Simon Jacobsen Ellerstrand

Doctoral Student

Research areas and keywords

UKÄ subject classification

  • Biological Sciences

Research

As a master student I developed an interest in the field of evolutionary ecology and population genetics. I joined several projects on bumblebees in the Swedish agricultural landscape, as either a field or lab assistant. For my Master project I studied the post-glacial migration and refugia of the Red Vanilla orchid (Nigritella miniata). After graduation I worked for half a year as a bioinformatics assistant, studying the population genomics of the European spruce bark beetle (Ips typographus) before starting my doctoral studies.

My doctoral studies will focus on the ecology and evolution of male and female genes and genomes. I will focus on the systems (i) Sylvioidea birds and (ii) bumblebees:

i) Sex chromosomes are believed to evolve when an autosome gains a sex determining mutation, which in turn favours linkage of other sex-specific genes around that locus. With time recombination is suppressed in the heterogametic sex to ensure that these sex related genes are inherited together. Over time, sex chromosomes take on some characteristics such as degeneration and gene loss through accumulation of deleterious mutations on the sex-limited chromosome (Y or W), and dosage compensation in the heterogametic sex. In the passerine superfamily Sylvioidea there have recently been several neo-sex chromosomes discovered, some which are shared by all families, some which are unique to a few families, within Sylvioidea. The time range of these chromosome fusions provides me with a system to study several steps in sex chromosomes evolution in relation to demography, sexual selection, and environmental adaptations.

ii) In haplodiploid Hymenopteran, females are diploid and develop from fertilised eggs, while males are haploid and develop from unfertilised eggs. Sex determination in itself is believed to be caused through complementary sex determination at the CSD locus. Heterozygotes at this locus become female, while homozygous diploids and hemizygotes become male. A fitness benefit of this system should be resilience to inbreeding depression as recessive deleterious alleles may be purged through expression in the haploid male. However, reduced allelic diversity at the CSD locus could result in involuntary production of diploid homozygous males that do not contribute resources to the colony, therefore reducing its fitness. While the CSD locus is well characterised in the honeybee, it is not yet so in bumblebees. In my studies I will try to locate and describe the CSD locus in bumblebees, as well as study it in relation to population health. I will approach this topic through studies of wild populations of bumblebees and through demographic modelling, with the aim to further improve conservation efforts of declining, wild bumblebee populations.