Compounding heterochrony shapes the salamander visual system across adaptive zones

Transitioning between disparate environments presents new physical challenges, and metamorphosis can provide solutions. The life cycles of most amphibians involve an aquatic-to-terrestrial transition and concomitant metamorphosis, but shifts in developmental timing (heterochrony) have also produced a wide variety of aquatic-only and terrestrial-only forms. Thyroid hormone signaling governs the timing of tissue transformation and may be a key mechanism behind the relationship between development and diversification of some metamorphic traits.  Here, we show that life-cycle mode and cave-adaptation (troglomorphy) through heterochrony primarily explain variation in salamander eyes and retina. Across levels of organization (organ/tissue), heterochrony led to serial reductions in the visual system of larval-form paedomorphs that lost metamorphosis. This pattern is compounded in larval-form paedomorphic lineages that subsequently transitioned to subterranean environments and evolved trog..., This database includes two files with data and one file with trees. Life cycle and habitat/ecological data were compiled from the literature and personal observations. Morphometric data are primarily external measurements. Retinal cell count data were from histological slides and published images. Names and codes for each variable are described in the README file. Posterior distribution of 1000 trees of 559 taxa was reconstructed in BEAST. See the associated manuscript and electronic supplemental document for additional methodological details, alternative regime models, and specimen numbers. , , # Compounding heterochrony shapes the salamander visual system across adaptive zones https://doi.org/10.5061/dryad.8931zcs04 This database includes: * one file with 1000 phylogenetic trees (chronograms). Life cycle and habitat/ecological data were compiled from the literature. Morphometric data are primarily external measurements. Retinal cell count data were from histological slides and published images. Posterior distribution of 1000 trees with 559 taxa was reconstructed in BEAST. * two data files containing the values used in phylogenetic comparative analyses * three files with base commands for BayesTraits, OUwie, PGLS, and Phylolm *See Manuscript and Electronic Supplemental Material for methodological details, alternative regime models, and specimen numbers. ### **TREES FILE: “1000_Chronograms_559_Salamander_lineages.tre”** A file with 1000 post-burnin Bayesian Chronograms of 559 salamander lineages. Names match those listed in the data files. ### DATA FILE: “Eye_Retina_dat...,