Testing the host specificity hypothesis: delimitation of Gyrodactylus species infecting fishes of the family Profundulidae across their distribution range.

Host specificity, a trait describing how many different hosts a parasite can infect, ranges from strict specialists for parasites associated to a single host species, to generalists for those able to infect several host species, which may even be phylogenetically unrelated. Monogenea are generally considered to be specialist parasites, but this appreciation may be an artifact arising from biased or limited sampling. Here, we evaluate host specificity of species of Gyrodactylus infecting fishes of the family Profundulidae collected in southern Mexico and, crucially, encompassing the whole distribution range of seven profundulid species. We used several molecular species delimitation methods to identify parasite lineages, which consistently recovered six species, four previously known and two new species, which we describe here. Gyrodactylid species infected from one to seven profundulid fish species, spanning the whole range of recognized host specificity associations, from strict specialists to generalists. No clear pattern could be discerned in the host-parasite associations we analysed (phylogenetic, host, geographical), suggesting that the ecological and evolutionary history of Gyrodactylus transcends that of their hosts - and one can envisage that with progressively more in-depth studies, it will be increasingly more difficult to speak of "general" patterns within large and complex groups of parasites, like the genus Gyrodactylus (Monogenea).