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Phenotypic and Genetic Diversity of Arctic Charr (Salvelinus Alpinus) in the Lake District, UK

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Phenotypic and Genetic Diversity of Arctic Charr (Salvelinus Alpinus) in the Lake District, UK Durham E-Theses Phenotypic and genetic diversity of Arctic charr (Salvelinus alpinus) in the Lake District, UK Corrigan, Laura How to cite: Corrigan, Laura (2008) Phenotypic and genetic diversity of Arctic charr (Salvelinus alpinus) in the Lake District, UK, Durham theses, Durham University. Available at Durham E-Theses Online: http://etheses.dur.ac.uk/1337/ Use policy The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that: • a full bibliographic reference is made to the original source • a link is made to the metadata record in Durham E-Theses • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders. Please consult the full Durham E-Theses policy for further details. Academic Support Oce, Durham University, University Oce, Old Elvet, Durham DH1 3HP e-mail: [email protected] Tel: +44 0191 334 6107 http://etheses.dur.ac.uk 2 Phenotypic and genetic diversity of Arctic charr (Salvelinus alpinus) in the Lake District, UK By The copyright of this thesis rests with the Laura Corrigan author or the university to which it was submitted. No quotation from it, or information derived from it may be published without the prior written consent of the author or university, and any information derived from it should be acknowledged. School of Biological and Biomedical Sciences Durham University 2008 03 MAR2009 Submitted for the degree of Doctor of Philosophy ýý ýý-, ýrY Abstract The generalaim of this thesis was to assessthe phenotypic and genetic diversity of Arctic charr (Salvelinus alpinus) populations in the Lake District, UK, in order to understandthe key evolutionary mechanismsinvolved in the developmentof resourcepolymorphisms and their genetic divergence. Arctic charr exhibit high phenotypic variability throughout their range. This study assessedthe phenotypic variation between three main lakes, Wastwater, Windermere and Coniston Water, as well as within Coniston Water and Windermere, using principal component analysis of morphological traits. The phenotype varied between these three lakes, and evidence of sympatric polymorphisms has been shown in Coniston Water where two morphs occur. These morphs were similar to those that have been repeatedly described in the literature to be a `pelagic' zooplanktivorous morph and a `benthic' morph. The dietary analysis, using both stomach contents analysis and stable isotope analysis, found the dietary segregation between the morphs in Coniston Water to be to a lesser extent than described elsewhere, but did however, suggest a generalist vs. specialist situation. Despite the presence of multiple breeding populations in Windermere, the charr are relatively monomorphic with much of the morphological variation being explained by differences between the sexes. However, their morphology, consistent with a zooplanktivorous diet as was described previously, is not in concordance with their present diet, which had a higher proportion of benthic prey. This indicates that at present the association between diet and morphology is not as close in the Windermere population than has been seen in other lakes. The assessmentof ten microsatellite DNA loci allowed the genetic structure of Arctic charr populations within the Lake District to be resolved. All lakes showed significant differentiation. Relatively weak but significant differentiation was also found betweenthe four putative spawning populations in Windermere. Low levels of gene flow betweenthese populations were also found suggestingthat although thesepopulations exhibit philopatry, some individuals stray from their natal grounds during spawning. For Coniston Water, the microsatellite DNA analysiswas less conclusive, with the FCA indicating some divergencebetween the two morphotypes that was not detectedin the F-statistics. Reproductive isolation is therefore incomplete, with high geneflow betweenthe morphs, although sample sizeswere unfortunately too small in order to test migration rates. Mitochondrial DNA analysis indicated that all Lake District populations diverged from an ancestralpopulation common to all lakes. The timing of their divergenceis consistentwith the retreat of the ice and formation of the lakes after the last glacial maximum. ii Declaration The material containedwithin this thesis has not previously been submitted for a degreeat Durham University or any other university. The researchreported here has been conductedby the author unless statedotherwise. © The copyright of this thesis restswith the author. No quotation from it should be published without their prior written consentand information derived from it should be acknowledged. iii Acknowledgements Thanks to my supervisorshere at Durham, Rus Hoelzel and Martyn Lucas, for all there help and support throughout my PhD. And also thanks to my supervisorfrom CEH Lancaster,Ian Winfield, who patiently answeredmany many emails. This study would not have been possible without the help of many people, in sample collection especially. Thanks to Janice Fletcher and Ben James, CEH Lancaster, who collected hundreds of samples and taught me the ropes out on the boat. Thanks to the Freshwater Biological Association, for the loan of their boat, Velia, for our sampling trip in 2005. Also thanks to Roger Sweeting and Anne Powell who kindly put us up during this trip. Thanks to Scottish Natural Heritage and the Windermere Angling Association for further samples. Thanks to Colin MacPherson, Durham University, and Chris Harrod, Queen's University, Belfast, for stable isotope analysis. I am very appreciativeof Colin Adams, University of Glasgow, Jon Grey, Queen Mary University and Chris Harrod, Queen's University, for giving their valuable time and advice, which was incredibly useful in the interpretation of my results. I would also like to thank all membersof the Molecular Ecology Group, both past and present,who have all offered endlessadvice and support in one way or another that has kept me sane,especially in the last nine months. I would especially like to mention Karis Baker, Ross Barnett, Mark deBruyn, Vittoria Elliott, Andy Foote, Georgios Gkafas, Carlos De Luna Lopez, Andre Moura, Malgorzata Pilot, Iris Segura,Joanne Stamford, and Tom White for all their wonderful advice and great friendship. I am also grateful to the Natural Environment ResearchCouncil for funding this project. Finally, I would like to thank my family and friends and especially my parentsfor their financial and emotional support over the years. iv Contents Page Abstract ......................................................................................................................i Declaration ............................................................................................................... iii Acknowledgements .................................................................................................. iv Contents Page ........................................................................................................... Vi Chapter 1: General Introduction ............................................................................... 1 Thesis Aims ............................................................................................................. 13 Chapter 2: Long-term changes in feeding ecology of Arctic charr (Salvelinus alpinus) in Windermere in response to environmental changes 15 2.1. Introduction ........................... .....................................................................................................15 2.1.1. The population dynamics Arctic in Windermere 15 of charr ........................ 2.1.2. Feeding Arctic 17 ecology of charr ............................................................... 2.1.2.1. The use of stable isotopesin dietary studies 18 2.1.3. Chapter ..................................... aims............................................................................................. 20 2.2. Methods ...........................................................................................................21 2.2.1. Study site ..................................................................................................21 2.2.2. Sample collection .....................................................................................22 2.2.3. Dietary analysis........................................................................................ 25 2.2.4. Stable isotope analysis .............................................................................26 2.3. Results .............................................................................................................27 2.3.1. Dietary analysis........................................................................................ 27 2.3.2. Stable isotope analysis .............................................................................32 2.4. Discussion .......................................................................................................34 Chapter 3: Phenotypic diversity of Arctic charr in populations in the Lake District, UK ................................................................................................................ 42 3.1. Introduction .....................................................................................................42 3.1.1. Phenotypic in Arctic 42 variation
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