Extra-pair paternity and the evolution of testis size in a behaviorally monogamous tropical mammal,the large treeshrew (<Emphasis Type="Italic">Tupaia tana</Emphasis>) |
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Authors: | Jason Munshi-South |
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Institution: | (1) Program in Behavior, Ecology, Evolution and Systematics (BEES), Department of Biology, University of Maryland, College Park, MD 20742, USA;(2) Present address: Department of Natural Sciences, Baruch College, City University of New York, 17 Lexington Avenue, New York, NY 10010, USA |
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Abstract: | Monogamy is rare in mammals (<5% spp.) but occurs in greater frequency among primates (15%) and their close relatives, the
treeshrews (100%; Order: Scandentia). Two genetic studies of parentage in monogamous primates revealed high rates of extra-pair
paternity (EPP), but to date parentage has not been studied in a treeshrew species. I analyzed the genetic parentage of 22
offspring from two populations of large treeshrews in Sabah, Malaysia (NE Borneo), using seven autosomal microsatellite loci
and one mitochondrial DNA marker. Half of these offspring were sired by males that were not the presumed partner of the mother
(50% EPP), and three litters exhibited evidence of multiple paternity. However, comparative analysis indicated that the high
rate of EPP in Tupaia tana is not associated with intense sperm competition. Relative testis size of treeshrews was similar to testis size in 22 primate
species with uni-male mating systems but smaller than 44 primates with multi-male mating systems. After factoring out the
effects of body size and phylogeny, I also found that the evolution of multi-male mating systems was significantly associated
with the evolution of larger testis size. Male–female pairs of T. tana occupy joint territories but forage and sleep alone (“dispersed pair-living”), and I argue that this form of behavioral monogamy
renders mate guarding ineffective. The adaptive advantages of behavioral monogamy likely differ from the advantages driving
EPP in large treeshrews. However, small testis size suggests that behavioral monogamy is not masking a dispersed multi-male
mating system in this species. |
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Keywords: | Extra-pair paternity Monogamy Testis size Treeshrews Borneo |
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