Systematics of the Subterranean Amphipod Genus Stygobromus (Crangonyctidae), Part II: Species of the Eastern United States JOHN R. HOLSINGER SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY · NUMBER 266 SERIES PUBLICATIONS OF THE SMITHSONIAN INSTITUTION Emphasis upon publication as a means of "diffusing knowledge" was expressed by the first Secretary of the Smithsonian. In his formal plan for the Institution, Joseph Henry outlined a program that included the following statement: "It is proposed to publish a series of reports, giving an account of the new discoveries in science, and of the changes made from year to year in all branches of knowledge." This theme of basic research has been adhered to through the years by thousands of titles issued in series publications under the Smithsonian imprint, commencing with Smithsonian Contributions to Knowledge in 1848 and continuing with the following active series: Smithsonian Contributions to Anthropology Smithsonian Contributions to Astrophysics Smithsonian Contributions to Botany Smithsonian Contributions to the Earth Sciences Smithsonian Contributions to the Marine Sciences Smithsonian Contributions to Pa/eob/o/ogy Smithsonian Contributions to Zoology Smithsonian Studies in Air and Space Smithsonian Studies in History and Technology In these series, the Institution publishes small papers and full-scale monographs that report the research and collections of its various museums and bureaux or of professional colleagues in the world cf science and scholarship. The publications are distributed by mailing lists to libraries, universities, and similar institutions throughout the world. Papers or monographs submitted for series publication are received by the Smithsonian Institution Press, subject to its own review for format and style, only through departments of the various Smithsonian museums or bureaux, where the manuscripts are given substantive review. Press requirements for manuscript and art preparation are outlined on the inside back cover. S. Dillon Ripley Secretary Smithsonian Institution SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY · NUMBER 266 Systematics of the Subterranean Amphipod Genus Stygobromus (Crangonyctidae), Part II: Species of the Eastern United States John R. Holsinger SMITHSONIAN INSTITUTION PRESS City of Washington 1978 ABSTRACT Holsinger, John R. Systematics of the Subterranean Amphipod Genus Stygo- bromus (Crangonyctidae), Part II: Species of the Eastern United States. Smith- sonian Contributions to Zoology, number 266, 144 pages, 77 figures, 1978.—The amphipod genus Stygobromus is widespread in the subterranean waters of the United States and is recorded from a variety of groundwater habitats. A revised diagnosis of the genus is given and a tentative division into three subgeneric groups is proposed. The recently proposed synonymy of Stygonectes and Apocran- gonyx with Stygobromus is reaffirmed. Forty-eight described species are herein recognized from the Appalachian and Coastal Plain regions of the eastern United States, of which 30 are newly described, three are completely redescribed, and new systematic data are given for the remainder. In addition, six populations are provisionally recognized as distinct species but are not described because of lack of adequate material. On the basis of morphology and geographic distribution, 12 species groups are recognized in the eastern United States, eight of these being newly established herein. Ancestral stygobromids are now believed to have occurred earlier in the fresh- water environment than originally suggested. Species of Stygobromus occupy a diversity of groundwater and groundwater-related habitats in the eastern United States, including primarily cave pools and streams, phreatic reservoirs and the hypotelminorheic media of seeps and small springs. Habitat selection is based on niche breadth and movement through shallow groundwater, both of which are believed to be significant factors in dispersal and geographic distribution. A number of species occur syntopically and/or sympatrically but most closely allied species have allopatric ranges. The possibility that several species are glacial relicts of the Pleistocene is raised. OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded in the Institution's annual report, Smithsonian Year. SERIES COVER DESIGN: The coral Montastrea cavernosa (Linnaeus). Library of Congress Cataloging in Publication Data Holsinger, John R. Systematics of the subterranean amphipod genus Stygobromus (Gammaridae). (Smithsonian contributions to zoology, no. 160, 266) Vol. 2 has title: Systematics of the Subterranean amphipod genus Stygobromus (Crangonyctidae) Bibliography: v. 1, p. 62-63; v. 2, p. Contents: pt. 1. Species of the Western United States.—pt. 2. Species of the Eastern United States. Supt. of Docs, no.: SI 1.27:266 1. Stygobromus—Classification. 2. Crustacea—Classification. I. Title. II. Series: Smithsonian Institution. Smithsonian contributions to zoology, no. 160, 266 [etc.] QL1.S54 no. 160, etc. 59l'.O8s [595'.37l] 73-9808 [QL444M315] Contents Page Introduction 1 Methods and Materials 2 Acknowledgments 2 Stygobromus Cope 3 Key to Species Groups and Ungrouped Species of Stygobromus of the Eastern United States 4 The emarginatus Group 6 Key to the Species of the emarginatus Group 6 Stygobromus emarginatus (Hubricht) 7 Stygobromus morrisoni (Holsinger) 8 Stygobromus mundus (Holsinger) 10 Stygobromus hoffmani, new species 10 Stygobromus fergusoni, new species 14 Stygobromus franzi, new species 17 Stygobromus cooperi (Holsinger) 20 Stygobromus obrutus, new species 20 Stygobromus culveri, new species 23 The ackerlyi Group 26 Key to the Species of the ackerlyi Group 26 Stygobromus ackerlyi, new species 26 Stygobromus ine×pectatus, new species 29 The gracilipes Group 31 Key to the Species of the gracilipes Group 31 Stygobromus gracilipes (Holsinger) 31 Stygobromus conradi (Holsinger) 32 The spinosus Group 32 Key to the Species of the spinosus Group 32 Stygobromus spinosus (Hubricht and Mackin) 33 Stygobromus pseudospinosus, new species 36 Stygobromus kenki, new species 39 The ephemerus Group 42 Key to the Species of the ephemerus Group 42 Stygobromus ephemerus (Holsinger) 43 Stygobromus estesi, new species 43 Stygobromus parvus (Holsinger) 46 Stygobromus pollostus, new species 46 Stygobromus nanus, new species 51 Stygobromus redactus, new species 51 The spinatus Group 54 Stygobromus spinatus (Holsinger) 54 The mackini Group 60 Key to the Species of the mackini Group 60 iii SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY Page The mackini Subgroup 61 Stygobromus mackini Hubricht 61 Stygobromus abditus, new species 67 Stygobromus dicksoni, new species 70 Stygobromus finleyi, new species 74 The leensis Subgroup 76 Stygobromus leensis, new species 76 The sparsus Subgroup 79 Stygobromus sparsus, new species 79 Stygobromus barryi, new species 83 Stygobromus carolinensis, new species 85 The grandis Subgroup 88 Stygobromus grandis, new species 88 The cumberlandus Group 91 Key to the Species of the cumberlandus Group 92 Stygobromus cumberlandus, new species 92 Stygobromus interitus, new species 95 The phreaticus Group 98 Stygobromus phreaticus, new species 98 The araeus Group 101 Stygobromus araeus (Holsinger) 102 The pizzinii Group 102 Stygobromus pizzinii (Shoemaker) 102 Stygobromus indentatus (Holsinger) 103 The tenuis Group 103 Stygobromus tenuis tenuis (Smith) 103 Stygobromus tenuis potomacus (Holsinger) 104 Stygobromus allegheniensis (Holsinger) 105 Stygobromus hayi (Hubricht and Mackin) 106 Species Unassigned to Groups 106 Stygobromus stellmacki (Holsinger) 106 Stygobromus baroodyi, new species 107 Stygobromus borealis, new species 110 Stygobromus biggersi, new species 113 Stygobromus stegerorum, new species 117 Stygobromus fecundus, new species 120 Stygobromus minutus, new species 123 Stygobromus species 125 Zoogeographical and Ecological Considerations 126 Origin of Freshwater Stygobromids 126 Habitat Diversity 127 Geographic Distribution and Dispersal 130 Co-occurrence of Species 138 Glacial Relicts 140 Literature Cited 142 Systematics of the Subterranean Amphipod Genus Stygobromus (Crangonyctidae), Part II: Species of the Eastern United States John R. Holsinger Introduction Part I of a series of three papers planned to revise the systematics of Stygobromus treated 18 Prior to recent papers by Karaman (1974) and species (17 newly described) from the western Holsinger (1977), which suggested lumping Stygo- United States (Holsinger, 1974). The present paper, bromus, Stygonectes, and Apocrangonyx, 28 species which is Part II of the series, treats 48 species: 30 had been assigned to the genus Stygobromus (Hol- are newly described, three previously described singer, 1974), 29 to the genus Stygonectes (Holsinger, species are completely redescribed, and new data 1967), and six to the genus Apocrangonyx (Hol- are given for the remaining 15. Of the 18 previously singer, 1969b). In the present paper, 30 new species described species treated, 13 were originally assigned are described and the synonymy of Stygonectes and to Stygonectes (Holsinger, 1967, 1972), three to Apocrangonyx with Stygobromus is reaffirmed. The Apocrangonyx (Holsinger, 1969b, 1972), and two to results of the present study bring the total number Stygobromus (Holsinger, 1972). Part III, now in the of species in Stygobromus to 93, making it one of early stages of preparation, will cover 26 previously the largest genera of freshwater amphipod crus- described species and approximately 30 new (pro- taceans. visionally