Uncoupled Histories in the Largest Continental Arc of North America: Goodeid Fishes and Their Gyrodactylid Parasites Influenced Differently by the Trans‐Mexican Volcanic Belt

We characterized monopisthocotylans infecting endemic goodeid fishes south of the Trans-Mexican Volcanic Belt (TMVB), a major North American barrier separating the Nearctic and Neotropical biogeographic provinces. Considering that TMVB emergence powerfully influenced goodeid diversification and distribution, we assessed whether it also affected Gyrodactylus lineages associated with these Nearctic hosts. Previously, six Gyrodactylus spp. were known to infect goodeids (Goodea atripinnis, Giradinichthys multiradiatus) within and north of the TMVB; we recorded seven gyrodactylids (three known, four undescribed species) infecting Ilyodon and Allotoca spp. south of the TMVB (S-TMVB). Using phylogenetic (internal transcribed spacer, cytochrome oxidase subunit II) and species delimitation (Assemble Species by Automatic Partitioning and Multispecies Coalescent [MSC] models) analyses, we tested three hypotheses: (1) ancient parasite lineages whose association with goodeids probably predates TMVB emergence occur on both sides of this barrier; (2) following TMVB emergence, some nearctic gyrodactylids will only be found in S-TMVB; (3) gyrodactylids infecting goodeids in S-TMVB switched hosts from other Cyprinodontiformes. Analyses showed that (1) Gyrodactylus tomahuac occurs on both sides of the TMVB; (2) no nearctic parasites were found in S-TMVB, confirming the TMVB is a biogeographical barrier; (3) four undescribed gyrodactylids infecting goodeids S-TMVB are morphologically and phylogenetically closely related to parasites infecting profundulid fishes, suggesting host switches from these neotropical hosts whose northern distribution limit is the TMVB. Our data reveal a complex and profound evolutionary history of Gyrodactylus species parasitizing goodeids, uncoupled from that of their hosts. Phylogenetic analyses and MSC models suggest three main parasite groups are associated with goodeid fishes and that gyrodactylids have historically switched hosts between Cyprinodontiformes (Goodeidae, Profundulidae, and Poeciliidae).