The influence of mating systems
on morphological and
physiological divergence in bats
(Chiroptera)
Karen Acree, Jacqueline Ho, Harald Parzer, Mayté Ruiz
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
• By imposing or relaxing a constraint
evolution could go into different directions
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
•Mating system could relax or impose a constraint: e.g. in polygamous
species there is sexual dimorphism (overrides natural selection)
bigger testes,
smaller brain
polygamy
Chiroptera (bats)
•
•
•
•
High species diversity
Phylogeny well studied
Diverse mating systems
Adaptive radiation in feeding habits
http://www.nationaltrust.org.ky/info/bats.html
Larger brains
Mating
(♀) system
Monogamy
?
Diet
Fruit-eaters
Pitnick et al 2006, Jones and MacLarnon 2004, Eisenberg and Wilson 1978
(1) Does diet in bats relate
to their mating system?
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
Diet and Morphology
Insectivore
Frugivore
www.skullsunlimited.com
Mating System and Physiology
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)
Monogamous vs. Polygamous
•
http://animaldiversity.ummz.umich.edu
•
www.cbmall-gateway.com/bats/heartnosed_bat.html
•
http://filin.vn.ua/image/bat/s.leptura.jpg
•
•
http://animaldiversity.ummz.umich.edu
www.ecologyasia.com/images-k-z/lesser-woolly-horseshoe_00821.jpg
Lavia frons
(Megadermitidae):
African Yellowwinged 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 longfingered bat
Balantiopteryx plicata
(Emballonuridae): gray
sac-winged bat
http://animaldiversity.ummz.umich.edu
http://animaldiversity.ummz.umich.edu
http://www.worlddeer.org/britishbats/daubentons.html
http://animaldiversity.ummz.umich.edu
http://animaldiversity.ummz.umich.edu
(2) Do mating systems
affect basal stress
levels?
Stress
+
Hypothalamus (PVN)
-
Hippocampus
+
CRH and AVP
Anterior pituitary
-
Cortisol
+
ACTH
Adrenal gland
-
Cortisol
Immune Cells
Raison & Miller (2003)
Take blood samples and perform enzyme immunoassays (EIA)
Non-breeding
season
Breeding season
Monogamous ♂♀
Polygamous ♂♀
[CORT ]
[CORT ]
[CORT ]
[CORT ]
Determine ∆ [CORT] (from non-breeding to breeding seasons)
(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
Elucidate causes
by testing both
reproductive and
non-reproductive
females.
http://www.enature.com/fieldguides/enlarged.asp?imageID=18884
Martin et al 2004, Lampe 1999, Nantz et al 2006
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
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.
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.
Questions?