Non-parallel yet strong genomic footprints of divergent
selection between urban and forest populations and evidence for
polygenic adaptation
First, Bayescan identified 15 outliers for Barcelona, 11 for Montpellier
and 10 for Warsaw, distributed across 15 chromosomes and associated with
13 genes in 5kb upstream or downstream regions (Figure 4, q-value
< 0.1, see Figure S1). None of these outliers was shared
between the three population pairs, revealing no convergence between
cities. Second, the multivariate approach based on an RDA revealed a
list of 1163 loci with outlier loading score (Figure S2) suggesting a
high number of loci putatively undergoing weaker selection. These 1163
loci were associated with 561 genes.
GO analyses revealed the existence of overrepresented ontologies (P
< 0.05 and at least 3 genes per GO). Among the most promising
GO terms we found functions related to the nervous system (GO:0048846,
axon extension involved in axon guidance; GO:0035418 protein
localization to synapse; GO:0021987 cerebral cortex development;
GO:0007274, neuromuscular synaptic transmission), the blood system
(GO:0045777 positive regulation of blood pressure; GO:0042311,
vasodilatation), hormonal response (GO:0071277, cellular response to
estrogen stimuli) and stress response (GO:0033555, multicellular
response to stress), revealing potential important functions involved in
adaptation to urban habitats. Detailed GO results are presented in SI
Table S8 and Figure S3.