Evolution of metazoan morphological disparity

Area of Science:

• Evolutionary Biology
• Paleontology
• Genomics

Background:

• The animal kingdom displays vast morphological diversity (disparity).
• A key debate concerns whether maximal disparity was achieved early or if clades continually explore morphospace.
• Understanding the drivers of morphological evolution is crucial.

Purpose of the Study:

• To analyze the disparity of the animal kingdom throughout evolutionary history.
• To investigate whether major clades continually expand morphospace limits.
• To identify factors correlating with morphological expansion.

Main Methods:

• Analysis of morphological disparity across animal phyla.
• Examination of morphospace occupation throughout the Phanerozoic.
• Correlation analysis between disparity, genome size, and genetic factors.

Main Results:

• Major animal phyla (arthropods, chordates, annelids, echinoderms, mollusks) have continually expanded morphospace since the Cambrian.
• The current "clumpiness" of morphospace is due to extinction of intermediate forms.
• Morphological distance correlates with complexity, body size, and species diversity.
• Increasing morphological disparity strongly correlates with genome size and microRNA repertoire, but not protein domain diversity.

Conclusions:

• Metazoan disparity has been shaped by continuous exploration of morphospace and the evolution of gene regulation.
• Gene regulation and genome size are key factors in morphological expansion.
• The invasion of terrestrial environments may have further spurred disparity post-Cambrian.