Comparative Systematics of Subterranean Amphipod Crustaceans (Hadzioidea)

The research project presented in this doctoral dissertation is a compilation of six published papers. Therefore, instead of being a single comprehensive project, it is composed of a number of sub-projects. Introductory and summary sections provide structure for the compilation of papers. The research for this dissertation investigates the systematics of genera within the amphipod families Hadziidae Karaman, 1943 and Melitidae Bousfield, 1973. In the family Hadziidae, Bahadzia patilarga is described from an anchialine cave on the southern coast of Cuba, B. caymanensis is described from a weakly brackish-water pool in a small cave on Grand Cayman Island in the Cayman Islands, B. yagerae is thoroughly redescribed, and a phylogenetic analysis of Bahadzia and a number of outgroup genera is performed. Two new genera, Paraholsingerius and Tamaweckelia and two new species, P. mexicanus and T. apalpa are desribed from caves in eastern Coahuila and southern Tamaulipas, Mexico respectively. Holsingerius smaragdinus previously known from a single cave in Val Verde Co., Texas, is elevated to the new genus Paraholsingerius and a second population of P. smaragdinus is recorded from northern Coahuila, Mexico. A new record for Paramexiweckelia from a cave in north-central Coahuila is documented. Four new stygobitic species of Hadzia are described from subterranean waters in the Philippines, Palau and Guam. Liagoceradocus is synonymized with Hadziaand an updated diagnosis for the latter is provided. In the family Melitidae three new species of Tegano are described, two from Panglao Island, Bohol, Philippines and one from Peleliu Island, Palau. Tegano is synonymized with Sriha. A new species of Melita is described that has characters intermediate between those used to define the genera Abludomelita, Melitaand Paraniphargus. Based on this new species and studies by previous authors, it is suggested that Abludomelita may need to be synonymized with Melita. The genus Paraniphargus is synonymized with Melita. Flagitopisa philippensis is redescribed based on collections made from various localities throughout the Philippines. Paratypes of Psammogammarus fluviatilisalso from the Philippines were examined and in both this species and F. philippensis, a new structure was described, which consists of a weakly stalked, subovate coxal-like gill attached to the ventral surface of the first pleonite, just anterior to pleopod 1. Based on this unique character, P. fluviatilis is reassignedFlagitopisa