scholarly journals Conflict over fertilization underlies the transient evolution of reinforcement

2020 ◽  
Author(s):  
Catherine A. Rushworth ◽  
Alison M. Wardlaw ◽  
Jeffrey Ross-Ibarra ◽  
Yaniv Brandvain
Keyword(s):  
Genetic Model ◽  
Male Gamete ◽  
Coordination Problem ◽  
Potential Conflict ◽  
Prezygotic Isolation ◽  
Male Gametes ◽  
Geographic Patterns ◽  
The Face ◽  
Postmating Prezygotic Isolation ◽  
Two Populations

ABSTRACTWhen two populations or species hybridize, their offspring often experience reductions in fitness relative to either parental population. The production of low fitness hybrids may be prevented by the evolution of increased prezygotic isolation; a process known as reinforcement. Theoretical challenges to the evolution of reinforcement are generally cast as a coordination problem — e.g., linkage disequilibrium between trait and preference loci is difficult to maintain in the face of recombination. However, the evolution of reinforcement also poses a potential conflict between mates. For example, the opportunity costs to hybridization may differ between the sexes or species. This is particularly likely for postmating prezygotic isolation, as the ability to fertilize both conspecific and heterospecific eggs is beneficial to male gametes, but heterospecific mating may incur a cost for female gametes. Motivated by this problem, we develop a population genetic model of interspecific conflict over reinforcement, inspired by ‘gametophytic factors’, which act as postmating prezygotic barriers among Zea mays subspecies. We demonstrate that this conflict results in the transient evolution of reinforcement – after female preference for a conspecific gamete trait rises to high frequency, male traits adaptively introgress into the other population. Ultimately the male gamete trait fixes in both species, and prezygotic isolation returns to pre-reinforcement levels. We interpret geographic patterns of isolation among Z. mays subspecies in light of these findings, and suggest when and how this conflict can be mediated. Our results suggest that sexual conflict may pose an understudied obstacle to the evolution of reinforcement via postmating prezygotic isolation.

The male gamete: spermatogenesis, maturation, function

2011 ◽  
pp. 1336-1347
Author(s):  
C. Marc Luetjens ◽  
Gerhard F. Weinbauer
Keyword(s):  
Male Gamete ◽  
Testicular Function ◽  
Sexual Hormones ◽  
Local Regulation ◽  
Experimental Animals ◽  
Male Gametes ◽  
Function Data ◽  
Maturation Function

The testes fulfil two essential functions: the production and maturation of the male gametes and synthesis and the secretion of the sexual hormones. Unless otherwise specified, this chapter describes the situation in the human and provides the basis for understanding the endocrine and local regulation of testicular function. Data obtained in experimental animals are presented when the corresponding human mechanisms are not known or cannot be clarified for ethical reasons.

scholarly journals Building a South African Human Rights Culture in the Face of Cultural Diversity: Context and Conflict

2012 ◽  
Vol 5 (1) ◽  
pp. 1-20 ◽  
Author(s):  
John Cantius Mubangizi
Keyword(s):  
South Africa ◽  
Human Rights ◽  
Cultural Diversity ◽  
Female Circumcision ◽  
Clear Understanding ◽  
Potential Conflict ◽  
Cultural Rights ◽  
The Face ◽  
Institutional Contexts ◽  
Virginity Testing

Abstract South Africa has faced enormous challenges since the advent of democracy in 1994. One of the difficulties in the post-apartheid era has been the building of a human rights culture in the context of substantial cultural diversity. In this paper, the constitutional, judicial and institutional contexts – which have consolidated and supported the expression of human rights in the face of cultural diversity – are reviewed. The focus on cultural rights in the constitution is discussed, and the relevance of several constitutional institutions in terms of ensuring human rights, is mentioned. With a clear understanding of the constitutional, judicial and institutional contexts in place, the paper discusses the potentially inherent conflict between human rights and cultural rights, using gender-related issues as a proxy. Several examples of this potential conflict are discussed, including female circumcision, virginity testing and polygamy. The importance of human rights education for informing the debate about cultural and human rights in South Africa is emphasized. The answers to the challenges associated with the clash between cultural rights and human rights are not simple, although pragmatically – in addition to the role of the available constitutional, judicial and institutional structures – they could reside in a cross-cultural debate.

scholarly journals Alternate-day feeding leads to improved glucose regulation on fasting days without significant weight loss in genetically obese mice

2019 ◽  
Vol 317 (3) ◽  
pp. R461-R469 ◽  
Author(s):  
Steven J. Swoap ◽  
Mark J. Bingaman ◽  
Elissa M. Hult ◽  
Noah J. Sandstrom
Keyword(s):  
Weight Loss ◽  
Insulin Sensitivity ◽  
Glucose Control ◽  
Genetic Model ◽  
Body Weight Loss ◽  
Littermate Control ◽  
The Face ◽  
Alternate Day Fasting ◽  
Ad Libitum ◽  
Ad Libitum Feeding

Alternate-day fasting (ADF) is effective for weight loss and increases insulin sensitivity in diet-induced obese rodents. However, the efficacy of ADF in genetic models of obesity has not been comprehensively studied. Mice that are deficient in leptin ( ob/ob mice) are obese, diabetic, and prone to deep bouts of torpor when fasted. We tested the hypotheses that an ADF protocol in ob/ob mice would result in 1) induction of torpor on fasted days, 2) minimal body weight loss if the mice experienced torpor, and 3) no improvement in glucose control in the absence of weight loss. Female ob/ob mice and littermate controls were assigned to 1) an ad libitum regimen or 2) an ADF regimen, consisting of fasting every other day with ad libitum feeding between fasts. Over a 19-day period, littermate control mice on the ADF regimen consumed the same amount of food as littermate control mice on the ad libitum regimen, whereas the ADF ob/ob mice consumed 37% less food than ad libitum ob/ob mice. Fasting days, but not fed days, led to torpor in both genotypes. Fasting days, but not fed days, led to weight loss in both genotypes relative to ad libitum controls. Fasting days, but not fed days, produced enhanced insulin sensitivity in both genotypes and normalized circulating glucose in ob/ob mice. These data demonstrate improved glucose control on fasting days with the use of ADF in a genetic model of obesity in the face of minimal weight loss.

High potassium seawater inhibits ascidian sperm chemotaxis, but does not affect the male gamete chemotaxis of a brown alga

Zygote ◽  
2019 ◽  
Vol 27 (4) ◽  
pp. 225-231 ◽  
Author(s):  
Nana Kinoshita-Terauchi ◽  
Kogiku Shiba ◽  
Makoto Terauchi ◽  
Francisco Romero ◽  
Héctor Vincente Ramírez-Gómez ◽  
...  
Keyword(s):  
Brown Algae ◽  
Brown Alga ◽  
Marine Invertebrates ◽  
Male Gamete ◽  
Female Gamete ◽  
General Strategy ◽  
High Potassium ◽  
Male Gametes ◽  
High K ◽  
Sperm Chemotaxis

SummaryMale gamete chemotaxis towards the female gamete is a general strategy to facilitate the sexual reproduction in many marine eukaryotes. Biochemical studies of chemoattractants for male gametes of brown algae have advanced in the 1970s and 1980s, but the molecular mechanism of male gamete responses to the attractants remains elusive. In sea urchin, a K+ channel called the tetraKCNG channel plays a fundamental role in sperm chemotaxis and inhibition of K+ efflux through this channel by high K+ seawater blocks almost all cell responses to the chemoattractant. This signalling mechanism could be conserved in marine invertebrates as tetraKCNG channels are conserved in the marine invertebrates that exhibit sperm chemotaxis. We confirmed that high K+ seawater also inhibited sperm chemotaxis in ascidian, Ciona intestinalis (robusta), in this study. Conversely, the male gamete chemotaxis towards the female gamete of a brown alga, Mutimo cylindricus, was preserved even in high K+ seawater. This result indicates that none of the K+ channels is essential for male gamete chemotaxis in the brown alga, suggesting that the signalling mechanism for chemotaxis in this brown alga is quite different from that of marine invertebrates. Correlated to this result, we revealed that the channels previously proposed as homologues of tetraKCNG in brown algae have a distinct domain composition from that of the tetraKCNG. Namely, one of them possesses two repeats of the six transmembrane segments (diKCNG) instead of four. The structural analysis suggests that diKCNG is a cyclic nucleotide-modulated and/or voltage-gated K+ channel.

Contradictions in Sustainability

1993 ◽  
Vol 20 (3) ◽  
pp. 217-222 ◽  
Author(s):  
Stephen R. Dovers ◽  
John W. Handmer
Keyword(s):  
Sustainable Development ◽  
Homo Sapiens ◽  
Change Resistance ◽  
Potential Conflict ◽  
Policy Debates ◽  
Nation States ◽  
Marginal Change ◽  
The Face ◽  
Intragenerational Equity ◽  
Innate Ability

Issues of environment and development are increasingly being analysed within the framework offered by sustainability and sustainable development. This article explores a number of deep-seated contradictions and tensions that exist within these concepts at least as they are currently construed. It is noted that these contradictions are often glossed over in intellectual and policy debates, but are nonetheless profound and should be made explicit.The contradictions identified and discussed in the paper are as follows:–the paradox of technology (cause or cure?);–uncertainty and decision-making (humility or arrogance in the face of ignorance?);–intergenerational and intragenerational equity (a politically impossible trade-off?);–economic growth versus ecological limits (is ‘sustainable development’ an oxymoron?);–the reconciliation of individual and collective interests, applying both to individuals in their society, and nation states in the international community;–the potential conflict between the diversity of democracy and purposeful action;–differing kinds of resilience in the face of change (resistance, marginal change, and adaptability); and–the question of whether or not optimization is anti-sustainability.In conclusion we ask what the implications of this labyrinth of contradictions are for moving towards a sustainable state. Are these contradictions too profound and thus insurmountable, or does Homo sapiens' apparently innate ability to live with contradiction and logical inconsistency offer a way out?

scholarly journals Assortative mating in hybrid zones is remarkably ineffective in promoting speciation

2019 ◽  
Author(s):  
Darren E. Irwin
Keyword(s):  
Assortative Mating ◽  
F1 Hybrids ◽  
Secondary Contact ◽  
Hybrid Zones ◽  
Mating Types ◽  
Postzygotic Isolation ◽  
Small Reduction ◽  
Hybrid Fitness ◽  
Prezygotic Isolation ◽  
Two Populations

AbstractAssortative mating and other forms of partial prezygotic isolation are often viewed as being more important than partial postzygotic isolation (low fitness of hybrids) early in the process of speciation. Here I simulate secondary contact between two populations (‘species’) to examine effects of pre- and postzygotic isolation in preventing blending. A small reduction in hybrid fitness (e.g., 10%) produces a narrower hybrid zone than a strong but imperfect mating preference (e.g., 10x stronger preference for conspecific over heterospecific mates). This is because, in the latter case, rare F1 hybrids find each other attractive (due to assortative mating), leading to the gradual buildup of a full continuum of intermediates between the two species. The cline is narrower than would result from purely neutral diffusion over the same number of generations, largely due to the frequency-dependent mating disadvantage of individuals of rare mating types. Hybrids tend to pay this cost of rarity more than pure individuals, meaning there is an induced postzygotic isolation effect of assortative mating. These results prompt a questioning of the concept of partial prezygotic isolation, since it is not very isolating unless there is also postzygotic isolation.

scholarly journals The relationship between robustness and evolution

2018 ◽  
Author(s):  
Pengyao Jiang ◽  
Martin Kreitman ◽  
John Reinitz
Keyword(s):  
Genetic Model ◽  
Initial Conditions ◽  
Genetic Locus ◽  
Genetic Mutation ◽  
Population Mean ◽  
Fitness Value ◽  
The Face ◽  
Evolutionary Trajectories ◽  
Mean Fitness ◽  
Developmental Noise

AbstractDevelopmental robustness (canalization) is a common attribute of traits in multi-cellular organisms. High robustness ensures the reproducibility of phenotypes in the face of environmental and developmental noise, but it also dampens the expression of genetic mutation, the fuel for adaptive evolution. A reduction in robustness may therefore be adaptive under certain evolutionary scenarios. To better understand how robustness influences phenotypic evolution, and to decipher conditions under which canalization itself evolves, a genetic model was constructed in which phenotype is explicitly represented as a collection of traits, calculated from genotype, and the degree of robustness can be explicitly controlled. The genes were sub jected to mutation, altering phenotype and fitness. We then simulated the dynamics of a population evolving under two classes of initial conditions, one in which the population is at a fitness optimum and one in which it is far away. The model is formulated with two robustness parameters in the genotype to phenotype map, controlling robustness over a tight (γ) or a broad (α) range of values. Within the robustness range determined by γ, high robustness results in a equilibrium population fitness closer to the optimal fitness value than low robustness. High robustness should be favored, therefore, under a constant optimal environment. This situation reverses when populations are challenged to evolve to a new phenotype optimum. In this situation, low robustness populations adapt faster than high robustness populations and reach higher equilibrium mean fitness. A larger set of phenotypes are accessable by mutation when robustness is low, in part explaining why low robustness is favored under this condition. A larger range of robustness could be sampled by varying α, revealing a complex relationship between robustness and both the initial rate of phenotypic adaptation as well as the final equilibrium population mean fitness. Intermediate values of α produced a bifurcation in evolutionary trajectories, with some populations remaining at low population mean fitness, and others escaping to achieve high population mean fitness. We then allowed robustness itself to be encoded by a mutable genetic locus that could co-evolve along with the phenotype under selection. Low robustness genotypes are initially favored when adapting to a new optimal phenotype. A high robustness genotype then replaces it, well before maximum fitness is achieved, and moreover appears to prevent further invasion into the population of a low-robustness genotype. This phenomenon was dependent on having tight linkage (and sufficiently low mutation rate) between the robustness locus and the loci encoding phenotype.

scholarly journals Plasmodium falciparum Calcium-Dependent Protein Kinase 4 is Critical for Male Gametogenesis and Transmission to the Mosquito Vector

mBio ◽  
2021 ◽  
Author(s):  
Sudhir Kumar ◽  
Meseret T. Haile ◽  
Michael R. Hoopmann ◽  
Linh T. Tran ◽  
Samantha A. Michaels ◽  
...  
Keyword(s):  
Male Gamete ◽  
Mosquito Vector ◽  
Parasite Life Cycle ◽  
Dependent Protein Kinase ◽  
Calcium Dependent ◽  
Male Gametogenesis ◽  
Phosphorylation Of Proteins ◽  
Male Gametes ◽  
Dependent Protein ◽  
Calcium Dependent Protein Kinase

Transmission of the malaria parasite to the mosquito vector is critical for the completion of the sexual stage of the parasite life cycle and is dependent on the release of male gametes from the gametocyte body inside the mosquito midgut. In the present study, we demonstrate that PfCDPK4 is critical for male gametogenesis and is involved in phosphorylation of proteins essential for male gamete emergence.

scholarly journals A comparative test of the gamete dynamics theory for the evolution of anisogamy in Bryopsidales green algae

2021 ◽  
Vol 8 (3) ◽  
Author(s):  
Tatsuya Togashi ◽  
Yusuke Horinouchi ◽  
Geoff A. Parker
Keyword(s):  
Life Cycle ◽  
Green Algae ◽  
Adult Stage ◽  
Male Gamete ◽  
Comparative Test ◽  
Disruptive Selection ◽  
Adult Size ◽  
Male Gametes ◽  
Selection For ◽  
Gamete Size

Gamete dynamics theory proposes that anisogamy arises by disruptive selection for gamete numbers versus gamete size and predicts that female/male gamete size (anisogamy ratio) increases with adult size and complexity. Evidence has been that in volvocine green algae, the anisogamy ratio correlates positively with haploid colony size. However, green algae show notable exceptions. We focus on Bryopsidales green algae. While some taxa have a diplontic life cycle in which a diploid adult (=fully grown) stage arises directly from the zygote, many taxa have a haplodiplontic life cycle in which haploid adults develop indirectly: the zygote first develops into a diploid adult (sporophyte) which later undergoes meiosis and releases zoospores, each growing into a haploid adult gametophyte. Our comparative analyses suggest that, as theory predicts: (i) male gametes are minimized, (ii) female gamete sizes vary, probably optimized by number versus survival as zygotes, and (iii) the anisogamy ratio correlates positively with diploid (but not haploid) stage complexity. However, there was no correlation between the anisogamy ratio and diploid adult stage size. Increased environmental severity (water depth) appears to drive increased diploid adult stage complexity and anisogamy ratio: gamete dynamics theory correctly predicts that anisogamy evolves with the (diploid) stage directly provisioned by the zygote.

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