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Sexual selection and neo-sex chromosome evolution in the superfamily Sylvioidea

Lindqvist, Carl (2018) BIOM01 20172
Degree Projects in Biology
Popular Abstract
Competition over reproduction – how does it affect the DNA?

Competition over what is often a scarce resource -reproduction, is a phenomenon widely studied in science. It is the ultimate endeavor for life, ensuring that an individual’s DNA is carried on to the next generation, preserving its footprint in the shape of a child. This is a very selfish enterprise for many organisms which becomes apparent when one observes what is called intersexual competition, which is competition between the two sexes for reproduction. An example of this is in many species of praying mantis; where the female not only considers a male a mate but also a snack and will bite of the head of the male during the act of sex and slowly consume him. Luckily the male... (More)
Competition over reproduction – how does it affect the DNA?

Competition over what is often a scarce resource -reproduction, is a phenomenon widely studied in science. It is the ultimate endeavor for life, ensuring that an individual’s DNA is carried on to the next generation, preserving its footprint in the shape of a child. This is a very selfish enterprise for many organisms which becomes apparent when one observes what is called intersexual competition, which is competition between the two sexes for reproduction. An example of this is in many species of praying mantis; where the female not only considers a male a mate but also a snack and will bite of the head of the male during the act of sex and slowly consume him. Luckily the male has a strategy to still ensure that his one goal in life is fulfilled and has adapted to this ritual by acquiring a second brain in his abdomen just to complete the fertilization. There is also what is termed intrasexual competition which is instead carried out within one sex for reproduction. One example for such competition is in the long-tailed widowbird where the males compete for females through having grossly oversized tailfeathers. The longer their tailfeathers are the more successful the male will be in procuring mates. However, imagine how much more difficult it becomes for the male to carry out every other aspect of life with tailfeathers that are three times the length of his body. We have observed how sexual competition affects the behavior and appearance of organisms for many years. Yet how it shapes the DNA there is little empirical evidence for.

I’ve made a two-pronged engagement on this question. The first approach was to find a suitable system to study. It so happens that a superfamily of birds called Sylvioidea has a very interesting characteristic in their DNA called a neo-sex chromosome “a new sex chromosome”. This new sex chromosome is young enough relative to the good old sex chromosomes to allow for the observation that sexual competition has on it. Through rigorous work I found pairs of species from the Sylvioidea superfamily where each pair fulfilled the following criteria; they were closely related, each species had different levels of sexual competition relative to each other and they were not to rare or too hard to acquire samples from. This word resulted in a list of 13 species pairs.

The second approach of the study was to develop a proof of concept method on how to analyze these neo-sex chromosomes. This was done for future research to provide a method at which to analyze the list of species pairs that I explainer above. In this approach I used a species of bird called the Great Reed Warbler that is a part of the Sylvioidea superfamily. I decided to analyze a number of genes that were evenly distributed across its neo-sex chromosome, each gene with the potential to produce one or more different proteins. I then analyzed the same genes in another bird where they still resided on the regular chromosomes to see much change they had undergone in the Great Reed Warbler since they became a neo-sex chromosome.

I statistically analyzed my list of 13 species pairs to see if there would be any connections between plumage scores and how these species mated. This because different modes of mating can suggest different levels of sexual competition. There was however no clear patterns. The results I got from the analysis of the DNA was not along the expectations that I had, yet they were very interesting. They furthered my understanding of how changes occur on the sex chromosomes. In addition I got many useful insights on how to conduct future studies in this field. However, to investigate how sexual competition acts on the DNA I would have to use the proof of concept method on the list that I made. Future studies are required to get further answers on this topic. Yet I believe we’ll uncover much more in this field in the years to come. Furthering our understanding of the genome, of DNA which is the very building blocks of life will have an almost infinite number of applications in science.

Master Degree Project in Biology, 30 hp, Department of Biology, Lund University,

Advisor: Professor Bengt Hansson, Department of Biology, Lund University. (Less)
Please use this url to cite or link to this publication:
author
Lindqvist, Carl
supervisor
organization
course
BIOM01 20172
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
8958633
date added to LUP
2018-09-13 12:18:32
date last changed
2018-09-13 12:18:32
@misc{8958633,
  author       = {Lindqvist, Carl},
  language     = {eng},
  note         = {Student Paper},
  title        = {Sexual selection and neo-sex chromosome evolution in the superfamily Sylvioidea},
  year         = {2018},
}