Data from: The physiological costs of prey switching reinforce foraging specialization

Sympatric speciation is thought to be strongly linked to resource
specialization with alternative resource use acting as a fundamental agent
driving divergence. However, sympatric speciation through niche expansion
is dependent on foraging specialization being consistent over space and
time. Standard metabolic rate is the minimal maintenance metabolic rate of
an ectotherm in a post-absorptive and inactive state and can constitute a
significant portion of an animal's energy budget; thus standard
metabolic rate and growth rate are two measures frequently used as an
indication of the physiological performance of individuals. Physiological
adaptations to a specific diet may increase the efficiency with which it
is utilized, but may have an increased cost associated with switching
diets, which may result in a reduced SMR and growth rate. In this study we
use the diet specialization often seen in polymorphic Arctic charr
(Salvelinus alpinus) populations to study the effects of different prey on
standard metabolic rate and growth rate as well as the effects that early
prey specialization may have on the ability to process other prey types
efficiently. We found a significant effect of prey type on standard
metabolic rate and growth rate. Furthermore, we found evidence of diet
specialization with all fish maintaining a standard metabolic rate and
growth rate lower than expected when fed on a diet different to which they
were raised, possibly due to a maladaptation in digestion of alternative
prey items. Our results show that early diet specialization may be
reinforced by the elevated costs of prey switching thus promoting the
process of resource specialization during the incipient stages of
sympatric divergence.