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Testing evolutionary models of senescence in a natural population: age and inbreeding effects on fitness components in song sparrows.

Keller LF, Reid JM, Arcese P - Proc. Biol. Sci. (2008)

Bottom Line: We use pedigree and life-history data from free-living song sparrows (Melospiza melodia) to test for additive and interactive effects of age and individual inbreeding coefficient (f) on fitness components, and thereby assess the evidence for MA.These analyses therefore provide mixed support for MA.We discuss the strengths and limitations of such analyses and therefore the value of natural pedigreed populations in testing evolutionary models of senescence.

View Article: PubMed Central - PubMed

Affiliation: Zoological Museum, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland. lukas.keller@zm.uzh.ch

ABSTRACT
Mutation accumulation (MA) and antagonistic pleiotropy (AP) have each been hypothesized to explain the evolution of 'senescence' or deteriorating fitness in old age. These hypotheses make contrasting predictions concerning age dependence in inbreeding depression in traits that show senescence. Inbreeding depression is predicted to increase with age under MA but not under AP, suggesting one empirical means by which the two can be distinguished. We use pedigree and life-history data from free-living song sparrows (Melospiza melodia) to test for additive and interactive effects of age and individual inbreeding coefficient (f) on fitness components, and thereby assess the evidence for MA. Annual reproductive success (ARS) and survival (and therefore reproductive value) declined in old age in both sexes, indicating senescence in this short-lived bird. ARS declined with f in both sexes and survival declined with f in males, indicating inbreeding depression in fitness. We observed a significant agexf interaction for male ARS (reflecting increased inbreeding depression as males aged), but not for female ARS or survival in either sex. These analyses therefore provide mixed support for MA. We discuss the strengths and limitations of such analyses and therefore the value of natural pedigreed populations in testing evolutionary models of senescence.

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Related in: MedlinePlus

Age-specific variation in (year-standardized) annual adult survival in (a) female and (b) male song sparrows. Martingale residuals of a  model adjusting for hatch year are shown, smoothed using a cubic spline.
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fig2: Age-specific variation in (year-standardized) annual adult survival in (a) female and (b) male song sparrows. Martingale residuals of a model adjusting for hatch year are shown, smoothed using a cubic spline.

Mentions: Survival declined markedly with age in males and females, with no clear evidence of nonlinear effects (figure 2; table 2). The apparent levelling off in hazard in old females was not significant (p>0.44) and reflects a very small sample size (n=4) of females aged 7 or more years. Average reproductive values declined markedly in old age in both sexes (figure 3).


Testing evolutionary models of senescence in a natural population: age and inbreeding effects on fitness components in song sparrows.

Keller LF, Reid JM, Arcese P - Proc. Biol. Sci. (2008)

Age-specific variation in (year-standardized) annual adult survival in (a) female and (b) male song sparrows. Martingale residuals of a  model adjusting for hatch year are shown, smoothed using a cubic spline.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2366077&req=5

fig2: Age-specific variation in (year-standardized) annual adult survival in (a) female and (b) male song sparrows. Martingale residuals of a model adjusting for hatch year are shown, smoothed using a cubic spline.
Mentions: Survival declined markedly with age in males and females, with no clear evidence of nonlinear effects (figure 2; table 2). The apparent levelling off in hazard in old females was not significant (p>0.44) and reflects a very small sample size (n=4) of females aged 7 or more years. Average reproductive values declined markedly in old age in both sexes (figure 3).

Bottom Line: We use pedigree and life-history data from free-living song sparrows (Melospiza melodia) to test for additive and interactive effects of age and individual inbreeding coefficient (f) on fitness components, and thereby assess the evidence for MA.These analyses therefore provide mixed support for MA.We discuss the strengths and limitations of such analyses and therefore the value of natural pedigreed populations in testing evolutionary models of senescence.

View Article: PubMed Central - PubMed

Affiliation: Zoological Museum, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland. lukas.keller@zm.uzh.ch

ABSTRACT
Mutation accumulation (MA) and antagonistic pleiotropy (AP) have each been hypothesized to explain the evolution of 'senescence' or deteriorating fitness in old age. These hypotheses make contrasting predictions concerning age dependence in inbreeding depression in traits that show senescence. Inbreeding depression is predicted to increase with age under MA but not under AP, suggesting one empirical means by which the two can be distinguished. We use pedigree and life-history data from free-living song sparrows (Melospiza melodia) to test for additive and interactive effects of age and individual inbreeding coefficient (f) on fitness components, and thereby assess the evidence for MA. Annual reproductive success (ARS) and survival (and therefore reproductive value) declined in old age in both sexes, indicating senescence in this short-lived bird. ARS declined with f in both sexes and survival declined with f in males, indicating inbreeding depression in fitness. We observed a significant agexf interaction for male ARS (reflecting increased inbreeding depression as males aged), but not for female ARS or survival in either sex. These analyses therefore provide mixed support for MA. We discuss the strengths and limitations of such analyses and therefore the value of natural pedigreed populations in testing evolutionary models of senescence.

Show MeSH
Related in: MedlinePlus