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Wolbachia presence in the damselfly Ischnura elegans: a recent selective sweep leading to high infection levels and low mitochondrial diversity?

Deng, Junchen (2020) BION02 20192
Degree Projects in Biology
Popular Abstract
Bacterial invasion of a damselfly reduces genetic diversity

Wolbachia is a common bacterium that lives in the cells of a great diversity of insects. This bacterium is a great manipulator of insect biology. In the blue moon butterfly (Hypolimnas bolina), Wolbachia kills male embryos so there is as little as one male blue moon for a staggering one hundred females. Additionally, in some species of wood lice, Wolbachia can even transform male embryos into females, enabling greater maternal transmission.

Similar to the cell’s mitochondria (a powerhouse organelle that contains its own DNA), Wolbachia is also strictly inherited from mother to offspring. This feature links Wolbachia to host mitochondria between generations. Imagine an insect... (More)
Bacterial invasion of a damselfly reduces genetic diversity

Wolbachia is a common bacterium that lives in the cells of a great diversity of insects. This bacterium is a great manipulator of insect biology. In the blue moon butterfly (Hypolimnas bolina), Wolbachia kills male embryos so there is as little as one male blue moon for a staggering one hundred females. Additionally, in some species of wood lice, Wolbachia can even transform male embryos into females, enabling greater maternal transmission.

Similar to the cell’s mitochondria (a powerhouse organelle that contains its own DNA), Wolbachia is also strictly inherited from mother to offspring. This feature links Wolbachia to host mitochondria between generations. Imagine an insect population that is unfortunately invaded by Wolbachia, the linked mitochondrial genotype will hitch a ride to a dominance as Wolbachia takes over the population. The overall genetic diversity of host mitochondria will therefore be reduced.

We discovered that three new Wolbachia strains were present in the blue-tailed damselfly (Ischnura elegans) that had their DNA extracted. Samples from different countries showed that Wolbachia has invaded several populations in the northwestern Europe. In Sweden, the populations were overwhelmed with the bacterium, reaching a surprisingly high infection frequency of 0.977. Such a rampage of Wolbachia indicates a potential role that this bacterium played in the biology of the common bluetail.

When investigating the genetic diversity of mitochondrial COI gene of I. elegans. A pattern came to light. The genetic diversity of host mitochondria was significantly reduced in populations infected by a common Wolbachia strain, while was maintained in the uninfected populations. If the invasion of Wolbachia is continuing, the uninfected populations would be doomed to a loss of genetic diversity similar to the infected ones. If the infection gets a chance to invade a closely-related species, the mitochondrial DNA would be homogenized, which will blur the border between species.

The story between Wolbachia and the blue-tailed damselfly that we have shown so far is just the tip of the iceberg. As a great invertebrate manipulator, Wolbachia may have changed the biology of the common bluetail in many other ways. This brings to mind many subsequent research questions: for example, how Wolbachia affects the biology of I. elegans? What feature allows Wolbachia to spread across populations of I. elegans? Why Wolbachia disappears in some populations? The story behind the bacterium and the damselfly will be unfolding in the near future.

Master’s Degree Project in Animal Ecology, 120 credits, 2020
Department of Biology, Lund University

Advisor: Dr. Anne Duplouy, Prof. Erik Svensson
Department of Biology, Lund University (Less)
Please use this url to cite or link to this publication:
author
Deng, Junchen
supervisor
organization
course
BION02 20192
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
9015152
date added to LUP
2020-06-09 14:34:26
date last changed
2020-06-09 14:34:26
@misc{9015152,
  author       = {Deng, Junchen},
  language     = {eng},
  note         = {Student Paper},
  title        = {Wolbachia presence in the damselfly Ischnura elegans: a recent selective sweep leading to high infection levels and low mitochondrial diversity?},
  year         = {2020},
}