Hanna Kokko

Hanna Kokko
Australian National University | ANU · Research School of Biology (RSB)

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202
Publications
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14,748
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Publications

Publications (202)
Article
Full-text available
Cooperation does not occur in a vacuum: interactions develop over time in social groups that undergo demographic changes. Intuition suggests that stable social environments favour developing few but strong reciprocal relationships (a 'focused' strategy), while volatile social environments favour the opposite: more but weaker social relationships (a...
Article
Meiotic drivers are selfish genetic elements that manipulate meiosis to increase their transmission to the next generation to the detriment of the rest of the genome. One example is the t haplotype in house mice, which is a naturally occurring meiotic driver with deleterious traits—poor fitness in polyandrous matings and homozygote inviability or i...
Preprint
Do environments or species traits that lower the mortality of individuals create selection for delaying senescence? Reading the literature creates an impression that mathematically oriented biologists cannot agree on the validity of George Williams' prediction (who claimed 'yes'). The abundance of models and opinions may bewilder those that are new...
Article
In species with obligate sexual reproduction, scarcity of males can occasionally limit female reproductive success. It is unclear, however, whether this impacts population-level persistence. Sexually deceptive orchids attract mate-searching male insects who lose time, mating opportunities and may even become sperm depleted by mating with flowers. T...
Preprint
Full-text available
Cooperative interactions do not occur in a vacuum, but develop over time in social groups that undergo demographic changes. Intuition suggests that stable social environments might favour individuals that develop few but strong reciprocal relationships (a 'focused' strategy), while volatile social environments do the opposite and favour individuals...
Article
Full-text available
In haplodiploids, (1) alleles spend twice as many generations in females as in males, (2) males are never heterozygous and therefore express recessive alleles, and (3) males sire daughters but not sons. Intralocus sexual conflict therefore operates differently in haplodiploids than in diploids and shares strong similarities with loci on X (or Z) ch...
Article
Full-text available
Recently, it was pointed out that classic models for the evolution of anisogamy do not take into account the possibility of parthenogenetic reproduction, even though sex is facultative in many relevant taxa (e.g., algae) that harbour both anisogamous and isogamous species. Here, we complement this recent analysis with an approach where we assume th...
Preprint
Full-text available
Recently, it was pointed out (Lehtonen et al., 2021) that classic models for the evolution of anisogamy do not take into account the possibility of parthenogenetic reproduction, even though sex is facultative in many relevant taxa (e.g. algae) that harbour both anisogamous and isogamous species. Here we complement the analysis of (Lehtonen et al.,...
Article
Full-text available
1. Sexes often differ more obviously in secondary sexual characteristics than in traits that appear naturally selected, despite conceivable benefits to intersexual niche partitioning. Genetic constraints may play a role in limiting sex‐specific niche evolution, however it is not clear why this limit should apply to naturally selected traits more th...
Preprint
Full-text available
Selection often favours large bodies, visible as Cope's rule over macroevolutionary time − but size increases are not inevitable. One understudied cost of large bodies is the high number of cell divisions and the associated risk of oncogenic mutations. Our elasticity analysis shows that selection against a proportional increase in size becomes ever...
Article
Cooperative interactions do not occur in a vacuum, but develop over time in social groups that undergo demographic changes. Intuition suggests that stable social environments might favour individuals that develop few but strong reciprocal relationships (a ‘focused’ strategy), while volatile social environments do the opposite and favour individuals...
Article
Selection often favours large bodies, visible as Cope’s rule over macroevolutionary time — but size increases are not inevitable. One understudied cost of large bodies is the high number of cell divisions and the associated risk of oncogenic mutations. Our elasticity analysis shows that selection against a proportional increase in size becomes ever...
Article
Full-text available
The predominance of sexual reproduction in eukaryotes remains paradoxical in evolutionary theory. Of the hypotheses proposed to resolve this paradox, the 'Red Queen hypothesis' emphasises the potential of antagonistic interactions to cause fluctuating selection, which favours the evolution and maintenance of sex. Whereas empirical and theoretical d...
Preprint
Full-text available
An increased appreciation of the ubiquity of cancer risk across the tree of life means we also need to understand the more robust cancer defences some species seem to have. Peto’s paradox, the finding that large-bodied species do not suffer from more cancer even if their lives require far more cell divisions than those of small species, can be expl...
Article
Full-text available
Multicellularity evolved independently in multiple lineages, yielding organisms with a wide range of adult sizes. Building an intact soma is not a trivial task, when dividing cells accumulate damage. Here, we study “ontogenetic management strategies,” that is rules of dividing, differentiating and killing somatic cells, to examine two questions: fi...
Article
Why is life paced so differently across as well as within organisms? Can one expect across-species patterns to be repeated within a species too, among individuals? The answer to these questions requires understanding conditions under which reaction norms evolve. We provide an overview of what we believe to be understudied areas of life-history theo...
Preprint
Full-text available
The predominance of sexual reproduction in eukaryotes remains paradoxical in evolutionary theory. Of the hypotheses proposed to resolve this paradox, the “Red Queen hypothesis” emphasizes the potential of antagonistic interactions to cause fluctuating selection, which favours the evolution and maintenance of sex. While empirical and theoretical dev...
Article
Full-text available
For organisms living in unpredictable environments, timing important life‐history events is challenging. One way to deal with uncertainty is to spread the emergence of offspring across multiple years via dormancy. However, timing of emergence is not only important among years, but also within each growing season. Here, we study the evolutionary int...
Preprint
The maintenance of cooperation is difficult whenever collective action problems are vulnerable to freeriding (reaping the benefits without contributing to the maintenance of the good). We identify a novel factor that can make a system tolerate an extent of freeriding. If a population consists of discrete types with demographically distinct roles, s...
Article
An increased appreciation of the ubiquity of cancer risk across the tree of life means we also need to understand the more robust cancer defences some species seem to have. Peto’s paradox, the finding that large-bodied species do not suffer from more cancer even if their lives require far more cell divisions than those of small species, can be expl...
Article
Full-text available
JBS Haldane is widely quoted to have quipped that the Creator, if one exists, has an inordinate fondness for beetles. Although Coleoptera may not be the most speciose order once Hymenopteran diversity is fully accounted for, as a whole the very clear differences in species diversity among taxa require an explanation. Here we use stochastic simulati...
Preprint
Full-text available
Sexual interactions play an important role in the evolution of reproductive isolation, with important consequences for speciation. Theoretical studies have focused on the evolution of mate preferences in each sex separately. However, mounting empirical evidence suggests that premating isolation often involves mutual mate choice. Here, using a popul...
Article
Biological diversity abounds in potential study topics. Studies of model systems have their advantages, but reliance on a few well-understood cases may create false impressions of what biological phenomena are the norm. Here I focus on facultative sex, which is often hailed as offering the best of both worlds, in that rare sex offers benefits almos...
Article
Full-text available
Providing parental care often reduces additional mating opportunities. Paternal care becomes easier to understand if trade-offs between mating and caring remain mild. The black coucal Centropus grillii combines male-only parental care with 50% of all broods containing young sired by another male. To understand how much caring for offspring reduces...
Article
Full-text available
Resource competition is a major driver of dispersal: an emigrating individual leaves more resources to its kin. Existing models of sex-biased dispersal rarely consider intersexual competition for resources. Instead, male reproductive success is often solely assumed to depend on female availability, implying a tacit assumption that male presence nev...
Preprint
Full-text available
Resource competition is a major driver of dispersal: an emigrating individual leaves more resources to its kin. Existing models of sex-biased dispersal rarely consider intersexual competition for resources. Instead, male reproductive success is often solely assumed to depend on female availability, implying a tacit assumption that male presence nev...
Article
Natural populations often experience environments that vary across space and over time, leading to spatio-temporal variation of the fitness of a genotype. If local conditions are poor, organisms can disperse in space (physical movement) or time (dormancy, diapause). Facultatively sexual organisms can switch between asexual and sexual reproduction,...
Article
Full-text available
It is unclear why sexually reproducing isogamous species frequently contain just two self-incompatible mating types. Deterministic theory suggests that since rare novel mating types experience a selective advantage (by virtue of their many potential partners), the number of mating types should consistently grow. However, in nature, species with tho...
Article
Adaptive explanations for dormancy often invoke bet hedging, where reduced mean fitness can be adaptive if it associates with reduced fitness variance. Sex allocation theory typically ignores variance effects and focuses on mean fitness. For many cyclical parthenogens, these themes become linked, as only sexually produced eggs undergo the dormancy...
Article
Full-text available
Local adaptation to rare habitats is difficult due to gene flow, but can occur if the habitat has higher productivity. Differences in offspring phenotypes have attracted little attention in this context. We model a scenario where the rarer habitat improves offspring's later competitive ability – a carryover effect that operates on top of local adap...
Article
Full-text available
Warning signals are an effective defence strategy for aposematic prey, but only if they are recognized by potential predators. If predators must eat prey to associate novel warning signals with unpalatability, how can aposematic prey ever evolve? Using experiments with great tits (Parus major) as predators, we show that social transmission enhances...
Article
Cyclical parthenogenesis presents an interesting challenge for the study of sex allocation, as individuals’ allocation decisions involve both the choice between sexual and asexual reproduction, and the choice between sons and daughters. Male production is therefore expected to depend on ecological and evolutionary drivers of overall investment in s...
Data
Appendix S1. Methods. Table S1. Examples of heritability (h 2) estimates in the reviewed studies. Table S2. Models of dispersal evolution and assumptions made on the genetic architecture of the evolving traits.
Article
The timing of sex in facultatively sexual organisms is critical to fitness, due to the differing demographic consequences of sexual versus asexual reproduction. In addition to the costs of sex itself, an association of sex with the production of dormant life stages also influences the optimal use of sex, especially in environments where resting egg...
Article
Full-text available
Dispersal is ubiquitous throughout the tree of life: factors selecting for dispersal include kin competition, inbreeding avoidance and spatiotemporal variation in resources or habitat suitability. These factors differ in whether they promote male and female dispersal equally strongly, and often selection on dispersal on one sex depends on how much...
Article
Does the progress in understanding evolutionary theory depend on the species that is doing the investigation? This question is difficult to answer scientifically, as we are dealing with an n = 1 scenario: every individual who has ever written about evolution is a human being. I will discuss, first, whether we get the correct answer to questions if...
Article
Full-text available
Dispersal is a process of central importance for the ecological and evolutionary dynamics of populations and communities, because of its diverse consequences for gene flow and demography. It is subject to evolutionary change, which begs the question, what is the genetic basis of this potentially complex trait? To address this question, we (i) revie...
Article
The rate at which a population grows and spreads can depend on individual behaviour and interactions with others. In many species with two sexes, males and females differ in key life history traits (e.g. growth, survival, dispersal), which can scale up to affect population rates of growth and spread. In sexually reproducing species, the mechanics o...
Article
Isogamy is a reproductive system where all gametes are morphologically similar, especially in terms of size. Its importance goes beyond specific cases: to this day non-anisogamous systems are common outside of multicellular animals and plants, they can be found in all eukaryotic super-groups, and anisogamous organisms appear to have isogamous ances...
Article
Full-text available
The idea for this project started over lunch in an Italian restaurant in Copenhagen in 2010. We were not planning to talk about sex at that time, but to discuss the evolution of uniparental inheritance. But as they say, one thing leads to another, and we started to talk about sex and its underappreciated weirdness. And the need for a project like t...
Article
For migratory species, the timing of arrival at breeding grounds is an important determinant of fitness. Too early arrival at the breeding ground is associated with various costs, and we focus on one understudied cost: that migrants can experience a higher risk of predation if arriving earlier than the bulk of the breeding population. We show, usin...
Article
Meiotic drivers are genetic variants that selfishly manipulate the production of gametes to increase their own rate of transmission, often to the detriment of the rest of the genome and the individual that carries them. This genomic conflict potentially occurs whenever a diploid organism produces a haploid stage, and can have profound evolutionary...
Article
Full-text available
In evolutionary biology, bet-hedging refers to a strategy that reduces the variance of reproductive success at the cost of reduced mean reproductive success. In unpredictably fluctuating environments, bet-hedgers benefit from higher geometric mean fitness despite having lower arithmetic mean fitness than their specialist competitors. We examine the...
Article
Evolutionary models of dispersal frequently lack explicit reference to the age or sex of the individuals that disperse. This contrasts with reality where dispersal behavior strongly depends on individuals’ state, including age. To study why natal dispersal occurs more commonly than breeding dispersal, we investigate the interplay of 2 categories of...
Article
Full-text available
The parents’ phenotype, or the environment they create for their young, can have longlasting effects on their offspring, with profound evolutionary consequences. Yet, virtually no work has considered how such parental effects might change the adaptive value of behavioural traits expressed by offspring upon reaching adulthood. To address this proble...
Article
Full-text available
Simultaneous hermaphroditism is predicted to be unstable at high mating rates given an associated increase in sperm competition. The existence of reciprocal egg trading, which requires both hermaphroditism and high mating rates to evolve, is consequently hard to explain. We show using mathematical models that the presence of a trading economy creat...
Article
Full-text available
Polymorphic warning signals in aposematic species are enigmatic because predator learning and discrimination should select for the most common coloration, resulting in positive frequency-dependent survival selection. Here, we investigated whether differential mating success could create sufficiently strong negative frequency-dependent selection fo...
Article
Successful invasions by sexually reproducing species depend on the ability of individuals to mate. Finding mates can be particularly challenging at low densities (a mate-finding Allee effect), a factor that is only implicitly accounted for by most invasion models, which typically assume asexual populations. Existing theory on single-sex populations...
Article
Social monogamy predominates in avian breeding systems, but most socially monogamous species engage in promiscuous extra-pair copulations (EPCs). The reasons behind this remain debated, and recent empirical work has uncovered patterns that do not seem to fit existing hypotheses. In particular, some results seem to contradict the inbreeding avoidanc...
Article
Segregation distorters located on sex chromosomes are predicted to sweep to fixation and cause extinction via a shortage of one sex, but in nature they are often found at low, stable frequencies. One potential resolution to this long-standing puzzle involves female multiple mating (polyandry). Because many meiotic drivers severely reduce the sperm...
Article
Segregation distorters located on sex chromosomes are predicted to sweep to fixation and cause extinction via a shortage of one sex, but in nature they are often found at low, stable frequencies. One potential resolution to this long-standing puzzle involves female multiple mating (polyandry). Because many meiotic drivers severely reduce the sperm...
Article
Generally, sex-specific mortality is not expected to affect optimal patterns of sex allocation. Several authors have, however, made verbal arguments that this is not true if juvenile mortality is sex-specific during the period of parental care. Here, we provide formal mathematical models exploring the effect of such mortality on optimal sex allocat...
Article
Full-text available
Egg trading—the alternating exchange of egg parcels during mating by simul- taneous hermaphrodites—is one of the best-documented examples of reciprocity between non-relatives. By offering eggs only to partners who reciprocate, traders increase their repro- ductive success in the male role, but at a potential cost of delaying or reducing fertilisati...
Article
Full-text available
Insect communities consist of aposematic species with efficient warning colours against predation, as well as abundant examples of crypsis. To understand such coexistence, we here report results from a field experiment where relative survival of artificial larvae, varying in conspicuousness, was estimated in natural bird communities over an entire...
Article
Full-text available
When female fecundity is relatively independent of male abundance, while male reproduction is proportional to female abundance, females have a larger effect on population dynamics than males (i.e. female demographic dominance). This population dynamic phenomenon might not appear to influence evolution, because male and female genomes still contribu...
Chapter
The evolution of mate choice remains controversial, particularly when the choosy sex receives nothing but genes from their mates. Indirect benefits are predicted to be meagre because persistent female choice depletes genetic variation in the male traits under sexual selection. This chapter suggests that the theoretical basis of local adaptation and...
Conference Paper
Background/Question/Methods A key characteristic of whether a newly introduced species will be invasive is the rate at which it is able to spread in a new environment. Spread rate (or invasion speed) depends in large part on dispersal ability, which may differ among individuals (e.g. according to sex). For sexually reproducing organisms, another...
Article
Full-text available
Within and across taxa, there is much variation in the mode of fertilization, that is, whether eggs and/or sperm are released or kept inside or on the surface of the parent's body. Although the evolutionary consequences of fertilization mode are far-reaching, transitions in the fertilization mode itself have largely escaped theoretical attention. H...
Article
Evolutionary conflicts of interest arise whenever genetically different individuals interact and their routes to fitness maximization differ. Sexual selection favors traits that increase an individual's competitiveness to acquire mates and fertilizations. Sexual conflict occurs if an individual of sex A's relative fitness would increase if it had a...
Article
Full-text available
Jussi Lehtonen and Hanna Kokko provide a quick guide on definitions of sex.
Article
Although dispersal requires context-dependent decision-making in three distinct stages (emigration, transit, immigration), these decisions are commonly ignored in simple models of dispersal. For sexually reproducing organisms, mate availability is an important factor in dispersal decisions. Difficulty finding mates can lead to an Allee effect where...
Article
Achieving sufficient connectivity between populations is essential for persistence, but costs of dispersal may select against individual traits or behaviours that, if present, would improve connectivity. Existing dispersal models tend to ignore the multitude of risks to individuals: while many assess the effect of mortality costs, there is also a r...
Article
Full-text available
An increasing number of publishers and funding agencies require public data archiving (PDA) in open-access databases. PDA has obvious group benefits for the scientific community, but many researchers are reluctant to share their data publicly because of real or perceived individual costs. Improving participation in PDA will require lowering costs a...
Conference Paper
Background/Question/Methods Polyandry, by elevating sexual conflict and selecting for reduced male care relative to monandry, may exacerbate the cost of sex and thereby seriously impact population fitness. On the other hand, polyandry has a number of possible population-level benefits over monandry, such as increased sexual selection leading to f...
Article
Sperm competition and uncertainty of paternity hamper the evolution of male parental care. Thus, maternal care predominates in most taxa. What if males can, however, limit cuckoldry by guarding the eggs postmating? Here, we show that this provides a reason to reconsider an old and nowadays rather discredited hypothesis: that external fertilization...
Article
Full-text available
Sex allocation theory explains why most species produce equal numbers of sons and daughters, and highlights situations that select for deviation from this norm. Past research has, however, heavily focused on situations with discrete generations. When temporally varying generational overlap affects future mate availability, models predict cyclical s...
Article
It is well recognized that sex allocation strategies can be influenced by sexual selection, when females adjust offspring sex ratios in response to their mates' attractiveness. Yet the reciprocal influence of strategic sex allocation on processes of sexual selection has only recently been revealed. Recent theoretical work demonstrates that sex allo...
Article
Sexual parasites offer unique insights into asexual and sexual reproduction. They mate with a 'host' whose genetic contribution is discarded either immediately (in androgenesis or gynogenesis) or after a delay of one generation (in hybridogenesis). The discarded genome can be maternal or paternal, implying that not only females but also males can r...
Data
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##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##
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##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##
Article
Our biosphere is abundant with unique and small genes for which no homologues are known. These genes, often referred to as orphans or ORFans, are commonly found in bacteriophage genomes but their origins remain unclear. We discovered five novel tectivirus-like genetic elements by screening more than five-hundred Bacillus strains. A highly variable...
Article
Guidelines for submitting commentsPolicy: Comments that contribute to the discussion of the article will be posted within approximately three business days. We do not accept anonymous comments. Please include your email address; the address will not be displayed in the posted comment. Cell Press Editors will screen the comments to ensure that they...
Article
The action of sexual selection is highly variable among taxa. This creates challenges when trying to generalize (e.g. determine if a particular relationship exists based on its average strength, or if it varies in response to theoretically relevant factors). Con-sequently, accounting for moderating factors is likely to be crucial to explain differe...