Adult frogs and tadpoles have different macroevolutionary patterns across the Australian continent

• Published in: Nature ecology & evolution Vol. 1; no. 9; pp. 1385 - 1391
• Main Authors: Sherratt, Emma, Vidal-García, Marta, Anstis, Marion, Keogh, J. Scott
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.09.2017; Nature Publishing Group
• Subjects: 631/181; 631/181/2806; Amphibians; Animals; Anura - anatomy & histology; Anura - growth & development; Australia; Biological and Physical Anthropology; Biological Evolution; Biomedical and Life Sciences; Density; Developmental stages; Divergence; Ecology; Evolution; Evolutionary Biology; Frogs; Homoplasy; Juveniles; Larva - anatomy & histology; Larva - growth & development; Life cycles; Life Sciences; Metamorphosis; Metamorphosis, Biological; Morphology; Morphometry; Ontogeny; Paleontology; Phylogeny; Speciation; Zoology
• ISSN: 2397-334X
• DOI: 10.1038/s41559-017-0268-6

Developmental changes through an animal’s life are generally understood to contribute to the resulting adult morphology. Possible exceptions are species with complex life cycles, where individuals pass through distinct ecological and morphological life stages during their ontogeny, ending with metamorphosis to the adult form. Antagonistic selection is expected to drive low genetic correlations between life stages, theoretically permitting stages to evolve independently. Here we describe, using Australian frog radiation, the evolutionary consequences on morphological evolution when life stages are under different selective pressures. We use morphometrics to characterize body shape of tadpoles and adults across 166 species of frog and investigate similarities in the two resulting morphological spaces (morphospaces) to test for concerted evolution across metamorphosis in trait variation during speciation. A clear pattern emerges: Australian frogs and their tadpoles are evolving independently; their markedly different morphospaces and contrasting estimated evolutionary histories of body shape diversification indicate that different processes are driving morphological diversification at each stage. Tadpole morphospace is characterized by rampant homoplasy, convergent evolution and high lineage density. By contrast, the adult morphospace shows greater phylogenetic signal, low lineage density and divergent evolution between the main clades. Our results provide insight into the macroevolutionary consequences of a biphasic life cycle. Animals with complex life cycles experience different selection pressures across life stages. Here, the authors show drastically different morphologies and evolutionary histories of Australian frogs and their tadpoles, which suggest that they are evolving independently.