Topological and variational modularity: A case study using the pectoral girdle across the Chrosomus eos-neogaeus...

Area of Science:

• Evolutionary developmental biology (Evo-Devo)
• Comparative anatomy
• Morphological evolution

Background:

• Modularity and integration are crucial for evolvability in developmental evolution research.
• Geometric morphometrics (GMM) is commonly used, but anatomical network analysis (AnNA) is emerging.
• AnNA's utility for within-taxa variability and comparison with GMM remains underexplored.

Purpose of the Study:

• To compare AnNA and GMM for assessing modularity and integration within the Chrosomus eos-neogaeus hybridization complex.
• To evaluate AnNA's potential for hypothesis generation in understudied taxa.
• To determine the best practices for utilizing AnNA and GMM in skeletal analysis.

Main Methods:

• Utilized landmark-based geometric morphometrics (GMM).
• Employed anatomical network analysis (AnNA) to study pectoral girdle morphology.
• Investigated the Chrosomus eos-neogaeus hybridization complex as a model system.

Main Results:

• Pectoral girdle anatomy showed limited variation, but bone morphology and sutures exhibited significant diversity.
• C. neogaeus featured enlarged, fused bones, while C. eos had gracile, unfused elements; hybrids displayed distinct morphologies.
• AnNA identified modularity patterns, and GMM supported similar modularity but revealed different variation trajectories.

Conclusions:

• AnNA is valuable for generating novel hypotheses in understudied taxa, which can be tested with GMM.
• Morphological descriptions of skeletal systems enhance the interpretation of both AnNA and GMM.
• Combining AnNA and GMM provides a robust approach to studying morphological evolution and modularity.