An integrated view of precambrian eumetazoan evolution.

Area of Science:

• Evolutionary biology
• Developmental biology
• Paleontology

Background:

• The eumetazoan clade, encompassing modern animals like cnidarians and bilaterians, originated in the late Neoproterozoic.
• Evidence suggests stem group eumetazoans may have evolved before the Marinoan glaciation.

Purpose of the Study:

• To integrate diverse evidence, including paleontology, phylogeny, and gene regulatory networks, to understand early eumetazoan evolution.
• To reconstruct the gene regulatory network organization of preeumetazoans and their assembly into the eumetazoan regulatory apparatus.

Main Methods:

• Combined paleontological observations, molecular and morphological phylogeny, and paleoecological data.
• Analyzed gene regulatory network (GRN) structures underlying bilaterian body plan development.
• Reconstructed ancestral GRN organization and evolutionary assembly processes.

Main Results:

• Eumetazoan body plans are characterized by complex, hierarchically organized GRNs.
• GRN kernels canalize developmental fate, influencing downstream evolutionary trajectories and clade diversification.
• The evolutionary assembly of GRNs for basic eumetazoan body plans differed fundamentally from species-level evolution.

Conclusions:

• The hierarchical and multilayered nature of GRNs is key to understanding early animal evolution.
• GRN evolution provides a framework for explaining the rapid diversification of early animal clades.
• Genomic program evolution for body plan development represents a distinct evolutionary mechanism compared to microevolutionary changes.