Potential contribution of intrinsic developmental stability toward body plan conservation

Area of Science:

• Developmental Biology
• Evolutionary Biology
• Genomics

Background:

• Animal phyla exhibit conserved body plans despite morphological diversity.
• The phylotypic period is crucial for establishing body plans and is highly conserved across lineages.
• Mechanisms behind phylotypic period conservation are debated, with hypotheses including negative selection.

Purpose of the Study:

• To test the hypothesis that the phylotypic period's developmental stability drives body plan conservation.
• To investigate if reduced phenotypic variation potential during the phylotypic period explains evolutionary stasis.

Main Methods:

• Analysis of Japanese medaka embryos under controlled laboratory conditions.
• Measurement of whole embryonic transcriptome as a phenotype.
• Comparison of phenotypic differences between two wild medaka populations.

Main Results:

• The phylotypic period exhibits greater developmental stability than other embryonic stages.
• Genes expressed during the phylotypic period show less variation, even after environmental and mutational changes.
• Genes involved in cell signaling and morphological specification (e.g., Wnt, Hox) are enriched among stably expressed genes.

Conclusions:

• A strong correlation exists between developmental stability and evolutionary conservation during the phylotypic period.
• Developmental stability intrinsically limits phenotypic variation, potentially biasing evolutionary trajectories.
• This challenges the modern synthesis by highlighting the role of intrinsic organismal properties in shaping evolution.