Multiple morphological clocks and total-evidence tip-dating in mammals

Area of Science:

• Evolutionary biology
• Paleontology
• Phylogenetics

Background:

• Morphological integration suggests correlated traits coevolve.
• Distinct suites of traits may evolve independently, like separate 'clocks'.

Purpose of the Study:

• To investigate if mammalian morphological data support multiple evolutionary clocks.
• To assess the impact of multi-clock models on divergence dating and phylogenetic inference.

Main Methods:

• Analyzed a large morphological dataset for mammals.
• Applied total-evidence tip-dating using multiple evolutionary clocks.
• Compared multi-clock analyses with single-clock and molecular clock models.

Main Results:

• Identified seven distinct morphological clocks in mammals, separate from the molecular clock.
• Multi-clock dating inflated divergence estimates but improved phylogenetic accuracy.
• Corrected the placement of meridiungulates and condylarths within placental mammals.

Conclusions:

• Multiple, distinct evolutionary clocks operate within mammalian morphology.
• Multi-clock approaches are feasible and improve phylogenetic inference with large phenotypic datasets.
• This method refines our understanding of mammalian evolutionary history and relationships.