Published on August 2, 2007
The influence of mating systems on morphological and physiological divergence in bats (Chiroptera): The influence of mating systems on morphological and physiological divergence in bats (Chiroptera) Karen Acree, Jacqueline Ho, Harald Parzer, Mayté Ruiz Evolution and Constraints: Evolution and Constraints Why are some traits stable and others not? Constraints – phenotypic space (directions in which evolution could lead) is diminished Inheritance Selection Development (e.g. due to pleiotropic effects) Design limits (Arnold, 1992) Evolution and Constraints: Evolution and Constraints By imposing or relaxing a constraint evolution could go into different directions Evolution of Mating Systems: Evolution of Mating Systems Explained by the interface of sexual selection and ecological factors Reproductive success of ♂ is limited by the amount of ♀ ♂ should monopolize as many ♀ as possible ♀ distribution depends on the distribution of key resources: scarce and not clumped or scarce and clumped Scarce and clumped: polygamy Scarce and not clumped: monogamy (Emlen and Oring, 1977) Evolution in Mating Systems: Evolution in Mating Systems Mating system could relax or impose a constraint: e.g. in polygamous species there is sexual dimorphism (overrides natural selection) polygamy bigger testes, smaller brain Slide6: Chiroptera (bats) High species diversity Phylogeny well studied Diverse mating systems Adaptive radiation in feeding habits http://www.nationaltrust.org.ky/info/bats.html Slide7: Mating system Fruit-eaters Larger brains (♀) Monogamy ? Diet ? Pitnick et al 2006, Jones and MacLarnon 2004, Eisenberg and Wilson 1978 Slide8: (1) Does diet in bats relate to their mating system? Method: COMPARE: Method: COMPARE Collect information on the mating system and eating habits of several hundred species of chiroptera - literature search -standardized questionnaire to active field workers Analyze data using the COMPARE software program Martins 2004 Slide10: www.skullsunlimited.com Insectivore Frugivore Diet and Morphology Testing the effect of mating systems on basal stress levels and immune function: Testing the effect of mating systems on basal stress levels and immune function 10 species were chosen: 5 monogamous 5 polygamous (Leks, mating aggregations/swarming) Mating System and Physiology Monogamous vs. Polygamous: Monogamous vs. Polygamous Lavia frons (Megadermitidae):African Yellow-winged bat Cardioderma cor (Megadermitidae): Heart-nosed bat/ African false vampire bat Saccopteryx leptura (Eballonuridae): lesser sac-winged bat Hipposideros beatus (Rhinolophidae): Benito roundleaf bat Rhinolophus sedulous (Rhinolophidae): lesser woolly horseshoe bat Hypsignathus monstrosus (Pteropodidae): African hammerhead bat Myotis sodalis (Vespertilionidae): Indiana Bat Myotis daubentoni (Vespertilionidae): water bat/ Daubenton’s bat Miniopterus schreibersii (Vespertilionidae): Schreibers's long-fingered bat Balantiopteryx plicata (Emballonuridae): gray sac-winged bat Slide13: (2) Do mating systems affect basal stress levels? Slide14: Stress Hypothalamus (PVN) Anterior pituitary Adrenal gland Immune Cells Hippocampus Raison andamp; Miller (2003) - - - - + + + Slide15: Monogamous ♂♀ Polygamous ♂♀ Non-breeding season Breeding season [CORT ] [CORT ] [CORT ] [CORT ] Take blood samples and perform enzyme immunoassays (EIA) Determine ∆ [CORT] (from non-breeding to breeding seasons) Slide16: (3) Do differences in mating system affect immune responses? Monogamy and immune function: Multiple matings may incur a cost to females If diet is in fact correlated with mating system, fruit may have a positive association with immunity http://www.enature.com/fieldguides/enlarged.asp?imageID=18884 Elucidate causes by testing both reproductive and non-reproductive females. Monogamy and immune function Martin et al 2004, Lampe 1999, Nantz et al 2006 Method: Measure cell-mediated immunity : Method: Measure cell-mediated immunity Delayed-type hypersensitivity Inject with phytohaemagglutinin prime Measure swelling http://www.nature-shetland.co.uk/naturelatest/pics/nat%20the%20bat.jpg Concluding remarks: Concluding remarks Thus, new phenotypic traits can emerge when the constraint of polygamy is lifted. These new traits need not directly relate to monogamy. This allows us to elucidate whether mating system constraints directionally influence morphological and physiological change. COMPARE will show if a relationship exists between mating system and feeding habits, which may then lead to morphological differences. Stress and immune measures will demonstrate whether mating systems induce physiological changes. Slide20: Questions?