Group Selection and Group Adaptation During a Major Evolutionary Transition: Insights from the Evolution of Multicellularity in the Volvocine Algae

Shelton, Deborah E.; Michod, Richard E.

doi:10.1007/s13752-014-0159-x

Cited by 39 publications

(64 citation statements)

References 37 publications

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“…Any trait that is costly at the lower level but beneficial at the group level enhances the fitness of the group at the expense of lower-level fitness and may therefore contribute to fitness decoupling and the emergence of indivisibility of the group. In addition, traits that evolve in the context of the group may no longer be optimal were cells to leave the group (Shelton and Michod 2014). This context-dependent evolution increases the fitness of the group and decreases the fitness of cells were they to leave the group.…”

Section: Reproductive Division Of Labormentioning

confidence: 99%

“…A group is indivisible if lower-level units cannot leave the group, potentially because of a colony boundary. Indivisibility may also arise when cells possess properties in the context of the group that would make them less fit were they to leave the group (Shelton and Michod 2014). Huxley (1932) considered individuality to be characterized by autonomy and physiological unity (Table 1), which imply that the individual interacts as a whole with the external environment.…”

Section: Indivisibilitymentioning

confidence: 99%

“…The presence of group-level adaptations is another criterion for individuality (Vrba 1984;Folse and Roughgarden 2010;Shelton and Michod 2014).This criterion captures the expected outcome of Darwinian evolution at the group level (Lewontin 1970). The criterion of grouplevel adaptations specifically excludes cross-level byproducts, which occur when lower-level and group-level traits covary resulting in apparent selection at the group level (Okasha 2006).…”

Section: Group-level Adaptationsmentioning

confidence: 99%

“…Determining whether group properties are aggregative or emergent properties of cells and understanding the relationship between group-level traits and fitness at the cell and group levels may help identify group-level adaptations (Damuth and Heisler 1988;Lloyd and Gould 1993;Wimsatt 1997). Shelton and Michod (2014) have proposed testable predictions, based on an explicit mathematical model, which help to determine whether traits are group-level adaptations including strong group-level fitness effects.…”

Section: Group-level Adaptationsmentioning

confidence: 99%

“…Alternatively, the secretion of extracellular matrix may be a cell-level adaptation which increases the inclusive fitness of secreting cells. Shelton and Michod (2014) analyzed a model of simple clusters of genetically identical cells as a way to understand when group-level adaptations emerge. The conditions under which group adaptations emerge depend on how strongly group membership affects life history variables such as mortality and growth.…”

Section: Chlamydomonasmentioning

confidence: 99%

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Evolution of Individuality: A Case Study in the Volvocine Green Algae

Hanschen¹,

Davison²,

Grochau-Wright³

et al. 2017

Philosophy, Theory, and Practice in Biology

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While numerous criteria have been proposed in definitions of biological individuality, it is not clear whether these criteria reflect the evolutionary processes that underlie transitions in individuality. We consider the evolution of individuality during the transition from unicellular to multicellular life. We assume that "individuality" (however it is defined) has changed in the volvocine green algae lineage during the transition from single cells, to simple multicellular colonies with four to one hundred cells, to more complex multicellular organisms with thousands of differentiated cells. We map traits associated with the various proposed individuality criteria onto volvocine algae species thought to be similar to ancestral forms arising during this transition in individuality. We find that the fulfillment of some criteria, such as genetic homogeneity and genetic uniqueness, do not change across species, while traits underpinning other aspects of individuality, including degrees of integration, group-level fitness and adaptation, and group indivisibility, change dramatically. We observe that different kinds of individuals likely exist at different levels of organization (cell and group) in the same species of algae. Future research should focus on the causes and consequences of variation in individuality.

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Section: Reproductive Division Of Labormentioning

confidence: 99%

Section: Indivisibilitymentioning

confidence: 99%

Section: Group-level Adaptationsmentioning

confidence: 99%

Section: Group-level Adaptationsmentioning

confidence: 99%

Section: Chlamydomonasmentioning

confidence: 99%

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Evolution of Individuality: A Case Study in the Volvocine Green Algae

Hanschen¹,

Davison²,

Grochau-Wright³

et al. 2017

Philosophy, Theory, and Practice in Biology

Self Cite

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Germ lines and extended selection during the evolutionary transition to multicellularity

Rose

2020

J Exp Zool Pt B

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The major evolutionary transitions from unicellular organisms to multicellularity resulted in a profusion of complex life forms. During the transition from single cells to multicellular life, groups of cells acquired the capacity for reproduction as discrete units; however, the selective causes and underlying mechanisms remain debated. One perspective views the evolution of multicellularity as a shift in the timescale at which natural selection primarily operates—from that of individual cells to the timescale of reproducing groups of cells. Therefore, a distinguishing feature of multicellular reproduction, as opposed to simple growth of a multicellular collective, is that the capacity for reproduction must develop over a timescale that is greater than the reproductive timescale of a single cell. Here, I suggest that the emergence of specialized reproductive cells (the germ line) was an essential first stage of the evolutionary transition to multicellularity because it imposed the necessary “delay”—allowing natural selection to operate over the longer timescale of a multicellular life cycle, ultimately resulting in the evolution of complex multicellular organisms. This perspective highlights the possibility that the ubiquity of a germ–soma distinction among complex multicellular organisms reflects the fact that such life cycles, on first emergence, had the greatest propensity to participate in Darwinian evolution.

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