Alien Species and Propagules in the Antarctic: Movements Through Space and Time
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Alien species and propagules in the Antarctic: movements through space and time by Jennifer Elizabeth Lee Submitted in partial fulfilment for the degree Doctor of Philosophy in Zoology at Stellenbosch University Department of Botany and Zoology Faculty of Science Supervisor: Prof. Steven L. Chown Date: October 2008 i Declaration By submitting this thesis electronically, I declare that the entirety of the work contained therein is my own, original work, that I am the owner of the copyright thereof (unless to the extent explicitly otherwise stated) and that I have not previously in its entirety or in part submitted it for obtaining any qualification. Jennifer E. Lee Date: 4 February 2009 Copyright © 2008 Stellenbosch University All rights reserved i Acknowledgments I thank Steven Chown whose boundless enthusiasm for science and passion for the Antarctic were an inspiration to me throughout this PhD. This body of work has benefited immeasurably because of his input and guidance. Thanks to my family who have encouraged me at every step of the way. I have spent a long time away in distant places but I felt they were with me always. Being apart, but knowing we will always be together has given me strength and I am humbled by the selfless support they have given me. I specifically want to acknowledge my grandmother, Dora Smith, for instilling in me a positive and pragmatic outlook on life. She planted a seed and I hope she would be proud of what it has grown in to. Andrew Collier has shared my highs and always been there to lift me out of my lows. He has provided great distraction and invaluable focus. A special mention goes to Brian Newham. The many cups of tea and crazy nights out under the stars, have kept life in perspective and his passion and tenderness for the great white wilderness we both love has, and continues to be, an inspiration. Heartfelt thanks to those people who have helped me in the field, whether it was early mornings at the dockside, long wet days on Marion, or cold nights in a tent in Antarctica, I could not have done this work without you and I will be forever grateful. I am particularly indebted to Erika Nortjé, Elrike Marais, Charlene Janion and Saskia Goldberg for assistance in collection of much of the physiological data used in Chapter 7 and to Bettine Jansen van Vuuren for the genetic analyses in Chapters 6 and 7. Members of the Aliens in Antarctica project have provided insightful debate and discussion. Thanks also to the many people who have patiently given up their time to read this thesis and give valuable comment. This is particularly directed at my office mates, Justine Shaw and Peter Le Roux, whose input has improved the quality of this work significantly. ii The Centre for Invasion Biology and Department of Botany and Zoology, Stellenbosch University, are thanked for financial support. The South African National Antarctic Programme provided excellent logistic support throughout this project. I would also like to acknowledge Smit Marine, and particularly Jon Klopper for the invaluable technical information he provided on the SA Agulhas. Marine Solutions Ltd. gave outstanding technical support for the ROV. Finally, thanks to my many friends and colleagues at the C.I.B, you guys have enriched my time in South Africa and I have many happy memories which will be with me forever. iii Abstract Although the impacts of biological invasions are widely appreciated, a bias exists in research effort to post‐dispersal processes because of the difficulties of measuring propagule pressure and the detecting of newly established species. Here the Antarctic is used as a model system in which to quantify the initial dispersal of alien species and investigate the factors that contribute to the establishment and range dynamics of alien species once they have arrived in the region. Human movements are known to transport alien species into the Antarctic, some of which have successfully established and had wide ranging consequences in recipient ecosystems. Considering terrestrial flora, this research found that over 700 seeds from 99 taxa, including some species known to be invasive, are transported into the Antarctic each year in association with South African National Antarctic Programme (SANAP) passenger luggage and cargo. The first ever assessment of propagule drop‐off indicated that 30‐50% of these propagules will enter the recipient environment. Further results suggested that the construction of the British Antarctic Survey Halley VI station will facilitate the transport of over 5000 seeds from 34 taxa into the region, making this a significant pathway for introductions. Propagule pressure due to SANAP logistics is also considerable for marine species. Fouling assemblages on the external hull surfaces of the SANAP resupply vessel, the SA Agulhas, form only once the vessel’s anti‐fouling paint has been damaged by travel through sea ice and are characterised by low diversity. Ice scour prevents fouling assemblages from being transported to the Antarctic continent, but assemblages remain largely intact when travelling to sub‐Antarctic Islands. In the sea‐chests of the vessel populations of a known invasive, Mytilus galloprovincialis, were found with some individuals having survived transportation to the Antarctic region on multiple occasions. Once species have overcome initial dispersal barriers, they face further ecological and physiological challenges in order to establish in the recipient region. The parasitoid wasp Aphidius matricariae was first recorded on Marion Island in 2001. Surveys around the island iv show that adult abundance and the frequency of aphid parasitism are highest adjacent to a common anchor point of the SA Agulhas and decline away from this region. Genetic diversity was low, suggesting that the population was established from a single introduction. This highlights that high propagule pressure is not necessary for successful establishment of introduced invertebrates. Another species that has overcome the dispersal barrier is the terrestrial slug Deroceras panormitanum, which was introduced to Marion Island in the 1970’s and has since spread throughout much of the coastal habitat of the island. For this species range limits are set by intolerance of low temperature and salinity, and abundance structure is characterized by patches and gaps which are associated with this species inability to tolerate dry conditions. To prevent further alien introductions in the region, targeted management of high risk pathways is required. In addition, increased vigilance is needed to detect and manage newly established aliens before their ranges expand. v Opsomming Alhoewel die impak van biologiese indringings in die breë waardeer word, bestaan daar vooroordeel in navorsingspogings ten opsigte van na‐verspreidingsprosesse, weens die moeilikhede om verspreidingseenheid druk te meet en in die opsporing van nuut gevestigde spesies. Hier word die Antarktiese streek as ‘n model sisteem gebruik waarin die aanvanklike verspreiding van uitheemse spesies gekwantifiseer kan word en om die faktore wat bydrae tot die vestiging en grens dinamika van uitheemse spesies te ondersoek, wanneer hulle in ’n streek aangekom het. Menslike bewegings is bekend daarvoor om uitheemse spesies na die Antarktiek te vervoer, sommige waarvan suksesvol gevestig het en omvattende gevolge in die ontvanger ekosisteme gehad het. Aangaande terrestriële flora het hierdie navorsing gevind dat oor die 700 sade van 99 taxa, insluitende sommige spesies wat bekend is om indringend te wees, jaarliks na die Antarktiek vervoer word in assosiasie met die Suid Afrikaanse Nasionale Antarktiese Program (SANAP) se bagasie en vrag. Die eerste waardebepaling van verspreidingseenheid afgooi het aangedui dat 30‐50% van hierdie verspreidingseenhede die ontvanger omgewing sal binnedring. Verdere resultate het voorgestel dat die konstruksie van die Britse Antarktiese Opname Halley VI stasie die vervoer van 5000 sade van 34 taxa sal fasiliteer die streek in, wat dit ’n betekenisvolle weg maak vir indringings. Verspreidingseenheid druk is ook, as gevolg van die SANAP logistiek, aanmerklik vir mariene spesies. Vuilgoed versamelings op die eksterne omhullende oppervlaktes van die SANAP her‐voorsieningsvaartuig, die SA Agulhas, vorm wanneer die vaartuig se anti‐vuilgoed verf beskadig is met reis deur see‐ys en word gekenmerk deur lae diversiteit. Ys skuring voorkom dat vuilgoed versamelings vervoer word na die Antarktiese kontinent, maar versamelings bly grootliks vasgeheg wanneer na sub‐Antarktiese eilande gereis word. Populasies van ’n welbekende indringer, Mytilus galloprovincialis, is gevind in die see‐storingsarea van die vaartuig, met sommige individue wat die vervoering na die Antarktiese streek oorleef het op verskeie geleenthede. vi Wanneer spesies die aanvanklike verspreidingshindernisse oorkom het, staar hulle verdere ekologies en fisiologiese uitdagings in die gesig ten einde in die ontvanger streek te vestig. Die parasitiese wespe Aphidius matricariae is vir die eerste keer op Marion aangeteken in 2001. Opnames om die eiland toon dat volwasse oorvloed en die frekwensie van plantluis parasitisme die hoogste is aangrensend die algemene ankerpunt van die SA Agulhas en afneem weg van die omgewing af. Genetiese diversiteit was laag, wat voorstel dat die populasie gevestig het van ’n enkele bekendstelling. Dit lig uit dat hoë verspreidingseenheid druk nie nodig is vir die suksesvolle vestiging van bekendgestelde invertebrata nie. ‘n Ander spesie wat die verspreidingshindernisse