Data from: Killer whales (Orcinus orca) in Iceland show weak genetic structure among diverse isotopic signatures and observed movement patterns

Local adaption through ecological niche specialization can lead to genetic
structure between and within populations. In the Northeast Pacific, killer
whales (Orcinus orca) of the same population have uniform specialized
diets that are non-overlapping with other sympatric, genetically divergent
and socially isolated killer whale ecotypes. However, killer whales in
Iceland show intra-population variation of isotopic niches and observed
movement patterns: some individuals appear to specialise on herring and
follow it year-round while others feed upon herring only seasonally or
opportunistically. We investigated genetic differentiation among Icelandic
killer whales with different isotopic signatures and observed movement
patterns. This information is key for management and conservation purposes
but also for better understanding how niche specialization drives genetic
differentiation. Photo-identified individuals (N = 61) were genotyped for
22 microsatellites and a 611 bp portion of the mitochondrial control
region. Photo-identification of individuals allowed linkage of genetic
data to existing data on individual isotopic niche, observed movement
patterns and social associations. Population subdivision into three
genetic units was supported by a Discriminant Analysis of Principal
Components (DAPC). Genetic clustering corresponded to the distribution of
isotopic signatures, mtDNA haplotypes and observed movement patterns, but
genetic units were not socially segregated. Genetic differentiation was
weak (FST <0.1), suggesting ongoing gene flow or recent separation
of the genetic units. Our results show that killer whales in Iceland are
not as genetically differentiated, ecologically discrete or socially
isolated as the Northeast Pacific prey-specialized killer whales. If any
process of ecological divergence and niche specialization is taking place
among killer whales in Iceland it is likely at a very early stage and has
not led to the patterns observed in the Northeast Pacific.