Background: Founder events have been observed among numerous plants and animal species living on oceanic islands due to the geographic separation of these islands and the small amount of original life they harbor. However, there has been little research on the ecological characteristics of pathogenic microorganisms on islands. Trichophyton rubrum  ranks the most common isolated dermatophyte causing dermatophytosis in clinic and has become an epidemic strain worldwide in recent decades.
Objective: To study the phylogenetic characteristics and the distribution pattern of genetic polymorphism of T. rubrum  in China, which further provide theoretical basis for the prevention and control of T. rubrum .
Methods: In the present study, we sequenced and analyzed the genetic characteristics of 204 T. rubrum  isolates from Hainan Island and other sites in China. Phylogenetic analysis and genetic polymorphisms were studied based on a total of 41,409 high-quality whole-genome SNPs.
Results: The majority of the isolates from Hainan Island clustered together. Mixed T. rubrum  population differentiation was observed among the strains of different geographical origins. In addition, the genetic diversity (π) of the Hainan isolates was low and showed no significant difference from that of isolates from other sites.
Conclusion: This study is the first to discuss general ecological and evolutionary principles related to pathogenic fungi. Our findings reveal a founder effect during the origination of T. rubrum  on Hainan Island and provide guidance regarding prevention and treatment strategies.
Keywords: founder effects, Trichophyton rubrum , genetic diversity, population differentiation