Developmental constraints and the evolution of terrestrial reproductive modes in Anura

• Applicants: Privatdozent Dr. Hendrik Müller; Dr. Benjamin Naumann
• Subject Area: Evolutionary Cell and Developmental Biology (Zoology)
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 563588454

What role do developmental constraints play in evolution? This is still a central question in evolutionary developmental biology. Developmental constraints usually result from interactions between developmental processes and canalise ontogenetic and evolutionary processes. These constraints can be essential for understanding evolutionary patterns. However, their identification is not always clear due to the dynamics of developmental processes. In this project, the role of constraints during the multiple independent evolution (convergent evolution) of direct development and other derived forms of biphasic development in different anuran groups will be investigated. In addition to developmental constraints, adaptations can also be identified. Originally, the reproduction of anurans (and amphibians in general) comprises aquatic eggs that develop into aquatic, free-swimming and feeding larvae. These undergo a thyroid hormone-dependent metamorphosis into a near-terrestrial adult. This original mode of reproduction has been considerably modified in different amphibian groups, from fully aquatic to terrestrial eggs, a terrestrial larval phase, direct development and viviparity. However, the independent evolution of derived reproductive modes contradicts the general idea that metamorphosis, as a complex, neuroendocrine-regulated process, limits the evolvability of anuran ontogeny. The overarching questions of this project are therefore: Is metamorphosis an ontogenetic phase that is subject to strong constraints and controls the evolvability of terrestrial reproductive forms in anurans? Which developmental biological pattern-forming processes (heterochrony, heterometry, heterotopy, heterotypy) are involved in the evolution of terrestrial reproductive forms? Is the developmental reorganisation of neural structures in anurans dependent on the activity of the brain-pituitary-thyroid axis? We aim to address these questions by analysing diverse aspects of nervous system development in the currently largest dataset of anurans with different reproductive modes and varying degrees of terrestrial development. This will be achieved through a combination of histology, micro-computed tomography, 3D reconstruction, morphometric methods and heterochrony analyses. The data from this project will be combined with existing or in parallel acquired data on the development of other organ systems to obtain an organismic view of the development of anurans. The result will be both a comprehensive insight into the evolution of anuran developmental processes and a greater understanding of the role of developmental constraints in their reorganisation.

• DFG Programme: Research Grants