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.研究背景：脊椎动物中被广泛认可的生态形态学关系之一，为肠道长度与日粮中动物猎物占比呈负相关。尽管多数鱼类类群符合这一普遍规律，但其他演化支仅表现出极微弱的关联，部分类群甚至呈现相反的趋势。此外，该关系及其演化起源尚未从系统发育视角得到充分关注。本研究基于28种鯻科（Terapontidae，俗称鼓鱼）鱼类的分子系统发育树，记录了该类群肠道长度变异的系统发育演化历程，及其与食性的关联。鯻科是一类起源于广盐性海洋环境的类群，也是澳大利亚淡水鱼类科中营养生态位多样性最高的类群，自其侵入淡水环境以来，已广泛发生了食性从以动物猎物为主的转变。 研究结果：本研究对鯻科鱼类肠道复杂度的个体发育过程进行描述，并结合祖先性状状态重建，发现复杂的肠道环化（卷曲）在该科内曾多次独立演化。这一个体发育模式的改变，正是造成鯻科鱼类肠道长度种间差异的主要驱动因素。基于系统发育的比较分析（系统发育独立对比，phylogenetic independent contrasts）结果显示，由上述个体发育机制所导致的肠道长度种间差异，可解释鯻科鱼类日粮中动物源性物质占比约65%的变异。 研究结论：肠道复杂度的个体发育过程，似乎是澳大利亚淡水鯻科鱼类广泛营养分化的重要功能创新，尤其推动了该科类群从肉食性（涵盖无脊椎动物与脊椎动物）食性的显著转变。改造肠道形态与生理的能力，或许也是其他类群辐射演化过程中促进营养生态位分化的关键因素。