African origin and Late Cretaceous divergence of the Middle American catfish Lacantunia enigmatica corroborated by a global mitogenome phylogeny

Abstract

Two decades ago, the new siluriform family Lacantuniidae was erected to accommodate its sole known extant representative, Lacantunia enigmatica, a morphologically aberrant catfish restricted to the Middle Usumacinta River basin along the Guatemala-Mexico border. While its discovery was unexpected, its proposed phylogenetic placement--nested within a large clade of exclusively African-endemic families rather than closely related to regionally sympatric North American or Neotropical lineages--was baffling. To test this counterintuitive phylogenetic and biogeographic hypothesis, we collected new specimens of L. enigmatica and sequenced, assembled, and annotated for the first time its complete mitochondrial genome. We then constructed the most taxonomically comprehensive mitochondrial data matrix of catfishes to date by including published mitochondrial genomes representing the majority of siluriform families. Using Bayesian co-estimation of phylogeny and divergence times, we inferred the evolutionary position of the puzzling L. enigmatica within a time-scaled global catfish phylogeny. Our results offer improved resolution and understanding of higher-level siluriform relationships and refine the timescale of catfish evolution. Crucially, our findings corroborate the hypothesis that L. enigmatica is sister to the African family Claroteidae and represents a relict lineage that originated in Africa during the Late Cretaceous (74.99 Ma; 95% HPD=68.58-81.39) and eventually culminated in Middle America. Our results therefore uphold the necessity of transoceanic dispersal--as opposed to Gondwanan vicariance--to explain this otherwise puzzling biogeographic pattern.