Rights statement: This is a post-print of an article published in Journal of Animal Ecology, 81 (1), 2012. (c) Wiley.
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Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - Testes size, testosterone production and reproductive behaviour in a natural mammalian mating system
AU - Preston, Brian T.
AU - Stevenson, Ian R.
AU - Lincoln, Gerald A.
AU - Monfort, Steven L.
AU - Pilkington, Jill G.
AU - Wilson, Kenneth
N1 - This is a post-print of an article published in Journal of Animal Ecology, 81 (1), 2012. (c) Wiley.
PY - 2012/1
Y1 - 2012/1
N2 - 1. Testosterone (T) is a key mediator in the expression of numerous morphological and behavioural traits in mammals, but the factors underlying individual variation in circulating T levels are poorly understood.2. The intimate structural integration of sperm and T production within the testes, alongside the dependency of sperm production on high levels of T, suggests that T requirements for spermatogenesis could be an important driver of individual differences in T.3. To test this hypothesis, we examine how male capacity for sperm production ( as indicated by their testes size) is associated with T levels in a feral population of Soay sheep, resident on St. Kilda, Scotland, during their rutting season.4. We found a strong positive relationship between an individual's testes size ( as measured before their seasonal enlargement) and the levels of circulating T during their rut, suggesting that T requirements for spermatogenesis has a prominent influence on the production of this androgen.5. In contrast, body condition and competitive ability did not independently predict T levels, findings that are inconsistent with conventional 'condition-dependent' and 'challenge' hypotheses of T production.6. This influence of male's capacity for sperm production on T appeared to be substantial enough to be biologically relevant, as testes size also predicted male aggression and mate-seeking behaviour.7. Our results suggest that a male's inherent capacity for sperm and T production is tightly phenotypically integrated, with potential consequences for a wide range of other T-mediated reproductive traits.
AB - 1. Testosterone (T) is a key mediator in the expression of numerous morphological and behavioural traits in mammals, but the factors underlying individual variation in circulating T levels are poorly understood.2. The intimate structural integration of sperm and T production within the testes, alongside the dependency of sperm production on high levels of T, suggests that T requirements for spermatogenesis could be an important driver of individual differences in T.3. To test this hypothesis, we examine how male capacity for sperm production ( as indicated by their testes size) is associated with T levels in a feral population of Soay sheep, resident on St. Kilda, Scotland, during their rutting season.4. We found a strong positive relationship between an individual's testes size ( as measured before their seasonal enlargement) and the levels of circulating T during their rut, suggesting that T requirements for spermatogenesis has a prominent influence on the production of this androgen.5. In contrast, body condition and competitive ability did not independently predict T levels, findings that are inconsistent with conventional 'condition-dependent' and 'challenge' hypotheses of T production.6. This influence of male's capacity for sperm production on T appeared to be substantial enough to be biologically relevant, as testes size also predicted male aggression and mate-seeking behaviour.7. Our results suggest that a male's inherent capacity for sperm and T production is tightly phenotypically integrated, with potential consequences for a wide range of other T-mediated reproductive traits.
KW - aggression
KW - challenge hypothesis
KW - condition dependence
KW - sexual behaviour
KW - Soay sheep
KW - sperm competition
KW - SPERM COMPETITION
KW - MATE CHOICE
KW - DOMESTICATED BREEDS
KW - COPULATORY-BEHAVIOR
KW - TESTICULAR ACTIVITY
KW - SEASONAL CYCLES
KW - SEXUAL-BEHAVIOR
KW - SOAY SHEEP
KW - ANDROGEN
KW - RAMS
UR - http://www.scopus.com/inward/record.url?scp=83155181863&partnerID=8YFLogxK
U2 - 10.1111/j.1365-2656.2011.01907.x
DO - 10.1111/j.1365-2656.2011.01907.x
M3 - Journal article
VL - 81
SP - 296
EP - 305
JO - Journal of Animal Ecology
JF - Journal of Animal Ecology
SN - 0021-8790
IS - 1
ER -