Homology of process: developmental dynamics in comparative biology

Area of Science:

• Developmental biology
• Evolutionary biology
• Comparative genomics

Background:

• Comparative biology relies on homology, but homology for intermediate levels of organization (e.g., gene networks) is poorly defined.
• Existing definitions struggle with comparing developmental processes across species.

Purpose of the Study:

• To define homology for ontogenetic processes, distinct from gene or morphology homology.
• To establish criteria for comparing developmental processes like insect segmentation and vertebrate somitogenesis.

Main Methods:

• Investigated homology in insect segmentation and vertebrate somitogenesis.
• Proposed six criteria for process homology, integrating traditional indicators with dynamical systems modeling.
• Applied criteria to animal segmentation and other ontogenetic processes.

Main Results:

• Ontogenetic processes can be homologous even with divergent genes or gene networks, if their dynamics are conserved.
• Proposed criteria include sameness of parts, outcome, position, dynamical properties, complexity, and transitional forms.
• Demonstrated applicability of the criteria to animal segmentation.

Conclusions:

• Ontogenetic processes represent a distinct, comparable level of biological organization requiring specific homology criteria.
• A dynamical systems framework is crucial for rigorous comparison of complex, nonlinear developmental processes.
• This framework advances understanding of evolutionary developmental biology and related research programs.