A genomic timescale for placental mammal evolution

Area of Science:

• Evolutionary Biology
• Genomics
• Mammalian Phylogenetics

Background:

• The evolutionary timeline and relationships of placental mammals are not fully resolved.
• Previous studies faced limitations due to insufficient genomic data across species.

Purpose of the Study:

• To conduct a comprehensive phylogenetic analysis of placental mammal evolution using extensive genomic data.
• To resolve controversies regarding the timing and pattern of placental mammal speciation.

Main Methods:

• Phylogenetic analysis of 241 placental mammal genome assemblies.
• Comparison of neutral genome-wide phylogenomic signals using concatenation and coalescent methods.
• Analysis of phylogenetic variation across chromosomes and structural variants.

Main Results:

• Interordinal relationships showed low conflict across methods and datasets.
• Conflicts between X-chromosome and autosomal phylogenies were identified in multiple Cenozoic clades.
• Genomic time trees indicated significant cladogenesis before and after the Cretaceous-Paleogene boundary.

Conclusions:

• Cretaceous continental vicariance and the Cretaceous-Paleogene extinction event likely played crucial roles in placental mammal radiation.
• The study provides a robust genomic framework for understanding early placental mammal evolution.