RESUMEN
Mangrove killifishes of the genus Kryptolebias have been historically classified as rare because of their small size and cryptic nature. Major gaps in distribution knowledge across mangrove areas, particularly in South America, challenge the understanding of the taxonomic status, biogeographical patterns and genetic structuring of the lineages composing the self-fertilizing "Kryptolebias marmoratus species complex." In this study, the authors combined a literature survey, fieldwork and molecular data to fill major gaps of information about the distribution of mangrove killifishes across western Atlantic mangroves. They found that selfing mangrove killifishes are ubiquitously distributed across the Caribbean, Central and South American mangroves and report 14 new locations in South America, extending the range of both the "Central clade" and "Southern clade" lineages which overlap in the Amazon. Although substantial genetic differences were found between clades, the authors also found further genetic structuring within clades, with populations in Central America, north and northeast Brazil generally showing higher levels of genetic diversity compared to the clonal ones in southeast Brazil. The authors discuss the taxonomic status and update the geographical distribution of the Central and Southern clades, as well as potential dispersal routes and biogeographical barriers influencing the distribution of the selfing mangrove killifishes in the western Atlantic mangroves.