Linking morphology to behaviour
Uncovering the genetic basis of behavioural and morphological traits and
the factors influencing their evolution is undoubtedly of great
significance, yet this only provides one half of the story; it is one
thing to establish the mechanisms of evolution and their phenotypic
consequences, but another entirely to elucidate the functional link
between them. The associations between morphology and behaviour are
perhaps the best-studied of the three integrative pathways discussed
here as in a broad sense uncovering these associations is the express
goal of functional morphology (Wainwright, 1994). Several experimental
studies have addressed the functional significance of chondrichthyan
morphology (Wilga and Lauder, 2004a). As a result, the contribution of
structures such as the dorsal, caudal, and pectoral fins to locomotor
performance in elasmobranchs is relatively well understood (Maia and
Wilga, 2013; Wilga and Lauder, 2001; Wilga and Lauder, 2004b). There are
however several major limitations of this approach that constrain
integration between morphological and behavioural studies. This
experimental approach rarely captures ecologically relevant complex
behaviours, and where it does, influence of the laboratory setting on
expressed behaviour cannot be ruled out (Moore and Biewener, 2015).
Moreover, population and species-specific morphologies (Grover, 1972;
Keeney and Heist, 2006; Sternes and Shimada, 2020) mean that there is
little reason to suggest that existing kinematic studies should be
representative of all – or even a substantial proportion of extant
chondrichthyan diversity. The lack of studies linking morphology to
complex behaviours in wild populations fundamentally constrains our
understanding of evolution as without such studies the true adaptive
value of morphology. This in turn constrains our understanding of
ecological interactions, the evolution of complex behaviours such as
foraging strategies, and how future environmental change may influence
them. Novel technological advancements are increasingly enabling
quantitative study of chondrichthyan behaviour in wild populations
(Butcher et al., 2021; Renshaw et al., 2023) and thus with sufficient
research effort this knowledge gap is likely to decrease, however
significant further study combining experimental and observational
approaches will be required in order to achieve this goal.