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Phenotypic and genetic correlation between male and female fitness in the simultaneous hermaphrodite Macrostomum lignano

Moosmann, Marvin (2017) BION01 20122
Degree Projects in Biology
Abstract
The relationship between the male and the female function in the simultaneous hermaphroditic flatworm Macrostomum lignano has been intensively studied on a phenotypic level. The results from these studies largely coincide with predictions that derive from sex allocation theory, which assumes a trade-off between the allocation of resources to the sex functions. Results from a recent experimental evolution study suggest that sexually antagonistic genetic variation could also have an impact on the correlation between male and female fitness. Sexually antagonistic genetic varia- tion manifests itself in a negative genetic correlation between male and female fitness and has so far mainly been described in separate-sexed organisms. This study... (More)
The relationship between the male and the female function in the simultaneous hermaphroditic flatworm Macrostomum lignano has been intensively studied on a phenotypic level. The results from these studies largely coincide with predictions that derive from sex allocation theory, which assumes a trade-off between the allocation of resources to the sex functions. Results from a recent experimental evolution study suggest that sexually antagonistic genetic variation could also have an impact on the correlation between male and female fitness. Sexually antagonistic genetic varia- tion manifests itself in a negative genetic correlation between male and female fitness and has so far mainly been described in separate-sexed organisms. This study investigates the phenotypic and genetic correlation between the male and female fitness components in M. lignano in two stressful environments; salt stress and food stress. The results suggest that there is no genetic or phenotyp- ic correlation between male and female fitness, despite considerable genetic variation in fitness for both sex functions. However, the residual variation shows a tendency for a negative correlation in a food-restricted environment, which could be an indication of a resource trade-off that is ob- scured on a phenotypic level by the genetic variation in fitness. It was further found that the genet- ic variances of both fitness functions are environment dependent. (Less)
Popular Abstract
Two sexes, one worm – insights into hermaphroditism

Evolutionary biology aims at understanding how the stunning diversity that surrounds us came to be. One particular aspect of life – sexual reproduction – comes in many shapes and forms. Yet, attention has mainly been focused on the system most familiar to us: separate sexed organisms. Understanding reproduction as a whole, however, re-quires leaving the comfort zone of well-known systems. In this study, I investigated a unique alternative reproductive mode: hermaphroditism.

Hermaphrodites combine both the male and the female function within one body. From re-search on separate sexed organisms it is known that the male and female function are not al-ways compatible; genes that... (More)
Two sexes, one worm – insights into hermaphroditism

Evolutionary biology aims at understanding how the stunning diversity that surrounds us came to be. One particular aspect of life – sexual reproduction – comes in many shapes and forms. Yet, attention has mainly been focused on the system most familiar to us: separate sexed organisms. Understanding reproduction as a whole, however, re-quires leaving the comfort zone of well-known systems. In this study, I investigated a unique alternative reproductive mode: hermaphroditism.

Hermaphrodites combine both the male and the female function within one body. From re-search on separate sexed organisms it is known that the male and female function are not al-ways compatible; genes that create a successful male can have negative effects on females. This raises the question if the situation in hermaphrodites is similar. I used the hermaphroditic flat-worm Marcrostomum lignano to investigate how the genetic basis of male fitness and female fit-ness are related. Previous studies that looked into the effects of the sex functions on each other in these worms did not focus on the genetics of this relationship. Knowledge of the genetic ba-sis of traits is however key to understanding their evolution.

I approached the question by assessing the number of offspring that worms produced via sperm and via eggs (male and female fitness respectively). A specific breeding design and statistical analysis then allowed me to estimate to what degree the genes determine the male and female fitness. Further, I could measure if a genetic background creating high male fitness leads to a low female fitness and vice versa. Because both the genetic contribution and the relationship between male and female fitness could be affected by the environmental conditions, I exposed worms to different treatments (salt stress, food stress, and a control).

The results demonstrate that genes, at least in part, determine whether an individual has a high or a low male or female fitness. Further, it turns out that the magnitude to which genes deter-mine male and female fitness depends on the environmental conditions. However, there is no genetic association between high male and high female fitness, i.e. a high male fitness does not imply high female fitness or vice versa. These results thus suggest that male and female fitness in this species can evolve independently.

Knowledge about the genetic basis of male and female fitness in hermaphrodites is a first step in understanding how evolutionary forces affect this alternative reproductive mode. This insight is not only of interest in the context of hermaphrodites. Understanding the differences and simi-larities between reproductive systems also helps us understand what makes our way of repro-duction, that we often take as a given, unique.

Master’s Degree Project in Biology, 45 credits, 2017
Advisor: Jessica Abbott
Department of Biology, Lund (Less)
Please use this url to cite or link to this publication:
author
Moosmann, Marvin
supervisor
organization
course
BION01 20122
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
8905920
date added to LUP
2017-04-19 15:27:01
date last changed
2017-04-19 15:27:01
@misc{8905920,
  abstract     = {The relationship between the male and the female function in the simultaneous hermaphroditic flatworm Macrostomum lignano has been intensively studied on a phenotypic level. The results from these studies largely coincide with predictions that derive from sex allocation theory, which assumes a trade-off between the allocation of resources to the sex functions. Results from a recent experimental evolution study suggest that sexually antagonistic genetic variation could also have an impact on the correlation between male and female fitness. Sexually antagonistic genetic varia- tion manifests itself in a negative genetic correlation between male and female fitness and has so far mainly been described in separate-sexed organisms. This study investigates the phenotypic and genetic correlation between the male and female fitness components in M. lignano in two stressful environments; salt stress and food stress. The results suggest that there is no genetic or phenotyp- ic correlation between male and female fitness, despite considerable genetic variation in fitness for both sex functions. However, the residual variation shows a tendency for a negative correlation in a food-restricted environment, which could be an indication of a resource trade-off that is ob- scured on a phenotypic level by the genetic variation in fitness. It was further found that the genet- ic variances of both fitness functions are environment dependent.},
  author       = {Moosmann, Marvin},
  language     = {eng},
  note         = {Student Paper},
  title        = {Phenotypic and genetic correlation between male and female fitness in the simultaneous hermaphrodite Macrostomum lignano},
  year         = {2017},
}