Testing hypotheses of marsupial brain size variation using phylogenetic multiple imputations and a Bayesian...

Area of Science:

• Evolutionary biology
• Comparative neuroanatomy
• Mammalian evolution

Background:

• Mammalian brain size evolution is complex, with ongoing debate regarding key explanatory hypotheses and variables.
• Previous studies often focused on placental mammals, potentially overlooking unique evolutionary pressures in other groups like marsupials.

Purpose of the Study:

• To investigate the primary drivers of brain size variation in marsupials.
• To compare the factors influencing brain size evolution between marsupials and placental mammals.

Main Methods:

• Utilized a novel, high-coverage dataset of marsupial brain and body sizes.
• Employed phylogenetically imputed datasets for 16 predictor variables.
• Applied phylogenetically corrected Bayesian generalized linear mixed-effects modeling.

Main Results:

• Litter size was identified as the sole significant predictor of brain size variation in marsupials.
• Marsupials exhibit less reproductive trait diversity compared to placental mammals.
• Reproductive traits in placentals may confound associations between behavioral/ecological factors and brain size.

Conclusions:

• Reproductive traits, specifically litter size, play a critical role in marsupial brain size evolution.
• Future studies on placental mammals should account for reproductive parameters like litter size, gestation, and weaning age.
• The distinct reproductive strategies between marsupials and placentals likely influence the observed differences in brain size predictors.