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Zhou Y, Pan Y, Wang M, Wang X, Zheng X, Zhou Z. Fossil evidence sheds light on sexual selection during the early evolution of birds. Proc Natl Acad Sci U S A 2024; 121:e2309825120. [PMID: 38190528 PMCID: PMC10801838 DOI: 10.1073/pnas.2309825120] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2023] [Accepted: 11/16/2023] [Indexed: 01/10/2024] Open
Abstract
The impact of sexual selection on the evolution of birds has been widely acknowledged. Although sexual selection has been hypothesized as a driving force in the occurrences of numerous morphological features across theropod evolution, this hypothesis has yet to be comprehensively tested due to challenges in identifying the sex of fossils and by the limited sample size. Confuciusornis sanctus is arguably the best-known early avialan and is represented by thousands of well-preserved specimens from the Early Cretaceous Jehol lagerstätte, which provides us with a chance to decipher the strength of sexual selection on extinct vertebrates. Herein, we present a morphometric study of C. sanctus based on the largest sample size of this taxon collected up to now. Our results indicate that the characteristic elongated paired rectrices is a sexually dimorphic trait and statistically robust inferences of the sexual dimorphism in size, shape, and allometry that have been established, providing the earliest known sexual dimorphism in avian evolution. Our findings suggest that sexual selection, in conjunction with natural selection, does act upon body size and limb length ratio in early birds, thereby promoting a deeper understanding of the role of sexual selection in large-scale phylogenetic evolution.
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Affiliation(s)
- Yibo Zhou
- State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Centre for Research and Education on Biological Evolution and Environment and Frontiers Science Center for Critical Earth Material Cycling, Nanjing University, Nanjing210023, China
| | - Yanhong Pan
- State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Centre for Research and Education on Biological Evolution and Environment and Frontiers Science Center for Critical Earth Material Cycling, Nanjing University, Nanjing210023, China
| | - Min Wang
- Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing100044, China
| | - Xiaoli Wang
- Institute of Geology and Paleontology, Linyi University, Linyi276000, Shandong, China
- Shandong Tianyu Museum of Nature, Pingyi273300, Shandong, China
| | - Xiaoting Zheng
- Institute of Geology and Paleontology, Linyi University, Linyi276000, Shandong, China
- Shandong Tianyu Museum of Nature, Pingyi273300, Shandong, China
| | - Zhonghe Zhou
- Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing100044, China
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Yussif I, Kugonza DR, Okot MW, Amuge PO, Costa R, Dos Anjos F. Uganda chicken genetic resources: I. phenotypic and production characteristics. Front Genet 2023; 13:1033031. [PMID: 36761692 PMCID: PMC9902952 DOI: 10.3389/fgene.2022.1033031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Accepted: 12/29/2022] [Indexed: 01/25/2023] Open
Abstract
The extent of diversity in the indigenous chicken breeds of Uganda was assessed for their potential utilisation in breeding programmes. A total of 293 indigenous-chicken-keeping households in villages across 35 districts forming 12 sub-regions of the four regions were randomly sampled for 586 mature chickens of both sexes. While only 20.8% of households were headed by women, 40.6% of indigenous chicken keepers were women. The production objectives mainly focused on chickens as sources of income from sales and household food. The chickens were predominantly managed in a scavenging (94.2%) feeding system in a mainly (96.9%) mixed crop-livestock system. The average flock size was 19.80 ± 1.21 chickens with 3.83 ± 0.29 laying hens, each producing an average of 13.41 ± 0.20 eggs/clutch and 40.3 ± 0.6 eggs/annum of 5.20 ± 0.03-month egg production age. Normal-feather strains predominated (>90%), with scattered incidences of naked neck, frizzles, polydactyl, and ptilopody traits in both sexes. Dark (49.0% hen; 43.8% cock) and white (38.3% hen; 42.4% cock) skin colours were most common among the chickens compared to yellow skin. However, yellow-coloured shanks were proportionally the most observed (41% cock; 29% hen). Orange and brown iris (eye) colours were the most common in both sexes. The hens commonly had small round earlobes with varying colours, while cocks had large oval-shaped, mainly red (70%) earlobes. The single-comb type was dominant in both sexes, with wattles almost universally present. Frizzle and polydactyl allele frequencies were significantly lower (p < 0.05) than the expected Mendelian proportions, indicating a possible state of endangerment. Meanwhile, the estimated allele frequencies of ptilopody, tufted-crest, and rose comb alleles in the population were similar (p > 0.05) to the expected Mendelian frequencies. However, these strains did not show any significant (p > 0.05) influence on the body weight or the linear morphometric estimates except for being marginally higher than the normal strains. The phenotypic correlations of body weight and morphometric traits ranged from 0.457 to 0.668 and 0.292 to 0.454 in cocks and hens, respectively. These findings provide hints about the prospects for improved performance with modifications in the production environment. The wide phenotypic diversity would support management efforts for their sustainable utilisation and preservation.
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Affiliation(s)
- Illyass Yussif
- College of Agricultural and Environmental Sciences, Makerere University, Kampala, Uganda,*Correspondence: Illyass Yussif,
| | - Donald Rugira Kugonza
- College of Agricultural and Environmental Sciences, Makerere University, Kampala, Uganda
| | | | | | | | - Filomena Dos Anjos
- Faculty of Veterinary Medicine, Eduardo Mondlane University, Maputo, Mozambique
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Sugianto N, Newman C, Macdonald D, Buesching C. Extrinsic factors affecting cub development contribute to sexual size dimorphism in the European badger (Meles meles). ZOOLOGY 2019; 135:125688. [DOI: 10.1016/j.zool.2019.04.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2018] [Revised: 04/27/2019] [Accepted: 04/29/2019] [Indexed: 11/24/2022]
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Kappeler PM, Nunn CL, Vining AQ, Goodman SM. Evolutionary dynamics of sexual size dimorphism in non-volant mammals following their independent colonization of Madagascar. Sci Rep 2019; 9:1454. [PMID: 30723219 PMCID: PMC6363729 DOI: 10.1038/s41598-018-36246-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Accepted: 11/15/2018] [Indexed: 01/16/2023] Open
Abstract
As predicted by sexual selection theory, males are larger than females in most polygynous mammals, but recent studies found that ecology and life history traits also affect sexual size dimorphism (SSD) through evolutionary changes in either male size, female size, or both. The primates of Madagascar (Lemuriformes) represent the largest group of mammals without male-biased SSD. The eco-evo-devo hypothesis posited that adaptations to unusual climatic unpredictability on Madagascar have ultimately reduced SSD in lemurs after dispersing to Madagascar, but data have not been available for comparative tests of the corresponding predictions that SSD is also absent in other terrestrial Malagasy mammals and that patterns of SSD changed following the colonization of Madagascar. We used phylogenetic methods and new body mass data to test these predictions among the four endemic radiations of Malagasy primates, carnivorans, tenrecs, and rodents. In support of our prediction, we found that male-biased SSD is generally absent among all Malagasy mammals. Phylogenetic comparative analyses further indicated that after their independent colonization of Madagascar, SSD decreased in primates and tenrecs, but not in the other lineages or when analyzed across all species. We discuss several mechanisms that may have generated these patterns and conclude that neither the eco-evo-devo hypothesis, founder effects, the island rule nor sexual selection theory alone can provide a compelling explanation for the observed patterns of SSD in Malagasy mammals.
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Affiliation(s)
- Peter M Kappeler
- Wissenschaftskolleg zu Berlin, Berlin, Germany.
- Behavioral Ecology and Sociobiology Unit, German Primate Center - Leibniz Institute of Primatology, Göttingen, Germany.
- Department Sociobiology/Anthropology, University of Göttingen, Göttingen, Germany.
| | - Charles L Nunn
- Department of Evolutionary Anthropology, Duke University, Durham, NC, USA
- Duke Global Health Institute, Duke University, Durham, NC, USA
| | - Alexander Q Vining
- Department of Evolutionary Anthropology, Duke University, Durham, NC, USA
| | - Steven M Goodman
- Field Museum of Natural History, Chicago, IL, USA
- Association Vahatra, Antananarivo, Madagascar
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Fernandes Martins MJ, Hunt G, Lockwood R, Swaddle JP, Horne DJ. Correlation between investment in sexual traits and valve sexual dimorphism in Cyprideis species (Ostracoda). PLoS One 2017; 12:e0177791. [PMID: 28678866 PMCID: PMC5497955 DOI: 10.1371/journal.pone.0177791] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Accepted: 05/03/2017] [Indexed: 11/19/2022] Open
Abstract
Assessing the long-term macroevolutionary consequences of sexual selection has been hampered by the difficulty of studying this process in the fossil record. Cytheroid ostracodes offer an excellent system to explore sexual selection in the fossil record because their readily fossilized carapaces are sexually dimorphic. Specifically, males are relatively more elongate than females in this superfamily. This sexual shape difference is thought to arise so that males carapaces can accommodate their very large copulatory apparatus, which can account for up to one-third of body volume. Here we test this widely held explanation for sexual dimorphism in cytheroid ostracodes by correlating investment in male genitalia, a trait in which sexual selection is seen as the main evolutionary driver, with sexual dimorphism of carapace in the genus Cyprideis. We analyzed specimens collected in the field (C. salebrosa, USA; C. torosa, UK) and from collections of the National Museum of Natural History, Washington, DC (C. mexicana). We digitized valve outlines in lateral view to obtain measures of size (valve area) and shape (elongation, measured as length to height ratio), and obtained several dimensions from two components of the hemipenis: the muscular basal capsule, which functions as a sperm pump, and the section that includes the intromittent organ (terminal extension). In addition to the assessment of this primary sexual trait, we also quantified two dimensions of the male secondary sexual trait—where the transformed right walking leg functions as a clasping organ during mating. We also measured linear dimensions from four limbs as indicators of overall (soft-part) body size, and assessed allometry of the soft anatomy. We observed significant correlations in males between valve size, but not elongation, and distinct structural parts of the hemipenis, even after accounting for their shared correlation with overall body size. We also found weak but significant positive correlation between valve elongation and the degree of sexual dimorphism of the walking leg, but only in C. torosa. The correlation between the hemipenis parts, especially basal capsule size and male valve size dimorphism suggests that sexual selection on sperm size, quantity, and/or efficiency of transfer may drive sexual size dimorphism in these species, although we cannot exclude other aspects of sexual and natural selection.
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Affiliation(s)
- Maria João Fernandes Martins
- Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington DC, United States of America
- * E-mail:
| | - Gene Hunt
- Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington DC, United States of America
| | - Rowan Lockwood
- Department of Geology, College of William and Mary, Williamsburg, Virginia, United States of America
| | - John P. Swaddle
- Department of Biology, College of William and Mary, Williamsburg, Virginia, United States of America
| | - David J. Horne
- School of Geography, Queen Mary University of London, London, United Kingdom
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Joos J, Kirchner M, Vamberger M, Kaviani M, Rahimibashar MR, Fritz U, MÜller J. Climate and patterns of body size variation in the European pond turtle, Emys orbicularis. Biol J Linn Soc Lond 2017. [DOI: 10.1093/biolinnean/blx056] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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Mori E, Iacucci A, Castiglia R, Santini L. Sexual-size dimorphism in two synanthropic rat species: Comparison and eco-evolutionary perspectives. Mamm Biol 2017. [DOI: 10.1016/j.mambio.2016.12.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Čanády A, Mošanský L, Krišovský P. Sexual size monomorphism and body variation in the fat dormouse Glis glis in Slovakia. Biologia (Bratisl) 2016. [DOI: 10.1515/biolog-2016-0123] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Manicom C, Alford R, Schoener TW, Schwarzkopf L. Mechanisms causing variation in sexual size dimorphism in three sympatric, congeneric lizards. Ecology 2014; 95:1531-44. [DOI: 10.1890/13-0693.1] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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French JA, Mustoe AC, Cavanaugh J, Birnie AK. The influence of androgenic steroid hormones on female aggression in 'atypical' mammals. Philos Trans R Soc Lond B Biol Sci 2013; 368:20130084. [PMID: 24167314 PMCID: PMC3826213 DOI: 10.1098/rstb.2013.0084] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Dimorphism on dominance and agonistic behaviour in mammals tends to be strongly biased toward males. In this review, we focus on a select few species of mammals in which females are as or more aggressive than males, and/or are dominant to males, and explore the role of androgenic hormones in mediating this important difference. While the data are not as clear-cut as those published on traditional laboratory mammals, our review highlights important endocrine substrates for both organizational and activational influences of steroids on female aggressive behaviour. We highlight areas in which further observations and experiments are crucial, especially the potential facilitative effects of androgens on female aggression. Finally, new and innovative techniques, including molecular genetics and receptor pharmacology, portend important insights into the ways in which androgenic hormones regulate aggressive behaviour in 'atypical' female mammals.
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Affiliation(s)
- Jeffrey A. French
- Department of Psychology, Callitrichid Research Center, University of Nebraska at Omaha, Omaha, NE 68182, USA
- Department of Biology, University of Nebraska at Omaha, Omaha, NE 68182, USA
| | - Aaryn C. Mustoe
- Department of Psychology, Callitrichid Research Center, University of Nebraska at Omaha, Omaha, NE 68182, USA
| | - Jon Cavanaugh
- Department of Psychology, Callitrichid Research Center, University of Nebraska at Omaha, Omaha, NE 68182, USA
| | - Andrew K. Birnie
- Department of Psychology, Callitrichid Research Center, University of Nebraska at Omaha, Omaha, NE 68182, USA
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Ecological Selection and the Evolution of Body Size and Sexual Size Dimorphism in the Galapagos Flightless Cormorant. SOCIAL AND ECOLOGICAL INTERACTIONS IN THE GALAPAGOS ISLANDS 2013. [DOI: 10.1007/978-1-4614-6732-8_12] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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NICOLAS VIOLAINE, AKPATOU BERTIN, WENDELEN WIM, KERBIS PETERHANS JULIAN, OLAYEMI AYODEJI, DECHER JAN, MISSOUP ALAINDIDIER, DENYS CHRISTIANE, BARRIERE PATRICK, CRUAUD CORINNE, COLYN MARC. Molecular and morphometric variation in two sibling species of the genus Praomys (Rodentia: Muridae): implications for biogeography. Zool J Linn Soc 2010. [DOI: 10.1111/j.1096-3642.2009.00602.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Zysling DA, Greives TJ, Breuner CW, Casto JM, Demas GE, Ketterson ED. Behavioral and physiological responses to experimentally elevated testosterone in female dark-eyed juncos (Junco hyemalis carolinensis). Horm Behav 2006; 50:200-7. [PMID: 16678179 DOI: 10.1016/j.yhbeh.2006.03.004] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2005] [Revised: 02/28/2006] [Accepted: 03/03/2006] [Indexed: 10/24/2022]
Abstract
Testosterone mediates the expression of many fitness-related traits in male vertebrates and is thought to account for numerous sex differences in trait expression. Testosterone is also secreted by females; however, far less is known regarding its effects on female physiology and behavior. Using a bird species in which the effects of testosterone on males are well characterized, the dark-eyed junco (Junco hyemalis), we tested whether an increase in exogenous testosterone in females would alter the phenotypic expression of a suite of behavioral and physiological traits. We found that increased testosterone levels in female dark-eyed juncos led to decreased cell-mediated immune function and increased intrasexual aggression, hypothalamo-pituitary-adrenal (HPA) axis responsiveness, baseline corticosterone and corticosterone-binding globulin (CBG) levels. Furthermore, immunosuppression following testosterone implantation was negatively correlated with total and free testosterone but did not appear to be related to either total or free corticosterone. These results demonstrate that the phenotypic impact of elevated testosterone is not confined to males in dark-eyed juncos, and that the impact in adults can be similar in males and females. We discuss these results in the context of potential endocrine-immune interactions and the evolution of sexual dimorphism.
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Affiliation(s)
- Devin A Zysling
- Department of Biology, Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA.
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Johnson JB, McBrayer LD, Saenz D. ALLOMETRY, SEXUAL SIZE DIMORPHISM, AND NICHE PARTITIONING IN THE MEDITERRANEAN GECKO (HEMIDACTYLUS TURCICUS). SOUTHWEST NAT 2005. [DOI: 10.1894/0038-4909(2005)050[0435:assdan]2.0.co;2] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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17
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Ketterson ED, Nolan V, Sandell M. Testosterone in Females: Mediator of Adaptive Traits, Constraint on Sexual Dimorphism, or Both? Am Nat 2005; 166 Suppl 4:S85-98. [PMID: 16224714 DOI: 10.1086/444602] [Citation(s) in RCA: 187] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
When selection on males and females differs, the sexes may diverge in phenotype. Hormones serve as a proximate regulator of sex differences by mediating sex-biased trait expression. To integrate these perspectives, we consider how suites of traits mediated by the same hormone in both sexes might respond to selection. In male birds, plasma testosterone (T) varies seasonally and among species according to mating system. When elevated experimentally, it is known to enhance some components of fitness and to decrease others. We report that female T also varies seasonally and co-varies with male T. Female T is higher in relation to male T in sexually monomorphic species and is higher absolutely in females of species with socially monogamous mating systems, which suggests adaptation. We also consider the effect of experimentally elevated T on females and whether traits are sensitive to altered T. We hypothesize that sensitive traits could become subject to selection after a natural change in T and that traits with opposing fitness consequences in males and females could constrain dimorphism. Results from birds, including the dark-eyed junco (Junco hyemalis), reveal many sensitive traits, some of which appear costly and may help to account for observed levels of sexual dimorphism.
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Affiliation(s)
- E D Ketterson
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, Indiana 47405, USA.
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SCHÄUBLE CHLOES. Variation in body size and sexual dimorphism across geographical and environmental space in the frogs Limnodynastes tasmaniensis and L. peronii. Biol J Linn Soc Lond 2004. [DOI: 10.1111/j.1095-8312.2004.00315.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Lindenfors P, Székely T, Reynolds JD. Directional changes in sexual size dimorphism in shorebirds, gulls and alcids. J Evol Biol 2003; 16:930-8. [PMID: 14635908 DOI: 10.1046/j.1420-9101.2003.00595.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The Charadrii (shorebirds, gulls and alcids) are one of the most diverse avian groups from the point of view of sexual size dimorphism, exhibiting extremes in both male-biased and female-biased dimorphism, as well as monomorphism. In this study we use phylogenetic comparative analyses to investigate how size dimorphism has changed over evolutionary time, distinguishing between changes that have occurred in females and in males. Independent contrasts analyses show that both body mass and wing length have been more variable in males than in females. Directional analyses show that male-biased dimorphism has increased after inferred transitions towards more polygynous mating systems. There have been analogous increases in female-biased dimorphism after transitions towards more socially polyandrous mating systems. Changes in dimorphism in both directions are attributable to male body size changing more than female body size. We suggest that this might be because females are under stronger natural selection constraints related to fecundity. Taken together, our results suggest that the observed variation in dimorphism of Charadrii can be best explained by male body size responding more sensitively to variable sexual selection than female body size.
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Affiliation(s)
- P Lindenfors
- Department of Zoology, Stockholm University, Stockholm, Sweden.
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Schulte-Hostedde AI, Millar JS, Gibbs HL. Female-biased sexual size dimorphism in the yellow-pine chipmunk (Tamias amoenus): sex-specific patterns of annual reproductive success and survival. Evolution 2002; 56:2519-29. [PMID: 12583591 DOI: 10.1111/j.0014-3820.2002.tb00176.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Sexual size dimorphism is ultimately the result of independent, sex-specific selection on body size. In mammals, male-biased sexual size dimorphism is the predominant pattern, and it is usually attributed to the polygynous mating system prevalent in most mammals. This sole explanation is unsatisfying because selection acts on both sexes simultaneously, therefore any explanation of sexual size dimorphism should explain why one sex is relatively large and the other is small. Using mark-recapture techniques and DNA microsatellite loci to assign parentage, we examined sex-specific patterns of annual reproductive success and survival in the yellow-pine chipmunk (Tamias amoenus), a small mammal with female-biased sexual size dimorphism, to test the hypothesis that the dimorphism was related to sex differences in the relationship between body size and fitness. Chipmunks were monitored and body size components measured over three years in the Kananaskis Valley, Alberta, Canada. Male reproductive success was independent of body size perhaps due to trade-offs in body size associated with behavioral components of male mating success: dominance and running speed. Male survival was consistent with stabilizing selection for overall body size and body size components. The relationship between reproductive success and female body size fluctuated. In two of three years the relationship was positive, whereas in one year the relationship was negative. This may have been the result of differences in environmental conditions among years. Large females require more energy to maintain their soma than small females and may be unable to maintain lactation in the face of challenging environmental conditions. Female survival was positively related to body size, with little evidence for stabilizing selection. Sex differences in the relationship between body size and fitness (reproductive success and survival) were the result of different processes, but were ultimately consistent with female-biased sexual size dimorphism evident in this species.
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Affiliation(s)
- Albrecht I Schulte-Hostedde
- Ecology and Evolution Group, Department of Zoology, University of Western Ontario, London, Ontario K7L 3N6, Canada.
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Swaddle JP, Reierson GW. Testosterone increases perceived dominance but not attractiveness in human males. Proc Biol Sci 2002; 269:2285-9. [PMID: 12495494 PMCID: PMC1691166 DOI: 10.1098/rspb.2002.2165] [Citation(s) in RCA: 135] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Recent evidence suggests that certain features on the human face indicate hormonal levels during growth, and that women judge the attractiveness of potential partners based on the appearance of these features. One entrenched notion is male facial features that are affected by testosterone are used as direct cues in mate preference. Testosterone may be particularly revealing as it is purported to be an honest indicator of male fitness. Increased testosterone may impose an immunocompetence handicap on the bearer and only the best males can carry this handicap. To date, tests of this theory have been indirect, and have relied on digital manipulations that represent unrealistic continuums of masculine and feminine faces. We provide a much more direct test by manipulating digitally male faces to mimic known shape variation, caused by varying levels of testosterone through puberty. We produced a continuum of faces that ranged from low to high levels of testosterone in male faces and asked women to choose the points on the continuum that appeared most attractive and most physically dominant. Our data indicate that high testosterone faces reveal dominance. However, there is no evidence of directional selection for increased (or decreased) testosterone in terms of attractiveness to the opposite sex. We discuss the relevance and applicability of evolutionary interpretations of our data and, contrary to predictions, provide evidence of stabilizing selection acting on testosterone through mate preferences.
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Affiliation(s)
- John P Swaddle
- Biology Department, College of William & Mary, Williamsburg, VA 23197, USA.
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Wood W, Eagly AH. A cross-cultural analysis of the behavior of women and men: implications for the origins of sex differences. Psychol Bull 2002; 128:699-727. [PMID: 12206191 DOI: 10.1037/0033-2909.128.5.699] [Citation(s) in RCA: 482] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
This article evaluates theories of the origins of sex differences in human behavior. It reviews the cross-cultural evidence on the behavior of women and men in nonindustrial societies, especially the activities that contribute to the sex-typed division of labor and patriarchy. To explain the cross-cultural findings, the authors consider social constructionism, evolutionary psychology, and their own biosocial theory. Supporting the biosocial analysis, sex differences derive from the interaction between the physical specialization of the sexes, especially female reproductive capacity, and the economic and social structural aspects of societies. This biosocial approach treats the psychological attributes of women and men as emergent given the evolved characteristics of the sexes, their developmental experiences, and their situated activity in society.
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Affiliation(s)
- Wendy Wood
- Department of Psychology, Texas A&M University, College Station 77843, USA.
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Schulte-Hostedde AI, Millar JS, Gibbs HL. FEMALE-BIASED SEXUAL SIZE DIMORPHISM IN THE YELLOW-PINE CHIPMUNK (TAMIAS AMOENUS): SEX-SPECIFIC PATTERNS OF ANNUAL REPRODUCTIVE SUCCESS AND SURVIVAL. Evolution 2002. [DOI: 10.1554/0014-3820(2002)056[2519:fbssdi]2.0.co;2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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