Patterns and processes of sex chromosome evolution
Lead Research Organisation:
University of Sheffield
Department Name: School of Biosciences
Abstract
From the spectacular tail of the male peacock to the dazzling courtship dance of male spiders, males and females across the animal kingdom often look and behave very differently. However, the two sexes share an almost identical set of genes, so how do these remarkable sex differences arise? The answer is thought to lie with the sex chromosomes, as they are the only region of the genome to differ between females and males. In humans, where males posses one X and one Y chromosome but females have two X chromosomes, the Y chromosome is the essence of masculinity. However, other animals can have different types of sex chromosomes. For instance, birds have Z and W sex chromosomes. Males have two Z chromosomes and females have one Z and one W chromosome. Furthermore, whereas all mammals are XY and all birds are ZW, geckos are one of the few animal groups that possess both XY and ZW sex chromosomes in different species. My research aims to characterise this diversity of sex chromosomes in birds and geckos and explore their role in generating biological differences between males and females.
Just as the Y chromosome is important for maleness in mammals, the W chromosome is particularly interesting for understanding female traits, such as egg laying in birds. However, the survival of both of these gender-limited chromosomes is under threat. The way for chromosomes to eliminate faulty mutations is by pairing up and swapping genes during reproduction. The single W and Y chromosomes do not have this option because they have no partner to pair with, and so cannot repair genetic mistakes. Over time, these chromosomes have decayed, losing 90% of their original gene content, and are now largely genetic wastelands. But is this degeneration of the Y and W chromosomes terminal? Does this mean the Y chromosome in humans and ultimately males will become extinct?
The key to answering this question lies in the genes that have survived: have they been preserved because their function is so critical or is their survival the result of random chance? My research will explore exactly how genes resist these strong degradative forces by studying bird sex chromosomes, which offer unparalleled insight into the process of degeneration. This is because all birds originally shared an identical W chromosome, but over millions of years the once-identical W chromosome has decayed independently in different bird species. This evolutionary repetition makes it possible to test whether the same sets of genes have survived on the W chromosome across birds and to identify their role in female traits.
However, in order to understand how sex differences are encoded in the genome it is not enough to study only the gender-limited Y and W chromosomes. Studies of the Z and X chromosomes can also help explain how striking differences between males and females evolve. In birds and some gecko species, males have two copies of the Z chromosome whereas females possess only one. Therefore, the Z is thought to encode flashy plumage and elaborate courtship songs in males. Similarly, as the X chromosome is present more often in females than males, it is thought to play a major role in determining female functions. As geckos possess both XY and ZW sex chromosomes they provide an excellent opportunity to explore the roles played by both the X and Z chromosomes in determining sexual differences. I will therefore study this natural variation across geckos and ask how the roles played by the X and Z chromosomes differ from each other.
Together, my research will shed much needed light on the huge diversity by which sex is determined across the animal kingdom. More importantly, by studying the role played by different types of sex chromosomes in multiple animals, my research has the power to greatly advance our understanding of the evolutionary mechanisms responsible for producing the dazzling array of sexual variety exhibited in the animal kingdom.
Just as the Y chromosome is important for maleness in mammals, the W chromosome is particularly interesting for understanding female traits, such as egg laying in birds. However, the survival of both of these gender-limited chromosomes is under threat. The way for chromosomes to eliminate faulty mutations is by pairing up and swapping genes during reproduction. The single W and Y chromosomes do not have this option because they have no partner to pair with, and so cannot repair genetic mistakes. Over time, these chromosomes have decayed, losing 90% of their original gene content, and are now largely genetic wastelands. But is this degeneration of the Y and W chromosomes terminal? Does this mean the Y chromosome in humans and ultimately males will become extinct?
The key to answering this question lies in the genes that have survived: have they been preserved because their function is so critical or is their survival the result of random chance? My research will explore exactly how genes resist these strong degradative forces by studying bird sex chromosomes, which offer unparalleled insight into the process of degeneration. This is because all birds originally shared an identical W chromosome, but over millions of years the once-identical W chromosome has decayed independently in different bird species. This evolutionary repetition makes it possible to test whether the same sets of genes have survived on the W chromosome across birds and to identify their role in female traits.
However, in order to understand how sex differences are encoded in the genome it is not enough to study only the gender-limited Y and W chromosomes. Studies of the Z and X chromosomes can also help explain how striking differences between males and females evolve. In birds and some gecko species, males have two copies of the Z chromosome whereas females possess only one. Therefore, the Z is thought to encode flashy plumage and elaborate courtship songs in males. Similarly, as the X chromosome is present more often in females than males, it is thought to play a major role in determining female functions. As geckos possess both XY and ZW sex chromosomes they provide an excellent opportunity to explore the roles played by both the X and Z chromosomes in determining sexual differences. I will therefore study this natural variation across geckos and ask how the roles played by the X and Z chromosomes differ from each other.
Together, my research will shed much needed light on the huge diversity by which sex is determined across the animal kingdom. More importantly, by studying the role played by different types of sex chromosomes in multiple animals, my research has the power to greatly advance our understanding of the evolutionary mechanisms responsible for producing the dazzling array of sexual variety exhibited in the animal kingdom.
Planned Impact
1. Who will benefit from this research?
Poultry industry
Zoos, aviaries and wildlife parks
Pet owners
General public
Women in Science
2. How will they benefit from this research?
1. Poultry Industry
Egg laying rate, or female fecundity, is a critical component of the poultry industry. The W chromosome is known to be key in female fecundity and this project will generate a catalogue of W-linked genes in three agriculturally important species; turkey, duck and guineafowl. In particular, the turkey is central to the North American poultry industry and production is worth $5.3 billion (USA Department of Agriculture, National Agricultural Statistics Service 2014 values). The dataset of W-linked genes generated during this fellowship will present a useful list of selection targets to breeders to increase productivity.
2. Zoo, aviaries and wildlife parks
Sexual dimorphism is arguably one of the most conspicuous sources of biodiversity in the animal kingdom. The proposed work will shed light on sexual dimorphism at the genomic level and the evolutionary processes associated with sex. Displays and events based on this research would therefore greatly assist wildlife parks in raising awareness of the natural world and igniting the public's interest in evolution. Furthermore, as geckos and zebra finches are common features of aviaries and reptile houses, the educational potential of these establishments would benefit from displays outlining the current scientific research in these species.
3. Pet owners
Lizards and birds are popular domestic pets in the UK and there are a large number of active societies established by enthusiasts and breeders. Knowledge on the mechanisms by which sex is determined in these species, as well as the evolutionary processes shaping biological differences between males and females, will be of particular interest to society members.
4. General public
Sex is a topic of widespread interest and can generate sizeable attention from the general public. Therefore, the charismatic species in this project (lizards, birds), together with the dynamic research topic (evolution, sex) and innovative methods (whole genome sequencing), will spark the general public's interest in evolution and genetics. In doing so, this will inspire young scientists and encourage them to pursue careers in science. I can also act as a female role model to young scientists and promote women in science.
I am ideally positioned to disseminate my research findings effectively to the beneficiaries I have identified. I have already participated in public outreach events and attended a workshop designed to equip attendees with a diverse toolkit of communication skills. Using my skillset and building on my previous experience, I have outlined a range of approaches to transfer knowledge and information to the relevant parties in my Pathways to Impact.
Poultry industry
Zoos, aviaries and wildlife parks
Pet owners
General public
Women in Science
2. How will they benefit from this research?
1. Poultry Industry
Egg laying rate, or female fecundity, is a critical component of the poultry industry. The W chromosome is known to be key in female fecundity and this project will generate a catalogue of W-linked genes in three agriculturally important species; turkey, duck and guineafowl. In particular, the turkey is central to the North American poultry industry and production is worth $5.3 billion (USA Department of Agriculture, National Agricultural Statistics Service 2014 values). The dataset of W-linked genes generated during this fellowship will present a useful list of selection targets to breeders to increase productivity.
2. Zoo, aviaries and wildlife parks
Sexual dimorphism is arguably one of the most conspicuous sources of biodiversity in the animal kingdom. The proposed work will shed light on sexual dimorphism at the genomic level and the evolutionary processes associated with sex. Displays and events based on this research would therefore greatly assist wildlife parks in raising awareness of the natural world and igniting the public's interest in evolution. Furthermore, as geckos and zebra finches are common features of aviaries and reptile houses, the educational potential of these establishments would benefit from displays outlining the current scientific research in these species.
3. Pet owners
Lizards and birds are popular domestic pets in the UK and there are a large number of active societies established by enthusiasts and breeders. Knowledge on the mechanisms by which sex is determined in these species, as well as the evolutionary processes shaping biological differences between males and females, will be of particular interest to society members.
4. General public
Sex is a topic of widespread interest and can generate sizeable attention from the general public. Therefore, the charismatic species in this project (lizards, birds), together with the dynamic research topic (evolution, sex) and innovative methods (whole genome sequencing), will spark the general public's interest in evolution and genetics. In doing so, this will inspire young scientists and encourage them to pursue careers in science. I can also act as a female role model to young scientists and promote women in science.
I am ideally positioned to disseminate my research findings effectively to the beneficiaries I have identified. I have already participated in public outreach events and attended a workshop designed to equip attendees with a diverse toolkit of communication skills. Using my skillset and building on my previous experience, I have outlined a range of approaches to transfer knowledge and information to the relevant parties in my Pathways to Impact.
People |
ORCID iD |
Alison Wright (Principal Investigator / Fellow) |
Publications
Cooney C
(2020)
Ecology and allometry predict the evolution of avian developmental durations
in Nature Communications
Cooney CR
(2021)
Constraint and divergence in the evolution of male and female recombination rates in fishes.
in Evolution; international journal of organic evolution
Darolti I
(2020)
Guppy Y Chromosome Integrity Maintained by Incomplete Recombination Suppression.
in Genome biology and evolution
Darolti I
(2019)
Extreme heterogeneity in sex chromosome differentiation and dosage compensation in livebearers
in Proceedings of the National Academy of Sciences
Fox EA
(2019)
ngsLD: evaluating linkage disequilibrium using genotype likelihoods.
in Bioinformatics (Oxford, England)
Furman BLS
(2020)
Sex Chromosome Evolution: So Many Exceptions to the Rules.
in Genome biology and evolution
Lin Y
(2022)
Gene duplication to the Y chromosome in Trinidadian Guppies.
in Molecular ecology
Mank JE
(2020)
Signature of sexual conflict is actually conflict resolved.
in Molecular ecology
Palmer DH
(2019)
How to identify sex chromosomes and their turnover.
in Molecular ecology
Price P
(2021)
Detecting Signatures Of Selection In Regulatory Variation
Description | I found that the majority of sexual conflict is produced through conflicting selection over reproductive interests of males and females, and that sexual conflict has the potential to maintain genetic diversity through balancing selection. I also showed that regulatory evolution, the evolution of gene expression differences between males and females, is a rapid and efficient route to resolving sexual conflict. Sex-biased expression decouples male and female phenotypes, leading to the evolution of separate sex-specific architectures where alleles have phenotypic effects in one sex but not the other. I also showed that alternative splicing, a common yet understudied regulatory mechanism, is key to sexual dimorphisms. While sex chromosomes clearly are important for sexual dimorphism, the sex differences in gene expression may be a quicker and more effective route to sex-specific adaptation. |
Exploitation Route | Disease incidence and response to medication is strongly influenced by sex. My work highlights the large transcriptional differences exhibited between males and females and therefore has biomedical consequences. |
Sectors | Environment,Healthcare,Other |
URL | https://evolutionletters.wordpress.com/2018/02/10/battle-of-the-sexes-resolved/ |
Description | By studying the evolution of the sex chromosomes in a group of birds with agricultural importance, my work has the potential to shed light on the genetic basis of fertility. This is of key important to industry and agriculture. As I obtain further results, I plan to communicate my findings to these groups. Furthermore, my work sheds light on the genetic basis of diversity in chicken breeds, which is of significant interest to poultry breeders. I have been in contact with multiple societies including Rare Poultry Society, The Poultry Club of Great Britain and British Waterfowl Association, who are very interested in my findings. We plan to communicate my research to poultry breeders through articles in society newsletters. I am committed to communicating my research to a wide range of beneficiaries and the general public. I promote women in science and have registered to participate in Soapbox Science, a public outreach event for women scientists and their research. I also support the 500 Women Scientists and their 'Request a Woman Scientist' programme. |
First Year Of Impact | 2017 |
Sector | Agriculture, Food and Drink,Education |
Impact Types | Societal |
Description | Great Lakes Fishery Commission |
Amount | $302,820 (CAD) |
Organisation | Great Lakes Fishery Commission |
Sector | Public |
Country | United States |
Start | 01/2018 |
End | 12/2020 |
Description | NERC ACCE Doctoral Training Program |
Amount | £83,000 (GBP) |
Organisation | Natural Environment Research Council |
Sector | Public |
Country | United Kingdom |
Start | 10/2017 |
End | 04/2021 |
Description | NSF Postdoctoral Fellowship |
Amount | $207,000 (USD) |
Organisation | National Science Foundation (NSF) |
Sector | Public |
Country | United States |
Start | 01/2018 |
End | 12/2021 |
Description | Royal Society Research Grant |
Amount | £7,992 (GBP) |
Organisation | The Royal Society |
Sector | Charity/Non Profit |
Country | United Kingdom |
Start | 11/2017 |
End | 10/2018 |
Description | Sheffield Undergradaute Research Experience |
Amount | £1,230 (GBP) |
Organisation | University of Sheffield |
Sector | Academic/University |
Country | United Kingdom |
Start | 06/2017 |
End | 08/2017 |
Description | The genetic architecture of sexual dimorphism |
Amount | £5,032 (GBP) |
Organisation | Natural Environment Research Council |
Sector | Public |
Country | United Kingdom |
Start | 12/2019 |
End | 01/2020 |
Description | A talk or presentation - Invited departmental seminar at Imperial College London |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Postgraduate students |
Results and Impact | I was invited to give a departmental seminar to the Department of Life Sciences at Imperial College London. The visit increased the visibility of my research within the field of evolutionary biology and helped to establish new potential collaborations. |
Year(s) Of Engagement Activity | 2018 |
Description | A talk or presentation - Invited departmental seminar at University College London |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Other audiences |
Results and Impact | I was invited to give a departmental seminar. The visit increased the visibility of my research within the field of evolutionary biology and helped to establish new potential collaborations. |
Year(s) Of Engagement Activity | 2020 |
Description | A talk or presentation - Invited departmental seminar at University of Bath |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Other audiences |
Results and Impact | I was invited to give a departmental seminar. The visit increased the visibility of my research within the field of evolutionary biology and helped to establish new potential collaborations. |
Year(s) Of Engagement Activity | 2021 |
Description | A talk or presentation - Invited departmental seminar at University of Rochester, NY |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Other audiences |
Results and Impact | I was invited to give a departmental seminar. The visit increased the visibility of my research within the field of evolutionary biology and helped to establish new potential collaborations. |
Year(s) Of Engagement Activity | 2021 |
Description | Darwin's theory and DNA: Helping primary school children make the leap. I have established an interactive workshop covering fundamental principles of genetics and evolution for primary school students. This has been adapted into an educational package for home-schooling during the COVID19 pandemic. |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Schools |
Results and Impact | Darwin's theory and DNA: Helping primary school children make the leap' is a half-day workshop comprised of a series of practical activities to promote critical thinking skills and inquiry-based learning. First, each student learns what DNA is and how to extract it from their own cheek cells using everyday materials. I then demonstrate how evolution can generate the biological diversity around us using bird beaks as a fascinating real-life example. I use the classic Darwinian example of natural selection and provide students with life-size, 3D printed models of beaks of Darwin's finches. Students formulate hypotheses about how beak shape evolves and work in teams to devise ways of testing their hypotheses using measuring equipment. This workshop is grounded in educational research and widely applicable to students both nationally and internationally. In response to the COVID pandemic, I redesigned the workshop into an online home-schooling resource to meet the demands that the COVID pandemic placed on teachers and parents. This formed the basis of an MSc Science Communication dissertation in 2019/20. Between June - July 2020, the workshop had 1,098 users from 9 different countries. We targeted teachers at 8 local primary schools in Sheffield who were extremely positive about the workshop. The resources were chosen to feature on the Evolution Letters Editor's Blog and Evolution Learning Zone to showcase exceptional homeschooling resources. |
Year(s) Of Engagement Activity | 2020,2021 |
Description | Genetics & Evolution workshop at Elm Wood Primary School |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Geographic Reach | Regional |
Primary Audience | Schools |
Results and Impact | I have developed an 'Evolution & Genetics' workshop to teach students about avian evolutionary biology and genetics. Over the course of a morning, students extract DNA from their own cheek cells using a DNA pendant kit. They then conduct morphological examinations of 3D printed Darwin's finch beaks using callipers to illustrate evolutionary principles. The school reported increased interest in evolution and genetics. |
Year(s) Of Engagement Activity | 2019 |
Description | Invitation to give departmental seminar at Lyon University |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Postgraduate students |
Results and Impact | I was invited to give a departmental seminar to the Biometry and Evolutionary Biology Laboratory at Lyon University on 'Routes to the resolution of sexual conflict'. The visit increased my visibility within the field of evolutionary biology and helped to establish new potential collaborations. |
Year(s) Of Engagement Activity | 2017 |
Description | Invited departmental seminar at Lund University |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Postgraduate students |
Results and Impact | I was invited to give a departmental seminar to the Department of Biology at Lund University on 'Genomics of sexual dimorphism'. The visit increased my visibility within the field of evolutionary biology and helped to establish new potential collaborations. |
Year(s) Of Engagement Activity | 2018 |
Description | Invited departmental seminar at University of Manitoba |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Regional |
Primary Audience | Postgraduate students |
Results and Impact | I was invited to give a departmental seminar. The visit increased the visibility of my research within the field of evolutionary biology and helped to establish new potential collaborations. |
Year(s) Of Engagement Activity | 2019 |
Description | Invited departmental seminar at University of Nottingham |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Regional |
Primary Audience | Postgraduate students |
Results and Impact | I was invited to give a departmental seminar. The visit increased the visibility of my research within the field of evolutionary biology and helped to establish new potential collaborations. |
Year(s) Of Engagement Activity | 2020 |
Description | Invited plenary speaker at Annual EEB Colloquium, University of Toronto |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Postgraduate students |
Results and Impact | I was invited to give the 'Rising Star in Evolution' Plenary Talk. The visit increased the visibility of my research within the field of evolutionary biology and helped to establish new potential collaborations. |
Year(s) Of Engagement Activity | 2019 |
Description | Invited plenary speaker at GENECO Summer Meeting |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Postgraduate students |
Results and Impact | I was invited to give the plenary seminar at the meeting. The visit increased the visibility of my research within the field of evolutionary biology and helped to establish new potential collaborations. I also engaged with postgraduate students about their research and career plans. |
Year(s) Of Engagement Activity | 2019 |
Description | Invited speaker at workshop at Swedish Collegium for Advanced Study |
Form Of Engagement Activity | A formal working group, expert panel or dialogue |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Study participants or study members |
Results and Impact | I was invited to speak at the Swedish Collegium for Advanced Study on the workshop '"Bridging the gap between organismal and genomic views of sex differences". The visit increased my visibility within the field of evolutionary biology and helped to establish new potential collaborations. |
Year(s) Of Engagement Activity | 2018 |
Description | Invited to give departmental seminar at University of Edinburgh |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Postgraduate students |
Results and Impact | I was invited to give a departmental seminar to the Institute of Evolutionary Biology at the University of Edinburgh on 'Genomics of sexual dimorphism'. The visit increased my visibility within the field of evolutionary biology and helped to establish new potential collaborations. |
Year(s) Of Engagement Activity | 2017 |
Description | Organiser of Dept of Animal and Plant Sciences seminar series |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Postgraduate students |
Results and Impact | I organise the departmental seminar series at the University of Sheffield and invite selected speakers to visit the department. This acts to promote scientific discussion within the department and foster new and existing collaborations. |
Year(s) Of Engagement Activity | 2017,2018,2019,2020 |
Description | Participated in University of Sheffield Open Day |
Form Of Engagement Activity | Participation in an open day or visit at my research institution |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Public/other audiences |
Results and Impact | I engage with prospective undergraduates and parents at the University of Sheffield on Open Days. I take tours of students around the department and discuss the available courses and teaching. I highlight key themes from my research and use this to inspire an interest in genetics and evolutionary biology in the students. |
Year(s) Of Engagement Activity | 2017,2018 |
Description | Science blog |
Form Of Engagement Activity | Engagement focused website, blog or social media channel |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Media (as a channel to the public) |
Results and Impact | I contributed to a blog about my latest research (Battle of the sexes resolved, Evolution Letters Editor's blog). |
Year(s) Of Engagement Activity | 2018 |
URL | https://evolutionletters.wordpress.com/2018/02/10/battle-of-the-sexes-resolved/ |
Description | Speaker in Soapbox Science Sheffield |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Public/other audiences |
Results and Impact | I participated in SoapBox Science, a novel outreach event designed to increase the visibility of female scientists within the general public. |
Year(s) Of Engagement Activity | 2018 |
Description | Talk at Annual Meeting of the Anabantoid Association of Great Britain |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Public/other audiences |
Results and Impact | I gave a talk to members of the Anabantoid Association of Great Britain, a group of fish breeders and enthusiasts. They reported a greater understanding of the genetic mechanisms underpinning the great diversity of fish species. |
Year(s) Of Engagement Activity | 2019 |
Description | Tapton School Science Seminar, Sixth Form |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Regional |
Primary Audience | Schools |
Results and Impact | I gave a talk to Sixth Form students as part of the Tapton School Science Seminar. This talk was recorded for rewatching to ensure it reached a wide audience. The students were very engaged, and the talk sparked questions and discussion afterwards |
Year(s) Of Engagement Activity | 2020 |