Chapter 9 Sex allocation/(ratio) distorters. Sex ratio distorters The ESS SR may differ between the...
-
date post
21-Dec-2015 -
Category
Documents
-
view
221 -
download
0
Transcript of Chapter 9 Sex allocation/(ratio) distorters. Sex ratio distorters The ESS SR may differ between the...
![Page 1: Chapter 9 Sex allocation/(ratio) distorters. Sex ratio distorters The ESS SR may differ between the point of view of different genes within an individualconflict.](https://reader035.fdocuments.net/reader035/viewer/2022062407/56649d545503460f94a30e6c/html5/thumbnails/1.jpg)
Chapter 9
Sex allocation/(ratio) distorters
![Page 2: Chapter 9 Sex allocation/(ratio) distorters. Sex ratio distorters The ESS SR may differ between the point of view of different genes within an individualconflict.](https://reader035.fdocuments.net/reader035/viewer/2022062407/56649d545503460f94a30e6c/html5/thumbnails/2.jpg)
Sex ratio distorters
• The ESS SR may differ between the point of view of different genes within an individual conflict over SR
• SR distorting elements:– Nuclear genes– Cytoplasmatic elements
![Page 3: Chapter 9 Sex allocation/(ratio) distorters. Sex ratio distorters The ESS SR may differ between the point of view of different genes within an individualconflict.](https://reader035.fdocuments.net/reader035/viewer/2022062407/56649d545503460f94a30e6c/html5/thumbnails/3.jpg)
Nuclear genesSex chromosome meiotic drive:
1. Y chromosome drive leads to male bias:Y chromosome only transmitted by males so a gene on Y that will lead to more male offspring will spread
2. X chromosome drive leads to female bias:X drive at the cost of Y
Spread slower
Commonly found in Diptera
More common than Y drive
QuickTime™ and a decompressor
are needed to see this picture.
QuickTime™ and a decompressor
are needed to see this picture.
Aedes aegypti
![Page 4: Chapter 9 Sex allocation/(ratio) distorters. Sex ratio distorters The ESS SR may differ between the point of view of different genes within an individualconflict.](https://reader035.fdocuments.net/reader035/viewer/2022062407/56649d545503460f94a30e6c/html5/thumbnails/4.jpg)
B chromosomes• Supernumerary chromosome, not required for fitness• Generally no effect on SR but:
– PSR in Nasonia vitripennis, only male offspring produced– Ultimate selfish element, ensures own transmission at cost of the rest
of the genome
QuickTime™ and a decompressor
are needed to see this picture.
QuickTime™ and a decompressor
are needed to see this picture.
![Page 5: Chapter 9 Sex allocation/(ratio) distorters. Sex ratio distorters The ESS SR may differ between the point of view of different genes within an individualconflict.](https://reader035.fdocuments.net/reader035/viewer/2022062407/56649d545503460f94a30e6c/html5/thumbnails/5.jpg)
Cytoplasmic genes• Only transmitted trough the
maternal line > selection for SR distortion
• Include mitochondria and micro-organisms (Wolbachia, cardinium)
• Several mechanism found to increase the amount of female offspring produced
QuickTime™ and a decompressor
are needed to see this picture.
![Page 6: Chapter 9 Sex allocation/(ratio) distorters. Sex ratio distorters The ESS SR may differ between the point of view of different genes within an individualconflict.](https://reader035.fdocuments.net/reader035/viewer/2022062407/56649d545503460f94a30e6c/html5/thumbnails/6.jpg)
Feminizers
• Override the nuclear sex determination
• Found in woodlice, mites, parasitoids and shrimp
• Frequency often lower than expected, might be caused by risk of producing intersexes
QuickTime™ and a decompressor
are needed to see this picture.
QuickTime™ and a decompressor
are needed to see this picture.
QuickTime™ and a decompressorare needed to see this picture.
![Page 7: Chapter 9 Sex allocation/(ratio) distorters. Sex ratio distorters The ESS SR may differ between the point of view of different genes within an individualconflict.](https://reader035.fdocuments.net/reader035/viewer/2022062407/56649d545503460f94a30e6c/html5/thumbnails/7.jpg)
Maternal Sex Ratio
• Influences the fertilization rate
• Found in some parasitoids
• Should rapidly spread to fixation QuickTime™ and a
decompressorare needed to see this picture.
QuickTime™ and a decompressor
are needed to see this picture.
QuickTime™ and a decompressorare needed to see this picture.
?
?
![Page 8: Chapter 9 Sex allocation/(ratio) distorters. Sex ratio distorters The ESS SR may differ between the point of view of different genes within an individualconflict.](https://reader035.fdocuments.net/reader035/viewer/2022062407/56649d545503460f94a30e6c/html5/thumbnails/8.jpg)
Male killers• Two types: early and late
– Early: resources allocated to sons can be used by daughters with related bacteria
– Late: males used as vectors for horizontal transfer
QuickTime™ and a decompressor
are needed to see this picture.
QuickTime™ and a decompressor
are needed to see this picture.
QuickTime™ and a decompressor
are needed to see this picture.
QuickTime™ and a decompressorare needed to see this picture.
![Page 9: Chapter 9 Sex allocation/(ratio) distorters. Sex ratio distorters The ESS SR may differ between the point of view of different genes within an individualconflict.](https://reader035.fdocuments.net/reader035/viewer/2022062407/56649d545503460f94a30e6c/html5/thumbnails/9.jpg)
Parthenogenesis induction
• In haplodiploids: unfertilized eggs develop into females
• Genome duplication
• Found in several insect taxaQuickTime™ and a
decompressorare needed to see this picture.
QuickTime™ and a decompressor
are needed to see this picture.
QuickTime™ and a decompressorare needed to see this picture.
QuickTime™ and a decompressor
are needed to see this picture.
![Page 10: Chapter 9 Sex allocation/(ratio) distorters. Sex ratio distorters The ESS SR may differ between the point of view of different genes within an individualconflict.](https://reader035.fdocuments.net/reader035/viewer/2022062407/56649d545503460f94a30e6c/html5/thumbnails/10.jpg)
Cytoplasmic incompatibility
• Not strictly SR distorter
• In haploids male unaffected
>leads to male biased SR
QuickTime™ and a decompressor
are needed to see this picture.
QuickTime™ and a decompressor
are needed to see this picture.
QuickTime™ and a decompressorare needed to see this picture.
QuickTime™ and a decompressor
are needed to see this picture.
/only males
![Page 11: Chapter 9 Sex allocation/(ratio) distorters. Sex ratio distorters The ESS SR may differ between the point of view of different genes within an individualconflict.](https://reader035.fdocuments.net/reader035/viewer/2022062407/56649d545503460f94a30e6c/html5/thumbnails/11.jpg)
Genomic imprinting
• Differential expression alleles dependent on parental origin
• Alleles from different backgrounds can disagree over SR
• Imprinting as a battle ground for conflict over SR
![Page 12: Chapter 9 Sex allocation/(ratio) distorters. Sex ratio distorters The ESS SR may differ between the point of view of different genes within an individualconflict.](https://reader035.fdocuments.net/reader035/viewer/2022062407/56649d545503460f94a30e6c/html5/thumbnails/12.jpg)
Spread of SR distorters
• Often not fixed in populations
• Possible explanation:– Balancing selection
• Reduced fertility/survival infected individuals• Sexual selection, avoiding infected individuals
– Suppressors• Sex chromosome linked• Autosomal: Fisherian selection
![Page 13: Chapter 9 Sex allocation/(ratio) distorters. Sex ratio distorters The ESS SR may differ between the point of view of different genes within an individualconflict.](https://reader035.fdocuments.net/reader035/viewer/2022062407/56649d545503460f94a30e6c/html5/thumbnails/13.jpg)
PSR• Spread dependent on fertilization rate
• It can only invade when FR > 0.5
–LMC causes female biased SR, but small patch size selects against PSR–Presence of MSR, although PSR selects against MSR
QuickTime™ and a decompressor
are needed to see this picture.
![Page 14: Chapter 9 Sex allocation/(ratio) distorters. Sex ratio distorters The ESS SR may differ between the point of view of different genes within an individualconflict.](https://reader035.fdocuments.net/reader035/viewer/2022062407/56649d545503460f94a30e6c/html5/thumbnails/14.jpg)
Male killing• Spread dependent on transmission rate
– High transmission: fixation, population extinction– Low transmission: intermediate frequency
• Resource reallocation among offspring• Survival cost• Mating preference• Selection for nuclear suppression because of
– Increase in fecundity– Fisherian advantage of rare sex
![Page 15: Chapter 9 Sex allocation/(ratio) distorters. Sex ratio distorters The ESS SR may differ between the point of view of different genes within an individualconflict.](https://reader035.fdocuments.net/reader035/viewer/2022062407/56649d545503460f94a30e6c/html5/thumbnails/15.jpg)
The consequences of SR distorters
1. Compensatory SR adjustmentOnly under imperfect transmission
Under high transmission, no selection
>no gene flow between infected and uninfected part population
![Page 16: Chapter 9 Sex allocation/(ratio) distorters. Sex ratio distorters The ESS SR may differ between the point of view of different genes within an individualconflict.](https://reader035.fdocuments.net/reader035/viewer/2022062407/56649d545503460f94a30e6c/html5/thumbnails/16.jpg)
Other effects of SR distorters• Sex role reversal, due to biased SR• The evolution of new sex determination
systems e.g haplodiploidy• Adjustment of breeding system e.g.
larger clutches, multiple mating, reallocation of resources among offspring
• Selective sweep, hitchhiking effect, reduced recombination (X drive)
![Page 17: Chapter 9 Sex allocation/(ratio) distorters. Sex ratio distorters The ESS SR may differ between the point of view of different genes within an individualconflict.](https://reader035.fdocuments.net/reader035/viewer/2022062407/56649d545503460f94a30e6c/html5/thumbnails/17.jpg)
Conclusion
• Main topics for future research:– What controls variation across taxa– The interplay between different distorters– Consequences for host biology
Lots of theory, but need for empirical data
![Page 18: Chapter 9 Sex allocation/(ratio) distorters. Sex ratio distorters The ESS SR may differ between the point of view of different genes within an individualconflict.](https://reader035.fdocuments.net/reader035/viewer/2022062407/56649d545503460f94a30e6c/html5/thumbnails/18.jpg)
Final thoughts
• Why so often in haplodiploids?
• Mechanisms: how does the drive work, details of mechanisms might influence effects