing via binary fission or budding. Comparing populations once they reach carrying capacity, we find that the spread of mutations in multicellular budding populations is qualitatively distinct from the other populations and in general slower. Since budding and binary fission distribute age-accumulated damage differently, we consider the effects of cellular senescence. When growth rate decreases with cell age, we find that beneficial mutations can spread significantly faster in a multicellular budding population than its corresponding unicellular population or a population reproducing via binary fission. Our results demonstrate that basic aspects of the cell cycle can give rise to different rates of adaptation in multicellular organisms.

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  • 4.
    Isaksson, Hanna
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik.
    Lind, Peter A
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Libby, Eric
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik. Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Adaptive evolutionary trajectories in complexity: repeated transitions between unicellularity and differentiated multicellularityManuskript (preprint) (Övrigt vetenskapligt)
  • 5.
    Isaksson, Hanna
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik.
    Ratcliff, William
    Georgia Institute of Technology, School of Biological Sciences, GA, Atlanta, United States..
    Libby, Eric
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik.
    Cell-level information and the evolution of regulated multicellular life cyclesManuskript (preprint) (Övrigt vetenskapligt)
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