scholarly journals Geometry shapes evolution of early multicellularity

2014 ◽  
Author(s):  
Eric Libby ◽  
Will Ratcliff ◽  
Mike Travisano ◽  
Ben Kerr
Keyword(s):  
Cell Death ◽  
Division Of Labor ◽  
Cell Number ◽  
Evolutionary Transition ◽  
Yeast Saccharomyces Cerevisiae ◽  
Evolutionary Transitions ◽  
Major Transitions ◽  
Reproductive Differentiation ◽  
Reproductive Division Of Labor ◽  
Reproductive Division

Organisms have increased in complexity through a series of major evolutionary transitions, in which formerly autonomous entities become parts of a novel higher-level entity. One intriguing feature of the higher-level entity after some major transitions is a division of reproductive labor among its lower-level units. Although it can have clear benefits once established, it is unknown how such reproductive division of labor originates. We consider a recent evolution experiment on the yeast Saccharomyces cerevisiae as a unique platform to address the issue of reproductive differentiation during an evolutionary transition in individuality. In the experiment, independent yeast lineages evolved a multicellular “snowflake-like” cluster form in response to gravity selection. Shortly after the evolution of clusters, the yeast evolved higher rates of cell death. While cell death enables clusters to split apart and form new groups, it also reduces their performance in the face of gravity selection. To understand the selective value of increased cell death, we create a mathematical model of the cellular arrangement within snowflake yeast clusters. The model reveals that the mechanism of cell death and the geometry of the snowflake interact in complex, evolutionarily important ways. We find that the organization of snowflake yeast imposes powerful limitations on the available space for new cell growth. By dying more frequently, cells in clusters avoid encountering space limitations, and, paradoxically, reach higher numbers. In addition, selection for particular group sizes can explain the increased rate of apoptosis both in terms of total cell number and total numbers of collectives. Thus, by considering the geometry of a primitive multicellular organism we can gain insight into the initial emergence of reproductive division of labor during an evolutionary transition in individuality.

scholarly journals Division of labor and fitness decoupling in evolutionary transitions in individuality

2020 ◽  
Author(s):  
Guilhem Doulcier ◽  
Katrin Hammerschmidt ◽  
Pierrick Bourrat
Keyword(s):  
Division Of Labor ◽  
Life History Traits ◽  
Linear Functions ◽  
Evolutionary Constraints ◽  
Evolutionary Transitions ◽  
Evolutionary Transitions In Individuality ◽  
Reproductive Division Of Labor ◽  
Multicellular Organisms ◽  
Reproductive Division

AbstractReproductive division of labor has been proposed to play a key role for evolutionary transitions in individuality (ETIs). This chapter provides a guide to a theoretical model that addresses the role of a tradeoff between life-history traits in selecting for a reproductive division of labor during the transition from unicellular to multicellular organisms. In particular, it focuses on the five keys assumptions of the model, namely (1) fitness is viability times fecundity; (2) collective traits are linear functions of their cellular counterparts; (3) there is a tradeoff between cell viability and fecundity; (4) cell contribution to the collective is optimal; and (5) there is an initial reproductive cost in large collectives. Thereafter the chapter contrasts two interpretations of the model in the context of ETIs. Originally, the model was interpreted as showing that during the transition to multicellularity the fitness of the lower-level (the cells) is “transferred” to the higher level (the collective). Despite its apparent intuitiveness, fitness transfer may obscure actual mechanisms in metaphorical language. Thus, an alternative and more conservative interpretation of the model that focuses on cell traits and the evolutionary constraints that links them is advocated. In addition, it allows for pursuing subsequent questions, such as the evolution of development.

scholarly journals Morphological and genomic shifts in mole-rat ‘queens’ increase fecundity but reduce skeletal integrity

2020 ◽  
Author(s):  
Rachel A. Johnston ◽  
Philippe Vullioud ◽  
Jack Thorley ◽  
Henry Kirveslahti ◽  
Leyao Shen ◽  
...  
Keyword(s):  
Division Of Labor ◽  
Morphological Plasticity ◽  
Skeletal Morphology ◽  
Eusocial Insects ◽  
Mole Rat ◽  
Gene Regulatory ◽  
Reproductive Division Of Labor ◽  
Reproductive Division ◽  
Skeletal Integrity ◽  
Vertebral Growth

AbstractIn some mammals and many social insects, highly cooperative societies are characterized by reproductive division of labor, in which breeders and nonbreeders become behaviorally and morphologically distinct. While differences in behavior and growth between breeders and nonbreeders have been extensively described, little is known of their molecular underpinnings. Here, we investigate the consequences of breeding for skeletal morphology and gene regulation in highly cooperative Damaraland mole-rats. By experimentally assigning breeding ‘queen’ status versus nonbreeder status to age-matched littermates, we confirm that queens experience vertebral growth that likely confers advantages to fecundity. However, they also up-regulate bone resorption pathways and show reductions in femoral mass, which predicts increased vulnerability to fracture. Together, our results show that, as in eusocial insects, reproductive division of labor in mole-rats leads to gene regulatory rewiring and extensive morphological plasticity. However, in mole-rats, concentrated reproduction is also accompanied by costs to bone strength.

scholarly journals The order of trait emergence in the evolution of cyanobacterial multicellularity

2019 ◽  
Author(s):  
Katrin Hammerschmidt ◽  
Giddy Landan ◽  
Fernando Domingues Kümmel Tria ◽  
Jaime Alcorta ◽  
Tal Dagan
Keyword(s):  
Division Of Labor ◽  
Phenotypic Trait ◽  
Evolutionary Transition ◽  
Evolutionary Transitions ◽  
Differentiated Cells ◽  
Labor Theory ◽  
Significant Events ◽  
Reproductive Life ◽  
History Of ◽  
Multicellular Organisms

AbstractThe transition from unicellular to multicellular organisms is one of the most significant events in the history of life. Key to this process is the emergence of Darwinian individuality at the higher level: groups must become single entities capable of reproduction for selection to shape their evolution. Evolutionary transitions in individuality are characterized by cooperation between the lower level entities and by division of labor. Theory suggests that division of labor may drive the transition to multicellularity by eliminating the trade-off between two incompatible processes that cannot be performed simultaneously in one cell. Here we examine the evolution of the most ancient multicellular transition known today, that of cyanobacteria, where we reconstruct the sequence of ecological and phenotypic trait evolution. Our results show that the prime driver of multicellularity in cyanobacteria was the expansion in metabolic capacity offered by nitrogen fixation, which was accompanied by the emergence of the filamentous morphology and succeeded by a reproductive life cycle. This was followed by the progression of multicellularity into higher complexity in the form of differentiated cells and patterned multicellularity.Significance StatementThe emergence of multicellularity is a major evolutionary transition. The oldest transition, that of cyanobacteria, happened more than 3 to 3.5 billion years ago. We find N2 fixation to be the prime driver of multicellularity in cyanobacteria. This innovation faced the challenge of incompatible metabolic processes since the N2 fixing enzyme (nitrogenase) is sensitive to oxygen, which is abundantly found in cyanobacteria cells performing photosynthesis. At the same time, N2-fixation conferred an adaptive benefit to the filamentous morphology as cells could divide their labour into performing either N2-fixation or photosynthesis. This was followed by the culmination of complex multicellularity in the form of differentiated cells and patterned multicellularity.

scholarly journals Morphological and genomic shifts in mole-rat 'queens' increase fecundity but reduce skeletal integrity

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Rachel A Johnston ◽  
Philippe Vullioud ◽  
Jack Thorley ◽  
Henry Kirveslahti ◽  
Leyao Shen ◽  
...  
Keyword(s):  
Division Of Labor ◽  
Morphological Plasticity ◽  
Skeletal Morphology ◽  
Eusocial Insects ◽  
Mole Rat ◽  
Gene Regulatory ◽  
Reproductive Division Of Labor ◽  
Reproductive Division ◽  
Skeletal Integrity ◽  
Vertebral Growth

In some mammals and many social insects, highly cooperative societies are characterized by reproductive division of labor, in which breeders and nonbreeders become behaviorally and morphologically distinct. While differences in behavior and growth between breeders and nonbreeders have been extensively described, little is known of their molecular underpinnings. Here, we investigate the consequences of breeding for skeletal morphology and gene regulation in highly cooperative Damaraland mole-rats. By experimentally assigning breeding 'queen' status versus nonbreeder status to age-matched littermates, we confirm that queens experience vertebral growth that likely confers advantages to fecundity. However, they also up-regulate bone resorption pathways and show reductions in femoral mass, which predicts increased vulnerability to fracture. Together, our results show that, as in eusocial insects, reproductive division of labor in mole-rats leads to gene regulatory rewiring and extensive morphological plasticity. However, in mole-rats, concentrated reproduction is also accompanied by costs to bone strength.

scholarly journals Topological constraints in early multicellularity favor reproductive division of labor

2019 ◽  
Author(s):  
David Yanni ◽  
Shane Jacobeen ◽  
Pedro Márquez-Zacarías ◽  
Joshua S Weitz ◽  
William C. Ratcliff ◽  
...  
Keyword(s):  
Division Of Labor ◽  
Resource Sharing ◽  
Evolutionary Biology ◽  
Large Body ◽  
Concave Function ◽  
Cellular Interactions ◽  
Wide Range ◽  
Classical Models ◽  
Reproductive Division Of Labor ◽  
Reproductive Division

Reproductive division of labor (e.g., germ-soma specialization) is a hallmark of the evolution of multicellularity, signifying the emergence of a new type of individual and facilitating the evolution of increased organismal complexity. A large body of work from evolutionary biology, economics, and ecology has shown that specialization is beneficial when further division of labor produces an accelerating increase in absolute productivity (i.e., productivity is a convex function of specialization). Here we show that reproductive specialization is qualitatively different from classical models of resource sharing, and can evolve even when the benefits of specialization are saturating (i.e., productivity is a concave function of specialization). Through analytical theory and evolutionary individual based simulations, our work demonstrates that reproductive specialization is strongly favored in sparse networks of cellular interactions, such as trees and filaments, that reflect the morphology of early, simple multicellular organisms, highlighting the importance of restricted social interactions in the evolution of reproductive specialization. More broadly, we find that specialization is strongly favored, despite saturating returns on investment, in a wide range of scenarios in which sharing is asymmetric.

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