Diptera) in Disjunct Grasslands of the Soüthern Yukon
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DIVERSITY AND ZOOGEOGRAPHY OF BRACHYCERA (DIPTERA) IN DISJUNCT GRASSLANDS OF THE SOüTHERN YUKON Stéphanie Boucher Department of Natural Resource Sciences McGill University, Montreal November 1998 A thesis submitted to the Faculty of Graduate Studies and Research in partial fiilfillment of the requirements of the degree of Master of Science O Stéphanie Boucher, 1998 National Library Bibliothèque nationale 1*1 of Canada du Canada Acquisitions and Acquisitions et Bibliographie Services services bibliographiques 395 Wellington Street 395. rucr WNmgtori OnawaON KlAONQ O(tawa0N K1AW Canada canada The author has granted a non- L'auteur a accordé une Licence non exclusive licence aliowing the exclusive permettant à la National Library of Canada to Bibliothèque nationale du Canada de reproduce, loan, distribute or sell reproduire, prêter, distribuer ou copies of this thesis in microform, vendre des copies de cette thèse sous paper or electronic formats. la forme de microfiche/film, de reproduction sur papier ou sur format électronique. The author retains ownership of the L'auteur conserve la propriété du copyright in this thesis. Neither the droit d'auteur qui protège cette thèse. thesis nor substantial extracts kom it Ni la thèse ni des extraits substantiels may be printed or otherwise de celle-ci ne doivent être imprimés reproduced without the author's ou autrement reproduits sans son permission. autorisation. Frontispiece. South-facing dope near Carcross, Yukon 3.4.1. Widespread Species ......................................... 74 3.4.2. Western Species ............................................ 74 3.4.3. Disjunct Species ............................................ 74 3.4.4. Beringian Species .......................................... 75 4.Discussion ................................................................ 76 4.1. Abundance of Grassland Brachycera .................................... 76 4.1.1. Dominant Taxa ............................................ 76 4.1 .2 . Dominant Guilds ........................................... 77 4.2. Diversity of Grassland Brachycera ..................................... 78 4.2.1. Taxonomic Diversity ........................................ 78 4.2.2. Diversity of Guilds ......................................... 81 4.3. Zoogeographic Patterns .............................................. 81 4.3.1. Widespread Species ......................................... 82 4.3.2. Western Species ............................................ 83 4.3.3. Disjunct Species ............................................ 84 4.3 .4 . Beringian Species .......................................... 86 4.4. Geographic Affinities and Origins of the Brachycera Fauna ................. 86 4.4. 1 . Widespread Species ......................................... 87 4.4.2. Western Species ............................................ 88 4.4.3. Disjunct Species ............................................ 89 4.4.4. Beringian Species .......................................... 91 4.5. Insects and the Origin of Southern Yukon Grasslands ...................... 92 4.6. Recommendations for Future Research .................................. 93 5.References ................................................................ 95 LIST OF TABLES 1 . Diversity and abundance of vegetation identified on primary study sites ............... 107 2 . List of Brachycera families identified to species level. with collaborating specialists who provided or confirmed species identifications and taxonomie keys used .......... 108 3 . Brachycera species. with overall abundance. ecologicd guild and distribution pattern .... 109 LIST OF FiCURES 1 . Map of the Yukon showing known occurrence of xeric grassland cornrnunities ......... 116 2a . Map of the Yukon showing unglaciated regions ................................ 117 2b . Map of the Yukon showing some of the main mountain ranges ..................... 117 3 . Map of the Yukon showing location of study sites ................................ 118 4 . Map of North Arnerica showing division of western and eastern regions .............. 119 5 . Distribution of Lusiopogon canus ............................................. 120 6 . Distribution of Oqna atterima ............................................... 120 7 . Distribution of Rhagoletis juniperina .......................................... 121 8. Distribution of Tephriris leaviremis ........................................... 121 9 . Distribution of Trixoscelisfirmipennis ......................................... 122 10 . Brachycera abundance; dominant families. A . 1997; B . 1998; C . Both years combined . 123 1 1. Brachycera abundance; dominant species. A . 1997; B . 1998; C. Both years combined ... 124 12 . Brachycera abundance; dominant guilds. A . 1997; B . 1998; C . Both years combined ... 125 13. Brachycera diversity; five most dominant families. A . 1997; B . 1998; C . Both years combined ............................................................ 126 14. Brachycera diversity; dominant guilds. A . 1997; B. 1998; C . 90th years combined ..... 127 15 . Geographic patterns of Brachycera ........................................... 128 ABSTRACT The diversity and zoogeography of Diptera (Brachycera) of disjunct xeric grasslands in the southern Yukon were studied. Over 20,000 flies were collected representing 32 families and 2 13 species. In terms of abundance, the predacious guild dominated (54% of total specimens) due mostly to the farnily Chamaemyiidae which represented 45% of al1 specimens. In terms of diversity, the phytophagous and parasitoid guilds were dominant (25.5% of total species each). The most diverse families were Agromyzidae (32 vies), Chloropidae (3 1 species), Tachinidae (23 species) and Pipunculidae (20 species). Thirty-four undescribed species were collected and 58 species were recorded for the first time in the Yukon. Zoogeographic analysis indicates that the Diptera fauna of these grasslands is dominated by widespread Nearctic or Holarctic species, but the fauna also inchdes southern grassland species with disjunct distributions, and species endemic to Beringia. The presence of endemic and disjunct species suggests that these grassiands were present in Benngia during the Wisconsinan and acted as a refugium for grassland Diptera. RÉSUMÉ On trouvera ici une étude sur la diversité et la zoogéographie des diptères (Brachycera) associés avec les prairies reliques du sud du Yukon. Plus de 20 000 spécimens de brachycères ont été collectés comprenant 32 familles et 213 espèces. En terme d'abondance, les prédateurs dominaient (54% de tous les spécimens), dû essentiellement a la famille Chamaemyiidae (45% de tous les spécimens). Au niveau de la diversité, les phytophages et les parasites dominaient, représentant chacun 25.5% de toutes les espèces. Les familles les plus diversifiées étaient les Agromyzidae (32 espèces), Chioropidae (3 1 espèces), Tachinidae (23 espèces) et Pipuncuiidae (20 espéces). Trente-quatre espèces non décrites ont été collectées et 58 espèces ont été pour la première fois recensées au Yukon. L'analyse zoogéographique indique que la faune diptérienne de ces prairies est dominée par des espèces répandues dans la zone néarctique ou bien holarctique. De plus, certaines espèce ont une distribution discontinue avec celles des prairies du sud, et d'autres sont endémiques a la Béringie. La présence des ces espéce suggère que les prairies reliques du Yukon étaient présentes en Bénngie pendant le Wisconsinien et qu'elles ont offert un refuge aux diptères adaptées aux prairies. vii ACKNOWLEDGEMENTS 1 am extremely gratefûl to my supervisor, Dr. Terry A. Wheeler, for his assistance throughout this project. 1 would like to thank hirn particularly for always king available for the past two years, and for his constructive comments and advice with this thesis. I also really appreciated his assistance collecting in the Yukon, he was a valued field partner, and his amazing knowledge about insects and so many other things made our daily conversation really enriching. I am also very grateful to him for taking students to conferences, and making sure that we are exposed to the scientific world. Dr. Wheeler's contagious enthusiasm and passion for insects have always been a source of motivation for me, and he is the one who encourageci me to do a Master's in entomology. 1 thank hirn for believing in me and giving me the chance to do this Master's with him. 1 am also thankfûl to my cornmittee members, Dr. D. J. Lewis for reviewing this manuscript and providing thoughtfid comments, and Dr. J. M. Curnming for giving me access to the Canadian National Collection in Ottawa, for providing identifications of the Empididae and for his hospitality and encouragement. Other scientists who provided identifications are R. A. Cannings (Royal British Columbia Museum), S. D. Gaimari (University of Illinois), S. A. Marshall (University of Guelph), A. L. Norrbom (Smithsonian Institution), J. R. Vockeroth (Agriculture and Agi-Food Canada), T. A- Wheeler (McGill University) and D. M. Wood (Agriculture and Agi-Food Canada). To these individuals 1 express my greatest appreciation. 1 also thank Doug Kritsch (Agriculture and A-gi- Food Canada) who helped with critical point cirying of my flies and al1 the entomologists at the Canadian National Collection for discussions and advice. 1 would also like to acknowledge the Heritage Branch, Yukon Territorial Governrnent for providing a Scientists and Explorers License to collect in the Yukon. The following organizations