Data from: The behavioral origins of novelty: did increased aggression lead to scale-eating in pupfishes?

Behavioral changes in a new environment are often assumed to precede the
origins of evolutionary novelties. Here, we examined whether an increase
in aggression is associated with a novel scale-eating trophic niche within
a recent radiation of Cyprinodon pupfishes endemic to San Salvador Island,
Bahamas. We measured aggression using multiple behavioral assays and used
transcriptomic analyses to identify differentially expressed genes in
aggression and other behavioral pathways across three sympatric species in
the San Salvador radiation (generalist, snail-eating specialist, and
scale-eating specialist) and two generalist outgroups. Surprisingly, we
found increased behavioral aggression and differential expression of
aggression-related pathways in both the scale-eating and snail-eating
specialists, despite their independent evolutionary origins. Increased
behavioral aggression varied across both sex and stimulus context in both
species. Our results indicate that aggression is not unique to
scale-eating specialists. Instead, selection may increase aggression in
other contexts such as niche specialization in general or mate
competition. Alternatively, increased aggression may result from indirect
selection on craniofacial traits, pigmentation, or metabolism—all traits
which are highly divergent, exhibit signs of selective sweeps, and are
affected by aggression-related genetic pathways which are differentially
expressed in this system. In conclusion, the evolution of a novel
predatory trophic niche within a recent adaptive radiation does not have
clear-cut behavioral origins as previously assumed, highlighting the
multivariate nature of adaptation and the complex integration of behavior
with other phenotypic traits.