Evolutionary and ecological patterns within the South African Bathyergidae: Implications for taxonomy

Area of Science:

• Zoology and Evolutionary Biology
• Genetics and Phylogeography
• African Mammalogy

Background:

• The family Bathyergidae, comprising six genera of subterranean rodents endemic to sub-Saharan Africa, has limited understood evolutionary history and species richness.
• Existing genetic data suggest the potential presence of multiple cryptic species within the South African genera Georychus, Bathyergus, and Cryptomys.
• Most South African bathyergid species are currently listed as Least Concern by the IUCN Red List.

Purpose of the Study:

• To investigate the genetic and ecological distinctiveness of South African bathyergid genera (Georychus, Bathyergus, Cryptomys).
• To evaluate the taxonomic richness and evolutionary patterns within these genera.
• To explore historical environmental factors influencing their evolutionary trajectories.

Main Methods:

• Utilized four protein-coding genetic markers (one mitochondrial, three nuclear) for comprehensive analysis.
• Employed extensive, distribution-wide sampling schemes with large sample sizes.
• Investigated potential ecological differences among identified intra-generic clades.

Main Results:

• Identified multiple, geographically distinct genetic lineages (clades) within each genus, supported by both mitochondrial and nuclear DNA.
• These lineages show signatures of historical distribution fragmentation driven by major environmental shifts since the Miocene (e.g., uplift, erosion cycles, climate change).
• Distinct ecological differences (geology, vegetation, elevation, rainfall, temperature) were observed between clades, particularly in Georychus and Cryptomys, further delineating lineages.

Conclusions:

• The study supports and expands previous findings suggesting the existence of several cryptic species within the South African Bathyergidae.
• Evolutionary origins appear linked to novel habitats in northeastern South Africa following the Post-African I erosion cycle and significant climate shifts.
• Long-term isolation and ecological divergence have played crucial roles in shaping the distinct lineages observed across these subterranean rodent genera.