Organelle bottlenecks facilitate evolvability by traversing heteroplasmic fitness valleys.

Bioenergetic organelles-mitochondria and plastids-retain their own genomes (mtDNA and ptDNA), and these organelle DNA (oDNA) molecules are vital for eukaryotic life. Like all genomes, oDNA must be able to evolve to suit new environmental challenges. However, mixed oDNA populations in cells can challenge cellular bioenergetics, providing a penalty to the appearance and adaptation of new mutations.

Selection for biparental inheritance of mitochondria under hybridization and mitonuclear fitness interactions.

Uniparental inheritance (UPI) of mitochondria predominates over biparental inheritance (BPI) in most eukaryotes. However, examples of BPI of mitochondria, or paternal leakage, are becoming increasingly prevalent. Most reported cases of BPI occur in hybrids of distantly related sub-populations.

Adherence to public institutions that foster cooperation.

Humans typically consider altruism a moral good and condition their social behavior on the moral reputations of others. Indirect reciprocity explains how social norms and reputations support cooperation: individuals cooperate with others who are considered good. Indirect reciprocity works when an institution monitors and publicly broadcasts moral reputations.

Avoiding organelle mutational meltdown across eukaryotes with or without a germline bottleneck.

Mitochondrial DNA (mtDNA) and plastid DNA (ptDNA) encode vital bioenergetic apparatus, and mutations in these organelle DNA (oDNA) molecules can be devastating. In the germline of several animals, a genetic "bottleneck" increases cell-to-cell variance in mtDNA heteroplasmy, allowing purifying selection to act to maintain low proportions of mutant mtDNA. However, most eukaryotes do not sequester a germline early in development, and even the animal bottleneck remains poorly understood.

Beyond the "selfish mitochondrion" theory of uniparental inheritance: A unified theory based on mutational variance redistribution.

"Selfish" gene theories have offered invaluable insight into eukaryotic genome evolution, but they can also be misleading. The "selfish mitochondrion" hypothesis, developed in the 90s explained uniparental organelle inheritance as a mechanism of conflict resolution, improving cooperation between genetically distinct compartments of the cell. But modern population genetic models provided a more general explanation for uniparental inheritance based on mutational variance redistribution, modulating the efficiency of both purifying and adaptive selection.

Sexually antagonistic evolution of mitochondrial and nuclear linkage.

Across eukaryotes, genes encoding bioenergetic machinery are located in both mitochondrial and nuclear DNA, and incompatibilities between the two genomes can be devastating. Mitochondria are often inherited maternally, and theory predicts sex-specific fitness effects of mitochondrial mutational diversity. Yet how evolution acts on linkage patterns between mitochondrial and nuclear genomes is poorly understood.

Evolution of empathetic moral evaluation.

Social norms can promote cooperation by assigning reputations to individuals based on their past actions. A good reputation indicates that an individual is likely to reciprocate. A large body of research has established norms of moral assessment that promote cooperation, assuming reputations are objective.

The evolution of individuality revisited.

Evolutionary theory is formulated in terms of individuals that carry heritable information and are subject to selective pressures. However, individuality itself is a trait that had to evolve - an individual is not an indivisible entity, but a result of evolutionary processes that necessarily begin at the lower level of hierarchical organisation. Traditional approaches to biological individuality focus on cooperation and relatedness within a group, division of labour, policing mechanisms and strong selection at the higher level.

Sexual conflict explains the extraordinary diversity of mechanisms regulating mitochondrial inheritance.

Background: Mitochondria are predominantly inherited from the maternal gamete, even in unicellular organisms. Yet an extraordinary array of mechanisms enforce uniparental inheritance, which implies shifting selection pressures and multiple origins.

Results: We consider how this high turnover in mechanisms controlling uniparental inheritance arises using a novel evolutionary model in which control of mitochondrial transmission occurs either during spermatogenesis (by paternal nuclear genes) or at/after fertilization (by maternal nuclear genes).

Mitigating Mitochondrial Genome Erosion Without Recombination.

Mitochondria are ATP-producing organelles of bacterial ancestry that played a key role in the origin and early evolution of complex eukaryotic cells. Most modern eukaryotes transmit mitochondrial genes uniparentally, often without recombination among genetically divergent organelles. While this asymmetric inheritance maintains the efficacy of purifying selection at the level of the cell, the absence of recombination could also make the genome susceptible to Muller's ratchet.

Selection for Mitochondrial Quality Drives Evolution of the Germline.

The origin of the germline-soma distinction is a fundamental unsolved question. Plants and basal metazoans do not have a germline but generate gametes from pluripotent stem cells in somatic tissues (somatic gametogenesis). In contrast, most bilaterians sequester a dedicated germline early in development.

Evolutionary dynamics of cytoplasmic segregation and fusion: Mitochondrial mixing facilitated the evolution of sex at the origin of eukaryotes.

Sexual reproduction is a trait shared by all complex life, but the complete account of its origin is missing. Virtually all theoretical work on the evolution of sex has been centered around the benefits of reciprocal recombination among nuclear genes, paying little attention to the evolutionary dynamics of multi-copy mitochondrial genomes. Here I develop a mathematical model to study the evolution of nuclear alleles inducing cell fusion in an ancestral population of clonal proto-eukaryotes.

Conflict and cooperation in eukaryogenesis: implications for the timing of endosymbiosis and the evolution of sex.

Roughly 1.5-2.0 Gya, the eukaryotic cell evolved from an endosymbiosis of an archaeal host and proteobacterial symbionts.

Geometrical defects in two-dimensional melting of many-particle Yukawa systems.

We present a theoretical polygon construction analysis of two-dimensional melting and freezing transitions in many-particle Yukawa systems. Two-dimensional melting transitions can be characterized as proliferation of geometrical defects--nontriangular polygons, obtained by removing unusually long bonds in the triangulation of particle positions. A liquid state is characterized by the temperature-independent number of quadrilaterals and linearly increasing number of pentagons.