The macroevolutionary dynamics of activity pattern in mammals: Primates in context

Area of Science:

• Evolutionary Biology
• Mammalogy
• Phylogenetics

Background:

• Most primates and mammals are either diurnal (active during the day) or nocturnal (active at night).
• Cathemerality, an activity pattern of being active both diurnally and nocturnally, occurs infrequently across mammals and primates.
• Understanding the evolutionary drivers of activity patterns is crucial for primate evolutionary history.

Purpose of the Study:

• To evaluate macroevolutionary hypotheses explaining the rarity of cathemerality in mammals.
• To test whether differential diversification (higher extinction) or differential state persistence (higher transition rates) explains the prevalence of activity patterns.

Main Methods:

• Phylogenetic analysis of 3013 mammal species based on activity patterns.
• Estimation of speciation, extinction, and transition rates between activity states using hidden-rates models.
• Comparison of diversification dynamics across diurnal, nocturnal, and cathemeral lineages.

Main Results:

• No consistent differences in diversification rates (speciation and extinction) were found among activity patterns.
• Strong support for differential state persistence: transition rates out of cathemerality are significantly higher than out of nocturnality.
• Diurnality shows unusual persistence in anthropoid primates and sciurid rodents due to low transition rates and high speciation.

Conclusions:

• The distribution of mammalian activity patterns is primarily shaped by differential state persistence, not differential diversification.
• High transition rates out of cathemerality explain its rarity compared to diurnality and nocturnality.
• The persistence of diurnality in primates, not higher extinction of cathemeral primates, explains the low frequency of cathemerality in this clade.