SPERM COMPETITION AND MALE SOCIAL DOMINANCE IN THE BANK VOLE (MYODES GLAREOLUS) Thesis submitted in accordance with the requirements of the University of Liverpool for the degree of Doctor in Philosophy by Jean-Fran^ois Lemaitre 1 Table of contents List of Tables.......................................................................................................................................6 List of Figures.....................................................................................................................................8 Declaration of work conducted.................................................................................................... 10 Abstract ......................................................................................................................................13 Chapter 1: General introduction............................................................................................... 15 1.1 Chapter overview........................................................................................................... 15 1.2 Sexual selection..... .......................................................................................................... 15 (a) Sexual selection............................................................................................................... 15 (b) Sexual selection and sex-roles........................................................................................16 (c) Pre-copulatory sexual selection......................................................................................18 (d) Female multiple mating and sperm competition..........................................................19 (e) Sperm competition, cryptic female choice and sexual conflict................................. 20 1.3 Sperm competition: theory and empiry............................... ........................................ 21 (a) Evolutionary consequences of sperm competition......................................................21 (b) Sperm competition in mammals............................................. 22 i) Testis size, sperm morphology and motility.................................................................23 ii) Copulatory behaviour..................................................................................................... 25 (c) Sperm competition games...............................................................................................27 i) Risk and intensity models...............................................................................................28 ii) Raffles and roles models........................... 29 (d) Sperm allocation in mammals...................... 30 1.4 Sexual selection and social dominance in mammals...................................................32 (a) Social dominance in mammals...................................................................................... 32 (b) Effect of dominance on mating success........................................................................ 33 1.5 Bank voles {Myodes glareolus)...................................................................................... 34 (a) Ecology and population dynamics.................................................................................34 (b) Reproductive characteristics...........................................................................................35 (c) Social dominance and mate choice................................................................................35 (d) Sperm competition...........................................................................................................36 1.6 Thesis overview................................................................................................................37 Chapter 2: Male mate choice in the bank vole in relation to social dominance and level of sperm depletion...........................................................................................................................39 2.1 Chapter overview.............................................................................................................39 2.2 Introduction...................................................................................................................... 40 (a) Male mate choice.............................................................................................................40 (b) Female quality.................................................................................................................41 (c) Inbreeding avoidance...................................................................................................... 41 2.3 Methods.............................................................................................................................44 (a) Subjects...................................................................... 44 2 (b) Social dominance establishment.............................................................................44 (c) Quantifying inbreeding avoidance behaviour......................................................... 47 (d) Statistical analysis...................................................................................................49 2.4 Results................................................................................................................... 49 (a) Male inbreeding avoidance behaviour and social status...........................................49 (b) Effects of sperm depletion......................................................................................50 2.5 Discussion...............................................................................................................54 2.6 Conclusion...............................................................................................................56 Chapter 3: Genital morphology and allometry in the bank vole......................................57 3.1 Chapter overview....................................................................................................57 3.2 Introduction.............................................................................................................58 (a) Structure and diversity of genitalia in mammals.................................................... 58 (b) Sexual selection and genital allometry................................................................... 58 (c) Functions of genitalia in mammals.........................................................................60 (d) Allometry................................................................................................................61 (e) Aim of the study.....................................................................................................62 3.3 Methods...................................................................................................................66 (a) Subjects...................................................................................................................66 (b) Social dominance establishment.............................................................................67 (c) Mating trials........................................................................................................... 68 (d) Copulatory behaviour and litter size....................................................................... 68 (e) Preparation and measurement of bacula, spines and metatarsal bones...................69 (f) Preparation and measurement of penile spines....................................................... 70 (g) Statistical analysis...................................................................................................73 3.4 Results.....................................................................................................................74 (a) Genital morphology, litter size and male social status........................................... 75 (b) Genital morphology, copulatory behaviour and male social status.........................76 (c) Allometry and phenotypic variation....................................................................... 78 3.5 Discussion...............................................................................................................80 (a) Male social status and genitalia morphology.......................................................... 80 (b) Allometry and phenotypic variation in bank voles................................................. 82 3.6 Conclusion...............................................................................................................83 Chapter 4: Sperm allocation under assigned roles in the bank vole................................ 85 4.1 Chapter overview....................................................................................................85 4.2 Introduction........................................................................ 86 (a) Sperm allocation.....................................................................................................86 (b) Sperm allocation, copulatory behaviour and male social status..............................87 (c) Aim of the study.....................................................................................................88 4.3 Methods...................................................................................................................89 (a) Subjects...................................................................................................................89