Diversity and phylogenetic relationships of entomopathogenic nematodes (Steinernematidae and Heterorhabditidae) from the Sky Islands of southern Arizona

A survey for entomopathogenic nematodes was conducted in oak-juniper woodlands of four mountain ranges (Santa Rita, Santa Catalina, Pinaleño, and Chiricahuas), in southeastern Arizona. From a total of 120 soil samples, 23.3% were EPN-positive. Of them 78.5% were positive for Steinernema spp. and 21.5% were positive for Heterorhabditis spp. An integrated approach, combining both traditional (morphological) and molecular methods, was used for examining the diversity of species of these entomopathogenic nematodes. Two named-species S. oregonense and S. riobrave are reported for the first time in Arizona, expanding their currently known geographic range. In addition to this, three undescribed Steinernema and three Heterorhabditis spp. were recovered. Insular evolution, in part, could account for the geographic distribution of entomopathogenic nematodes in Arizona.