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Ecological, evolutionary and social constraints on reproductive effort: are hoary marmots really biennial breeders?

Patil VP, Karels TJ, Hik DS - PLoS ONE (2015)

Bottom Line: Hoary marmots were neither obligate nor facultative biennial breeders, and breeding probability was insensitive to evolved, environmental, or social factors.However, newly mature females were significantly less likely to breed than older individuals.Annual breeding did not result in increased mortality.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, Alaska, 99775, United States of America; Department of Biological Sciences, University of Alberta, Edmonton, AB, T6G 2E9, Canada.

ABSTRACT
Biennial breeding is a rare life-history trait observed in animal species living in harsh, unproductive environments. This reproductive pattern is thought to occur in 10 of 14 species in the genus Marmota, making marmots useful model organisms for studying its ecological and evolutionary implications. Biennial breeding in marmots has been described as an obligate pattern which evolved as a mechanism to mitigate the energetic costs of reproduction (Evolved Constraint hypothesis). However, recent anecdotal evidence suggests that it is a facultative pattern controlled by annual variation in climate and food availability (Environmental Constraint hypothesis). Finally, in social animals like marmots, biennial breeding could result from reproductive competition between females within social groups (Social Constraint hypothesis). We evaluated these three hypotheses using mark-recapture data from an 8-year study of hoary marmot (Marmota caligata) population dynamics in the Yukon. Annual variation in breeding probability was modeled using multi-state mark-recapture models, while other reproductive life-history traits were modeled with generalized linear mixed models. Hoary marmots were neither obligate nor facultative biennial breeders, and breeding probability was insensitive to evolved, environmental, or social factors. However, newly mature females were significantly less likely to breed than older individuals. Annual breeding did not result in increased mortality. Female survival and, to a lesser extent, average fecundity were correlated with winter climate, as indexed by the Pacific Decadal Oscillation. Hoary marmots are less conservative breeders than previously believed, and the evidence for biennial breeding throughout Marmota, and in other arctic/alpine/antarctic animals, should be re-examined. Prediction of future population dynamics requires an accurate understanding of life history strategies, and of how life history traits allow animals to cope with changes in weather and other demographic influences.

No MeSH data available.


Related in: MedlinePlus

The Relationship between body condition and day of year for breeding and non-breeding female hoary marmots.We estimated the change over time in the body condition index (residuals from a linear regression of body mass as a function of zygomatic arch width) of non-breeding and breeding female hoary marmots in the Ruby Range, Yukon. Data from 1999–2004 are shown pooled across years. The best fit lines for linear regressions are shown. The slope of the relationship between body condition and Julian day was 0.02 (SE = 0.0016) for breeders and 0.028 (SE = 0.0015) for nonbreeders. The effects of day, breeding state, and day * breeding state interaction were all significant (p < 0.005) in a general linear model. Overall the model had an adjusted R2 of 0.62.
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pone.0119081.g003: The Relationship between body condition and day of year for breeding and non-breeding female hoary marmots.We estimated the change over time in the body condition index (residuals from a linear regression of body mass as a function of zygomatic arch width) of non-breeding and breeding female hoary marmots in the Ruby Range, Yukon. Data from 1999–2004 are shown pooled across years. The best fit lines for linear regressions are shown. The slope of the relationship between body condition and Julian day was 0.02 (SE = 0.0016) for breeders and 0.028 (SE = 0.0015) for nonbreeders. The effects of day, breeding state, and day * breeding state interaction were all significant (p < 0.005) in a general linear model. Overall the model had an adjusted R2 of 0.62.

Mentions: The body condition index of non-breeding females increased faster over the course of the summer than that of breeders (Fig. 3). The slope of the relationship between body condition and Julian day was 0.02 (SE = 0.0016) for breeders and 0.028 (SE = 0.0015) for nonbreeders. In a general linear model of body condition index as a function of Julian day, breeding state, and an interaction term, all three terms were highly significant (p<0.005). The overall model had an adjusted R2 of 0.62. On average, nonbreeders had higher body condition scores (greater body mass relative to skeletal size) at the end of August than breeders (Fig. 3).


Ecological, evolutionary and social constraints on reproductive effort: are hoary marmots really biennial breeders?

Patil VP, Karels TJ, Hik DS - PLoS ONE (2015)

The Relationship between body condition and day of year for breeding and non-breeding female hoary marmots.We estimated the change over time in the body condition index (residuals from a linear regression of body mass as a function of zygomatic arch width) of non-breeding and breeding female hoary marmots in the Ruby Range, Yukon. Data from 1999–2004 are shown pooled across years. The best fit lines for linear regressions are shown. The slope of the relationship between body condition and Julian day was 0.02 (SE = 0.0016) for breeders and 0.028 (SE = 0.0015) for nonbreeders. The effects of day, breeding state, and day * breeding state interaction were all significant (p < 0.005) in a general linear model. Overall the model had an adjusted R2 of 0.62.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4359141&req=5

pone.0119081.g003: The Relationship between body condition and day of year for breeding and non-breeding female hoary marmots.We estimated the change over time in the body condition index (residuals from a linear regression of body mass as a function of zygomatic arch width) of non-breeding and breeding female hoary marmots in the Ruby Range, Yukon. Data from 1999–2004 are shown pooled across years. The best fit lines for linear regressions are shown. The slope of the relationship between body condition and Julian day was 0.02 (SE = 0.0016) for breeders and 0.028 (SE = 0.0015) for nonbreeders. The effects of day, breeding state, and day * breeding state interaction were all significant (p < 0.005) in a general linear model. Overall the model had an adjusted R2 of 0.62.
Mentions: The body condition index of non-breeding females increased faster over the course of the summer than that of breeders (Fig. 3). The slope of the relationship between body condition and Julian day was 0.02 (SE = 0.0016) for breeders and 0.028 (SE = 0.0015) for nonbreeders. In a general linear model of body condition index as a function of Julian day, breeding state, and an interaction term, all three terms were highly significant (p<0.005). The overall model had an adjusted R2 of 0.62. On average, nonbreeders had higher body condition scores (greater body mass relative to skeletal size) at the end of August than breeders (Fig. 3).

Bottom Line: Hoary marmots were neither obligate nor facultative biennial breeders, and breeding probability was insensitive to evolved, environmental, or social factors.However, newly mature females were significantly less likely to breed than older individuals.Annual breeding did not result in increased mortality.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, Alaska, 99775, United States of America; Department of Biological Sciences, University of Alberta, Edmonton, AB, T6G 2E9, Canada.

ABSTRACT
Biennial breeding is a rare life-history trait observed in animal species living in harsh, unproductive environments. This reproductive pattern is thought to occur in 10 of 14 species in the genus Marmota, making marmots useful model organisms for studying its ecological and evolutionary implications. Biennial breeding in marmots has been described as an obligate pattern which evolved as a mechanism to mitigate the energetic costs of reproduction (Evolved Constraint hypothesis). However, recent anecdotal evidence suggests that it is a facultative pattern controlled by annual variation in climate and food availability (Environmental Constraint hypothesis). Finally, in social animals like marmots, biennial breeding could result from reproductive competition between females within social groups (Social Constraint hypothesis). We evaluated these three hypotheses using mark-recapture data from an 8-year study of hoary marmot (Marmota caligata) population dynamics in the Yukon. Annual variation in breeding probability was modeled using multi-state mark-recapture models, while other reproductive life-history traits were modeled with generalized linear mixed models. Hoary marmots were neither obligate nor facultative biennial breeders, and breeding probability was insensitive to evolved, environmental, or social factors. However, newly mature females were significantly less likely to breed than older individuals. Annual breeding did not result in increased mortality. Female survival and, to a lesser extent, average fecundity were correlated with winter climate, as indexed by the Pacific Decadal Oscillation. Hoary marmots are less conservative breeders than previously believed, and the evidence for biennial breeding throughout Marmota, and in other arctic/alpine/antarctic animals, should be re-examined. Prediction of future population dynamics requires an accurate understanding of life history strategies, and of how life history traits allow animals to cope with changes in weather and other demographic influences.

No MeSH data available.


Related in: MedlinePlus