Life history genomic regions explain differences in Atlantic salmon marine diet specialization

Abstract 1. Animals employ various foraging strategies along their
ontogeny to acquire energy, and with varying degree of efficiencies, to
support growth, maturation and subsequent reproduction events. Individuals
that can efficiently acquire energy early are more likely to mature at an
earlier age, as a result of faster energy gain which can fuel maturation
and reproduction. 2. We aimed to test the hypothesis that heritable
resource acquisition variation that co-varies with efficiency along the
ontogeny would influence maturation timing of individuals. 3. To test this
hypothesis, we utilized Atlantic salmon as a model which exhibit a simple,
hence trackable, genetic control of maturation age. We then monitored the
variation in diet acquisition (quantified as stomach fullness and
composition) of individuals with different ages, and linked it with
genomic regions (haploblocks) that were previously identified to be
associated with age-at-maturity. 4. Consistent with the hypothesis, we
demonstrated that one of the life history genomic regions tested six(6)
was indeed associated with age-dependent differences in stomach fullness.
Prey composition was marginally linked to six(6), and suggestively (but
non-significantly) to vgll3 genomic regions. We further showed Atlantic
salmon switched to the so-called “feast and famine” strategy along the
ontogeny, where older age groups exhibited heavier stomach content, but
that came at the expense of running on empty more often. 5. These results
suggest genetic variation underlying resource utilization may explain the
genetic basis of age structure in Atlantic salmon. Given that ontogenetic
diet has a genetic component and the strong spatial diversity associated
with these genomic regions, we predict populations with diverse maturation
age will have diverse evolutionary responses to future changes in marine
food-web structures. 28-Jul-2020