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Morphological Variation in Red-Backed Voles (Myodes Gapperi) in Québec and Western Labrador

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Morphological Variation in Red-Backed Voles (Myodes Gapperi) in Québec and Western Labrador Morphological variation in red-backed voles (Myodes gapperi) in Québec and western Labrador Rodrigo Barata Souto Lima Department of Biology McGill University, Montreal A thesis submitted to McGill University in partial fulfillment of the requirements of the degree of Master of Science Submitted August 2012 © Rodrigo Lima 2012 2 Table of contents Abstract .......................................................................................................... 4 Résumé ........................................................................................................... 5 Contribution of the authors ............................................................................. 6 Acknowledgements ......................................................................................... 7 List of tables .................................................................................................... 9 List of figures ................................................................................................. 10 General introduction ..................................................................................... 12 Literature review ........................................................................................... 13 1 - Ecotypic variation ............................................................................................ 13 2 - Environmental conditions in Québec ................................................................ 19 2.1 - Climate .............................................................................................................. 19 2.2 - Ecozones ........................................................................................................... 20 2.3 - Primary productivity ......................................................................................... 22 3 - Southern red-backed vole, Myodes gapperi (Vigors, 1830) ................................ 22 3.1 - Origin and evolution ......................................................................................... 22 3.2 - Distribution and preferred habitats .................................................................. 24 3.3 - Diet .................................................................................................................... 25 3.4 - Home range ....................................................................................................... 27 3.5 - Activity pattern ................................................................................................. 27 3.6 - Physiology ......................................................................................................... 28 4 - Morphometrics ................................................................................................ 30 4.1 - A brief history of morphometrics ..................................................................... 30 4.2 - Applications of morphometrics ........................................................................ 31 3 4.3 - Multivariate or “traditional” morphometrics ................................................... 32 4.4 - Outline analysis ................................................................................................. 36 4.5 - Landmark geometric morphometrics ............................................................... 38 4.6 - General methods used in this study ................................................................. 42 References .................................................................................................... 44 Morphological variation in red-backed voles (Myodes gapperi) in Québec and western Labrador .......................................................................................... 59 ABSTRACT ............................................................................................................ 60 INTRODUCTION .................................................................................................... 61 MATERIAL AND METHODS .................................................................................... 64 Specimens ................................................................................................................. 64 Image acquisition ...................................................................................................... 65 Environmental variables ........................................................................................... 65 Spatial analysis .......................................................................................................... 66 Outline analysis of teeth ........................................................................................... 67 Statistical analysis of tooth size and shape ............................................................... 68 Geometric morphometric analysis of skulls.............................................................. 70 Statistical analysis of skull size and shape: ............................................................... 71 Evaluation of size proxies .......................................................................................... 72 Software .................................................................................................................... 72 RESULTS ............................................................................................................... 73 Sexual Dimorphism ................................................................................................... 73 Spatial analysis .......................................................................................................... 73 Relation of tooth size and skull size with other size estimators ............................... 73 First upper molar size ................................................................................................ 74 2 First upper molar shape ............................................................................................ 75 Skull size .................................................................................................................... 77 Skull shape ................................................................................................................ 78 DISCUSSION ......................................................................................................... 80 Tooth ......................................................................................................................... 80 Skull ........................................................................................................................... 84 ACKNOWLEDGEMENTS ......................................................................................... 89 REFERENCES ......................................................................................................... 90 TABLES ............................................................................................................... 101 FIGURES ............................................................................................................. 106 Appendix A ........................................................................................................ 114 GENERAL CONCLUSION ................................................................................ 116 REFERENCES ....................................................................................................... 117 3 Abstract Environmental heterogeneity has long been associated with morphological variation in small mammals. Studies of ecotypic variation across time and space provide valuable information about the way organisms’ phenotypes respond to changing environmental conditions and the major factors influencing morphological changes, providing insight into the mechanisms that promote adaptation. In this thesis, I quantified morphological variation among 12 populations of the widespread and abundant southern red-backed vole, and examined the degree to which climate, primary productivity and ecozones explained variation in the morphological traits. Teeth and skulls of voles collected in several locations along a 1,000 km latitudinal gradient in Québec and Western Labrador were studied using geometric morphometric methods, and the relations between morphology and environmental and spatial variables were examined. Most of the spatial variation in morphology was correlated with environmental gradients. The morphological differentiation among populations could be explained by the environmental differences between their habitats, and precipitation and ecozone were the environmental variables mostly correlated with morphological variation. 4 Résumé L'hétérogénéité de l'environnement a depuis longtemps été associée à la variation morphologique chez les petits mammifères. Les études de la variation écotypique dans le temps et dans l'espace fournissent des informations utiles sur la réponse du phénotype des organismes aux variations des conditions environnementales, sur les principaux facteurs qui influencent les changements morphologiques, et sur les mécanismes qui favorisent l'adaptation. Cette étude examine les réponses morphologiques d'un mammifère généraliste et abondant, le campagnol a dos roux de Gapper, à la variation du climat, de la productivité, et des écozones. Les dents et les crânes de campagnols échantillonnés à plusieurs sites le long d'un gradient de 1000 km de latitude au Québec et a l'Ouest du Labrador ont été étudiés en utilisant des méthodes de morphométrie
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