Populations respond to their local environment through local adaptation and phenotypic plasticity. It is
increasingly evident that locally adapted genetic differences may not be the only source of adaptive local
responses. Heritable epigenetic marks and microbiome composition may also raise local phenotypic
responses that could be adaptive. This thesis investigates potentially adaptive plastic responses and
population specific patterns in molecular and non-genetic phenotypes in response to temperature in the
social spider species Stegodyphus dumicola. First, the molecular basis is established in chapter 1. Second, I
highlight a range of candidate genetic, DNA methylation and microbiome variants likely to be involved in
responses to the local climate in chapter 2. Third, plastic and population specific phenotypic responses to
temperature is further investigated in a range of molecular and non-genetic phenotypes using a multiple
common garden setup.
Chapter 1 contains the first published methylome in chelicerates, the reference genome for Stegodyphus
dumicola, and the indication that DNA methylation in gene bodies may influence gene expression in
spiders. Inferred evidence furthermore suggest that DNA methylation is relatively conserved in
chelicerates. This chapter has been published in “Genes”.
Chapter 2 is currently under review in “Molecular ecology” and investigates genetic, DNA methylation and
microbial symbiont variation in relation to climatic variation. The results suggest that both genetic
adaptation as well as plasticity, mediated by non-genetic mechanisms, may underlie local responses to the
environment.
Chapter 3 investigates population specific and plastic responses to temperature in a multiple common
garden setup. The phenotypes under investigation are both molecular and non-genetic and include
temperature tolerances, DNA methylome, transcriptome, metabolome and microbiome. The study reveal
population specific plastic responses in temperature tolerances, and we found candidate variants from all
investigated phenotypes potentially underlying such phenotypic responses. Exploration of the relationship
between gene-body methylation and gene expression return equivocal results, rendering the function of
gene-body DNA methylation in spiders unclear. This chapter is a manuscript in preparation.

In summary, this thesis brings insight into the fields of adaptation and plasticity by enlightening the
potential for non-genetic local responses as factors shaping the phenotype.