two PhD projects at the University of Edinburgh

two PhD projects at the University of
Edinburgh.
Advisory team: Dr. Laura Ross (Edinburgh), Dr. Konrad Lohse
(Edinburgh), Dr. Andy Gardner (st Andrews) and Dr. Lyn Cook (University
of Queensland)

Project 1: Intralocus sexual conflict and genome evolution in
haplodiploid organisms

Sexual conflicts result from a clash of interests between the sexes
[1]. In many cases, this battle is fought at the level of the gene:
males and females may differ with respect to which version of a gene
maximizes their Darwinian fitness. Whilst the effects of such
intralocus sexual conflicts have been studied intensively in many
organisms, the vast majority of studies have focused on species with
classical, diploid sexual reproduction. However, as many as 15% of
animal species exhibit an alternative, haplodiploid mode of
inheritance. In such species, mothers monopolize the production of male
offspring, either by asexual production of sons or by producing sons
that eliminate their father's genome after the zygote stage [2]. This
asymmetrical mode of inheritance is likely to affect the outcome of
intralocus sexual conflict. Specifically, as alleles that favour male
fitness cannot be passed on directly from fathers to sons, sexual
conflicts may be resolved in favour of females [2].

 The aim of this project is to study the fate of alleles under
intralocus sexual conflict in a range of haplodiploid taxa. Studying
such exceptions to the general rules of reproduction provides
illumination of the fundamental principles of evolutionary genetics
(see [3] for a recent comparable example).

 This project will combine laboratory experiments, gene expression
studies and genome analyses. We will focus particularly on springtails
and fungus gnats, as males in these species carry and express their
father's genomes, but do not pass them on to their offspring. In
addition, these species still retain recognizable sex chromosomes,
which enables informative sex chromosome / autosome comparisons (e.g.
[3] for a similar approach). These experimental approaches will be
combined with comparative phylogenetic analyses and the development of
novel evolutionary theory, according to the interests of the student.
The project is cosupervised by Dr. Gardner (University of St. Andrews)
a leading mathematical biologist whose works spans a wide range of
topics in theoretical biology and genetics. The proposed project
strongly rest upon this collaboration as, on the one hand,
formalization of the relevant theoretical hypotheses is currently
lacking and, on the other hand, empirical work is required for
estimation of key model parameters. The candidate will be based
primarily in Edinburgh, as required by the empirical work, but will
spend 1-2 days per month in St. Andrews for the duration of the
project, as well as two 1-2 month intensive visits to the Gardner lab
in years 2 and 3.

[1] Bonduriansky, Russell, and Stephen F. Chenoweth. "Intralocus sexual
conflict." Trends in Ecology & Evolution 24.5 (2009): 280-288.

[2] De la Filia, Andres G., Stevie A. Bain, and Laura Ross.
"Haplodiploidy and the reproductive ecology of Arthropods." Current
Opinion in Insect Science (2015).

[3] Jaquiry, Julie, et al. "Masculinization of the X chromosome in
the pea aphid." Plos Genet 9 (2013): e1003690.

Project 2: Sexual conflict and the loss of paternal genes in a group of
Australian insects

In thousands of insects reproduction involves "Genomic exclusion",
where males discard the chromosomes they inherited from their father
(Paternal Genome Elimination, PGE). This unusual type of reproduction
gives rise to sons that inherit genes from both their parents, but in
which genes inherited from their father are suppressed and eliminated.
As a result, males do never pass on any genes from their father
(Gardner & Ross, 2014; Ross et al.)  Until now, the lack of suitable
insect study systems has made it difficult to understand PGE: It is
absent in established model systems such as Drosophila and tends to be
evolutionarily conserved, making comparative studies difficult. However
we recently identified a group of Australian scale insects that vary in
the way they reproduce, with some species eliminating their father's
genes while others do not. This group therefore provides a rare chance
for acquiring new insights into the way this peculiar type of
reproduction evolved as well as the way it is accomplished.

The main questions addressed in the project are why and how males in
some species eliminate the genes they inherit from their fathers, while
others do not. Understanding this will give general insights into why
reproduction is so variable across the tree of life.

The proposed project will study the reproduction of a group of insects
that is found exclusively in Australia and feeds on eucalyptus trees.
The project on one hand will involve sampling and determining the
reproductive strategy of a large number of species as well as determine
ecological factors that might explain some of this variation. On the
other hand it will focus in more detail on a single genus of
Cystococcus (Semple et al. 2015, see figure 1), in which three species
vary in the presence of PGE. We will compare these three species using
a combination of genetic, genomic and cytogenetic approaches to
understand how and why they vary in their reproductive genetics.
Although primarily based at the University of Edinburgh, the project
will involve fieldtrips and labwork at the University of Queensland in
Australia, in collaboration with Dr. Lyn Cook.

-       Gardner, A. & Ross, L. (2014) Mating ecology explains patterns
of genome elimination Ecology Letters 17, 1602-1612.

-      Ross, L., Pen, I. & Shuker, D. M. (2010). Genomic conflict in
scale insects: the causes and consequences of bizarre genetic systems.
Biological Reviews 85, 807-828.
  * Semple, T., Gullan, P., Hodgson, C., Hardy, N., & Cook, L. (2015).
    Systematic review of the Australian. Invertebrate Systematics 29,
    287-312.

For informal enquiries contact Dr Laura Ross at laura.ross@ed.ac.uk.
Funding options are available for both UK and non-UK students but
deadlines vary so please get in touch asap.

Laura Ross