Data from: Ontogenetic development of intestinal length and relationships to diet in an Australasian fish family (Terapontidae)

Background: One of the most widely accepted ecomorphological relationships
in vertebrates is the negative correlation between intestinal length and
proportion of animal prey in diet. While many fish groups exhibit this
general pattern, other clades demonstrate minimal, and in some cases
contrasting, associations between diet and intestinal length. Moreover,
this relationship and its evolutionary derivation have received little
attention from a phylogenetic perspective. This study documents the
phylogenetic development of intestinal length variability, and resultant
correlation with dietary habits, within a molecular phylogeny of 28
species of terapontid fishes. The Terapontidae (grunters), an ancestrally
euryhaline-marine group, is the most trophically diverse of
Australia's freshwater fish families, with widespread shifts away
from animal-prey-dominated diets occurring since their invasion of fresh
waters. Results: Description of ontogenetic development of intestinal
complexity of terapontid fishes, in combination with ancestral character
state reconstruction, demonstrated that complex intestinal looping
(convolution) has evolved independently on multiple occasions within the
family. This modification of ontogenetic development drives much of the
associated interspecific variability in intestinal length evident in
terapontids. Phylogenetically informed comparative analyses (phylogenetic
independent contrasts) showed that the interspecific differences in
intestinal length resulting from these ontogenetic developmental
mechanisms explained ~65% of the variability in the proportion of animal
material in terapontid diets. Conclusions: The ontogenetic development of
intestinal complexity appears to represent an important functional
innovation underlying the extensive trophic differentiation seen in
Australia's freshwater terapontids, specifically facilitating the
pronounced shifts away from carnivorous (including invertebrates and
vertebrates) diets evident across the family. The capacity to modify
intestinal morphology and physiology may also be an important facilitator
of trophic diversification during other phyletic radiations.