Prokaryotic species are sui generis evolutionary units

Area of Science:

• Microbiology
• Evolutionary Biology
• Genetics

Background:

• Prokaryotes lack the gene flow barriers common in eukaryotic species divergence.
• Horizontal gene transfer (HGT) plays a dual role in prokaryotes, promoting genetic cohesion and variation.
• HGT encompasses genetic conversions (homogenization) and introductions (divergence).

Purpose of the Study:

• To explore the impact of HGT on prokaryotic species divergence and cohesion.
• To evaluate the adequacy of conventional species delineation metrics for prokaryotes.
• To propose a new framework for prokaryotic species recognition.

Main Methods:

• Analysis of HGT processes (genetic conversions and introductions).
• Examination of varying HGT levels across prokaryotic species.
• Integration of vertical inheritance with horizontal gene acquisition.

Main Results:

• HGT significantly influences prokaryotic genetic similarity, genomic cohesion, and evolutionary age.
• Conventional species delineation metrics are insufficient for prokaryotes due to HGT.
• Prokaryotic species exhibit unique evolutionary trajectories and population dynamics.

Conclusions:

• A pluralistic approach is essential for prokaryotic species recognition.
• Each prokaryotic species should be considered unique (sui generis).
• Robust taxonomic classifications require integrating vertical inheritance with all HGT sources.