THE MICRO AND MACRO IN BODY SIZE EVOLUTION

Area of Science:

• Evolutionary biology
• Ecology
• Paleontology

Background:

• Organism body size diversity is traditionally explained by microevolution (natural selection) or macroevolution (species selection).
• Logarithmic body mass distributions for terrestrial mammals and birds are skewed towards larger sizes.
• Understanding the drivers of these body size distributions is key to evolutionary studies.

Purpose of the Study:

• To evaluate the sufficiency of macroevolutionary and microevolutionary processes in explaining skewed body mass distributions.
• To investigate the roles of cladogenesis and anagenesis in body size evolution.
• To determine the influence of environmental factors on body size diversification.

Main Methods:

• Utilized simulation models to test evolutionary hypotheses.
• Simulated cladogenetic processes with varying extinction and speciation rates.
• Incorporated anagenetic size change within species into simulation models.

Main Results:

• Purely cladogenetic simulations without size bias did not produce skewed body mass distributions.
• Simulations including size-biased extinction rates, particularly with anagenetic change, consistently generated skewed distributions.
• Body size distributions varied across different island and continental environments.

Conclusions:

• Both cladogenetic and anagenetic processes are significant in body size evolution.
• Environmental conditions influence body size diversification through macro- and microevolutionary mechanisms.
• Macroevolution and microevolution are interconnected and not independent processes.