Mammals in Which Females are Larger Than Males

Ralls, Katherine

doi:10.1086/409310

Cited by 648 publications

(338 citation statements)

References 100 publications

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“…In many mammalian species, including primates, males are typically larger than females and have to cope with high costs of body maintenance (Ralls, 1976; reviewed in Key & Ross, 1999). However, in some species there is little sexual dimorphism in size, including the majority of Lemuriformes (Jolly, 1984; Kappeler, 1990, 1991).…”

Section: Introductionmentioning

confidence: 99%

Sex and seasonal differences in diet and nutrient intake in Verreaux's sifakas (Propithecus verreauxi)

Koch

Ganzhorn

Rothman

et al. 2016

American J Primatol

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Fluctuations in food availability are a major challenge faced by primates living in seasonal climates. Variation in food availability can be especially challenging for females, because of the high energetic costs of reproduction. Therefore, females must adapt the particular demands of the different reproductive stages to the seasonal availability of resources. Madagascar has a highly seasonal climate, where food availability can be extremely variable. We investigated the seasonal changes in diet composition, nutrient and energy intake of female and male sifakas (Propithecus verreauxi) in a dry deciduous forest in western Madagascar. We examined how females adjust their diet to different reproductive stages. Seasonality affected the diet of both sexes; particularly in the dry season (Apr–Oct) with low availability of food items, especially fruits, males and females had a reduced nutrient and energy intake compared to the wet season (Nov–Mar) with higher food and fruit availability. The comparison of the diet between sexes in different reproductive stages showed that during the late stage of lactation (Nov–Jan) females had higher food intake, and as a result they had a higher intake of macronutrients (crude protein, fat and non‐structured carbohydrates (TNC)) and energy than males. These differences were not present during the pregnancy of females, with both sexes having similar intake of macronutrients and energy during that stage. The increase in the intake of macronutrients observed for females during late lactation could be related to the higher energetic demands of this stage of reproduction. Thus, the observed pattern in the diet indicates that sifaka females are following a capital breeding strategy, whereby females potentially store enough nutrients to cope with the reproduction costs in periods of low food availability.

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Section: Introductionmentioning

confidence: 99%

Sex and seasonal differences in diet and nutrient intake in Verreaux's sifakas (Propithecus verreauxi)

Koch

Ganzhorn

Rothman

et al. 2016

American J Primatol

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“…Body size is correlated with many life history traits and can be the target of both sexual and natural selection (Blackburn et al 1999). In many mammals and birds SSD is male biased, but in the majority of ectotherms, it is female biased, although with many exceptions (Ralls 1976, Andersson 1994, Monnet & Cherry 2002, Schulte-Hostedde et al 2002, Teder & Tammaru 2005. Differences between females and males in the intensity and/or direction of sexual selection can generate differences in SSD (Darwin 1871;Spencer & Masters 1992;Andersson 1994;Fairbairn & Preziosi 1994;Ding & Blanckenhorn 2002;Kraushaar & Blanckenhorn 2002;Szekely et al 2004;Teder & Tammaru 2005, 2005.…”

Section: Introductionmentioning

confidence: 99%

Size-Dependent Selection on Arrival Times in Sticklebacks: Why Small Males Arrive First

Candolin

Voigt

2003

Evolution

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Studies on arrival time to breeding areas show that high‐quality males usually arrive first and gain the highest reproductive success. This is generally assumed to be due to phenotype‐dependent costs and benefits of early arrival. We show that the opposite arrival order can occur, probably due to selection on poor‐quality males to increase their chances of reproduction. In a fish species, the threespine stickleback, Gasterosteus aculeatus, small males arrived before larger males at the breeding grounds. Early arrival was costly because predation risk was at its highest at the start of the season and early territory establishment was selected against, as demonstrated by selection coefficients for territory maintenance and hatching success. Large males probably postponed arrival until females were available to decrease predation risk costs and increase offspring production. An experimental study showed that a delay in arrival of large males does not decrease their probability of reproduction, because large males are able to take over nest sites from small males. Small males, on the other hand, are less likely to establish territories in competition with large males but can pay the costs of early arrival in exchange for the benefit of access to territories. Thus, whereas natural selection favors later arrival, sexual selection through competition for breeding territories favors early arrival in small, competitively inferior males. This results in the benefits of early arrival depending on the competitive ability of the male, which favors size‐dependent optimal arrival times.

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“…On one hand, sexual dimorphism is regarded as an outcome of sex-specific patterns of current sexual and natural selection (e.g., Darwin 1871;Ralls 1976;Lande 1980;Slatkin 1984;Arak 1988;Shine 1989). Indeed, concordance between current environmental conditions and degree of dimorphism is well documented (e.g., Earhart and Johnson 1970;Johnston and Fleischer 1981;Payne 1984;Moore 1990;Webster 1992;Promislow et al 1994;Martin and Badyaev 1996;Mitani et al 1996;Badyaev 1997a,b;Poulin 1997;Wikelski and Trillmich 1997).…”

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confidence: 99%

Sexual Dimorphism in Relation to Current Selection in the House Finch

Badyaev¹,

Martin

2000

Evolution

104

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Abstract. Sexual dimorphism is thought to have evolved in response to selection pressures that differ between males and females. Our aim in this study was to determine the role of current net selection in shaping and maintaining contemporary sexual dimorphism in a recently established population of the house finch (Carpodacus mexicanus) in Montana. We found strong differences between sexes in direction of selection on sexually dimorphic traits, significant heritabilities of these traits, and a close congruence between current selection and observed sexual dimorphism in Montana house finches. Strong directional selection on sexually dimorphic traits and similar intensities of selection in each sex suggested that sexual dimorphism arises from adaptive responses in males and females, with both sexes being far from their local fitness optimum. This pattern is expected when a recently established population experiences continuous immigration from ecologically distinct areas of a species range or as a result of widely fluctuating selection pressures, as found in our study. Strong and sexually dimorphic selection pressures on heritable morphological traits, in combination with low phenotypic and genetic covariation among these traits during growth, may have accounted for close congruence between current selection and observed sexual dimorphism in the house finch. This conclusion is consistent with the profound adaptive population divergence in sexual dimorphism that accompanied very successful colonization of most of the North America by the house finch over the last 50 years.Key words. Fecundity, house finch, local adaptation, overwinter survival, pairing success, peripheral population, sexual dimorphism.Received January 27, 1999. Accepted October 26, 1999.The relative importance of selection in evolution and maintenance of sexual dimorphism is a much debated issue. On one hand, sexual dimorphism is regarded as an outcome of sex-specific patterns of current sexual and natural selection (e

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Mammals in Which Females are Larger Than Males

Abstract: Females are larger than males in more species

Cited by 648 publications

References 100 publications

Sex and seasonal differences in diet and nutrient intake in Verreaux's sifakas (Propithecus verreauxi)

Sex and seasonal differences in diet and nutrient intake in Verreaux's sifakas (Propithecus verreauxi)

Size-Dependent Selection on Arrival Times in Sticklebacks: Why Small Males Arrive First

Sexual Dimorphism in Relation to Current Selection in the House Finch

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