Turtle body size evolution is determined by lineage-specific specializations rather than global trends

Area of Science:

• Paleontology
• Evolutionary Biology
• Macroevolutionary Studies

Background:

• Organisms exhibit diverse body sizes and shapes, with macroevolutionary studies investigating evolutionary dynamics.
• Turtles (Testudinata) display significant body size disparity, particularly considering their extensive fossil record.

Purpose of the Study:

• To explore body size evolution in turtles.
• To identify factors influencing observed body size patterns.
• To evaluate long-term directional trends in turtle body size evolution.

Main Methods:

• Compilation of a comprehensive turtle body size dataset.
• Correlation analysis with paleotemperature data.
• Estimation of ancestral body sizes.
• Macroevolutionary model-fitting analyses.

Main Results:

• No evidence for directional body size evolution (Cope's rule) in turtles was found.
• Paleotemperature did not significantly affect overall through-time body size patterns.
• Habitat preference significantly influenced turtle body size: freshwater turtles showed homogeneous size, terrestrial turtles trended larger, and marine turtles exhibited reduced size disparity post-Cenozoic.

Conclusions:

• Long-term, generalized macroevolutionary patterns in turtles are likely driven by group-specific factors, particularly habitat use.
• Habitat preference is a key determinant of body size evolution in turtles.
• Directional trends like Cope's rule do not appear to govern turtle body size evolution.