Modularity promotes morphological divergence in ray-finned fishes

Abstract

Modularity is considered a prerequisite for the evolvability of biological systems. This is because in theory, individual modules can follow quasi-independent evolutionary trajectories or evolve at different rates compared to other aspects of the organism. This may influence the potential of some modules to diverge, leading to differences in disparity. Here, we investigated this relationship between modularity, rates of morphological evolution and disparity using a phylogenetically diverse sample of ray-finned fishes. We compared the support for multiple hypotheses of evolutionary modularity and asked if the partitions delimited by the best-fitting models were also characterized by the highest evolutionary rate differentials. We found that an evolutionary module incorporating the dorsal, anal and paired fins was well supported by the data, and that this module evolves more rapidly and consequently generates more disparity than other modules. This suggests that modularity may indeed promote morphological disparity through differences in evolutionary rates across modules.

Integration and modularity of teleostean pectoral fin shape and its role in the diversification of acanthomorph fishes

“…; Felice and Goswami ; Larouche et al. ). However, others have found relatively little association between integration and evolutionary trends (Goswami and Polly ; Sanger et al.…”

“…Thus far, empirical studies suggest that the relationship between integration, modularity, morphological variance (disparity), and evolutionary rate varies between systems. Some studies have demonstrated an association between increased modularity and/or decreased integration with greater morphological disparity and/or rates of evolution (Claverie and Patek 2013;Goswami et al 2015;Felice and Goswami 2018;Larouche et al 2018). However, others have found relatively little association between integration and evolutionary trends (Goswami and Polly 2010;Sanger et al 2012;Gerber 2013), or even positive correlations between morphological integration and disparity (Randau and Goswami 2017).…”

A critical appraisal of appendage disparity and homology in fishes

“…Fins are functionally important for locomotion, yet they are also evolutionarily labile structures that can generate high levels of morphological disparity, notably among ray-finned fishes (Larouche, Zelditch, & Cloutier, 2018). The morphological and functional disparity of fish appendages, the quality of the fossil record and the paraphyly of fishes all complicate inferring homologies of fins.…”

Comparing the strength of modular signal, and evaluating alternative modular hypotheses, using covariance ratio effect sizes with morphometric data

“…The past several decades have seen resurging interest in understanding the evolution of modularity, and numerous analytical approaches have been developed for quantifying patterns of modularity in phenotypic datasets (e.g., Magwene 2001;Mitteroecker and Bookstein 2007;Márquez 2008;Klingenberg 2009;Adams 2016;Goswami and Finarelli 2016). Concomitant with these advances is an increasing number of empirical studies that characterize patterns of modularity in distinct phenotypic traits, and across a wide variety of taxa (for recent examples, see Parsons et al 2012;Parr et al 2016;Felice and Goswami 2018;Larouche et al 2018; Bardua et al 2019). Likewise, evolutionary biologists have striven to decipher whether patterns of modularity are similar among taxa and traits, and across levels of biological organization (Drake and Klingenberg 2010;Renaud et al 2012;Sanger et al 2012;Felice and Goswami 2018;Bardua et al 2019;Marshall et al 2019).…”