Facultative Transitions Have Trouble Committing, But Stable Life Cycles Predict Salamander Genome Size Evolution

Bonett, Ronald M.; Hess, Alexander J.; Ledbetter, Nicholus M.

doi:10.1007/s11692-020-09497-8

Cited by 8 publications

(35 citation statements)

References 69 publications

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“…130,154,156,159,160 Time limited developmental windows constrain genome size evolution and have led to macroevolutionary correlations between life cycle complexity and larger genome size. 130,156 Meaning, direct developing and paedomorphic salamanders have significantly higher optimal genome sizes compared to biphasic species. 130 The life cycle of a biphasic amphibian is interrupted with an abrupt morphogenic shift (metamorphosis) that often corresponds with major habitat transitions.…”

Section: Genome Size Evolutionmentioning

confidence: 99%

“…130,156 Meaning, direct developing and paedomorphic salamanders have significantly higher optimal genome sizes compared to biphasic species. 130 The life cycle of a biphasic amphibian is interrupted with an abrupt morphogenic shift (metamorphosis) that often corresponds with major habitat transitions. 31 The need for rapid development in ephemeral environments has been suggested as a reason why some biphasic amphibians maintain a relatively small genome size.…”

Section: Genome Size Evolutionmentioning

confidence: 99%

“…161,162 At the same time, lower developmental rate due to increased genome size may facilitate transitions to simple life cycles (direct developers and paedomorphs). 130,163,164 In salamanders, simpler life cycles permit genomic expansion which could have potential physiological advantages or could be a drift related process caused by relaxed selection, 165,166 or reduced mutational hazard. 167 Direct developing frogs do not show increases in genome size, 154,168 however they still transform at a very rapid rate inside of the egg (as fast as a couple of weeks in frogs compared to at least a couple of months in direct developing salamanders) 130 .…”

Section: Genome Size Evolutionmentioning

confidence: 99%

“…There is likely a connection between genome size and body size. Some of the largest obligately paedomorphic salamanders also have the largest genomes 130,145 . Within direct developing bolitoglossines there is a correlation between genome size and body size, suggesting some degree of interaction.…”

Section: Genome Size Evolutionmentioning

confidence: 99%

“…188 However, facultatively paedomorphic lineages have patterns of vertebral evolution that more closely resemble biphasic salamanders, 4 a consequence of frequently shifting between environments. 130 Whether or not losing an aquatic life cycle stage (direct development) increases the rate of evolution is trait dependent. Direct developers have a significantly higher rate of body form evolution compared to biphasic salamanders, but a significantly lower rate of limb evolution.…”

Section: Skeletal Evolutionmentioning

confidence: 99%

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Repeated ecological and life cycle transitions make salamanders an ideal model for evolution and development

Bonett

Ledbetter

Hess

et al. 2021

Developmental Dynamics

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Observations on the ontogeny and diversity of salamanders provided some of the earliest evidence that shifts in developmental trajectories have made a substantial contribution to the evolution of animal forms. Since the dawn of evo-devo there have been major advances in understanding developmental mechanisms, phylogenetic relationships, evolutionary models, and an appreciation for the impact of ecology on patterns of development (eco-evo-devo). Molecular phylogenetic analyses have converged on strong support for the majority of branches in the Salamander Tree of Life, which includes 764 described species. Ancestral reconstructions reveal repeated transitions between life cycle modes and ecologies. The salamander fossil record is scant, but key Mesozoic species support the antiquity of life cycle transitions in some families. Colonization of diverse habitats has promoted phenotypic diversification and sometimes convergence when similar environments have been independently invaded. However, unrelated lineages may follow different developmental pathways to arrive at convergent phenotypes. This article summarizes ecological and endocrine based causes of life cycle transitions in salamanders, as well as consequences to body size, genome size, and skeletal structure. Salamanders offer a rich source of comparisons for understanding how the evolution of developmental patterns has led to phenotypic diversification following shifts to new adaptive zones.

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