A new species of Leptodiaptomus (Copepoda, Diaptomidae) from Northwestern Mexico with comments on the distribution of the genus

A new species of the freshwater planktonic copepod genusLeptodiaptomus is described for a small pond inNorthwestern Mexico. Leptodiaptomus dodsoni n. sp. canbe easily distinguished mainly by the presence of an unusually largesinusoid spine on male antennular segment 13, and by the features of thefifth legs of both sexes. This genus is known to be distributed mainly inNorth America with 19 recognized species. Of these, six ocur in Mexico, andthe new species seems to be closely related to most of them. It is probablethat this group of species (including the new one) represents thesouthwards radiation of the genus from North America. Compared to theCaribbean and South American, the North American influence seems to be themost relevant for diaptomid copepods in Mexico. At least two Mexicanspecies of Leptodiaptomus, includingL.dodsoni, are restricted in distributional range tohigh-altitude temporal ponds, and both could be considered endemics.