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Carsia RV, McIlroy PJ, John-Alder HB. Invited review: Adrenocortical function in avian and non-avian reptiles: Insights from dispersed adrenocortical cells. Comp Biochem Physiol A Mol Integr Physiol 2023; 281:111424. [PMID: 37080352 DOI: 10.1016/j.cbpa.2023.111424] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Revised: 04/07/2023] [Accepted: 04/08/2023] [Indexed: 04/22/2023]
Abstract
Herein we review our work involving dispersed adrenocortical cells from several lizard species: the Eastern Fence Lizard (Sceloporus undulatus), Yarrow's Spiny Lizard (Sceloporus jarrovii), Striped Plateau Lizard (Sceloporus virgatus) and the Yucatán Banded Gecko (Coleonyx elegans). Early work demonstrated changes in steroidogenic function of adrenocortical cells derived from adult S. undulatus associated with seasonal interactions with sex. However, new information suggests that both sexes operate within the same steroidogenic budget over season. The observed sex effect was further explored in orchiectomized and ovariectomized lizards, some supported with exogenous testosterone. Overall, a suppressive effect of testosterone was evident, especially in cells from C. elegans. Life stage added to this complex picture of adrenal steroidogenic function. This was evident when sexually mature and immature Sceloporus lizards were subjected to a nutritional stressor, cricket restriction/deprivation. There were divergent patterns of corticosterone, aldosterone, and progesterone responses and associated sensitivities of each to corticotropin (ACTH). Finally, we provide strong evidence that there are multiple, labile subpopulations of adrenocortical cells. We conclude that the rapid (days) remodeling of adrenocortical steroidogenic function through fluctuating cell subpopulations drives the circulating corticosteroid profile of Sceloporus lizard species. Interestingly, progesterone and aldosterone may be more important with corticosterone serving as essential supportive background. In the wild, the flux in adrenocortical cell subpopulations may be adversely susceptible to climate-change related disruptions in food sources and to xenobiotic/endocrine-disrupting chemicals. We urge further studies using native lizard species as bioindicators of local pollutants and as models to examine the broader eco-exposome.
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Affiliation(s)
- Rocco V Carsia
- Department of Cell Biology and Neuroscience, Rowan University School of Osteopathic Medicine, 2 Medical Center Drive, Stratford, NJ 08084, United States.
| | - Patrick J McIlroy
- Department of Biology and Center for Computational and Integrative Biology, Rutgers University, 311 North Fifth Street, Camden, NJ 08102, United States
| | - Henry B John-Alder
- Department of Ecology, Evolution, and Natural Resources, The Pinelands Field Station Rutgers University, 14 College Farm Road, New Brunswick, NJ 08901, United States
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Alward BA, Hoadley AP, Jackson LR, Lopez MS. Genetic dissection of steroid-hormone modulated social behavior: Novel paralogous genes are a boon for discovery. Horm Behav 2023; 147:105295. [PMID: 36502603 PMCID: PMC9839648 DOI: 10.1016/j.yhbeh.2022.105295] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Revised: 11/23/2022] [Accepted: 12/01/2022] [Indexed: 12/13/2022]
Abstract
Research across species has led to important discoveries on the functions of steroid hormones in the regulation of behavior. However, like in many fields, advancements in transgenic and mutagenic technology allowed mice to become the premier genetic model for conducting many experiments to understand how steroids control social behavior. Since there has been a general lack of parallel methodological developments in other species, many of the findings cannot be generalized. This is especially the case for teleost fish, in which a whole-genome duplication produced novel paralogs for key steroid hormone signaling genes. In this review, we summarize technical advancements over the history of the field of neuroendocrinology that have led to important insights in our understanding of the control of social behavior by steroids. We demonstrate that early mouse genetic models to understand these mechanisms suffered from several issues that were remedied by more precise transgenic technological advancements. We then highlight the importance of CRISPR/Cas9 gene editing tools that will in time bridge the gap between mice and non-traditional model species for understanding principles of steroid hormone action in the modulation of social behavior. We specifically highlight the role of teleost fish in bridging this gap because they are 1) highly genetically tractable and 2) provide a novel advantage in achieving precise genetic control. The field of neuroendocrinology is entering a new "gene editing revolution" that will lead to novel discoveries about the roles of steroid hormones in the regulation and evolutionary trajectories of social behavior.
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Affiliation(s)
- Beau A Alward
- University of Houston, Department of Psychology, United States of America; University of Houston, Department of Biology and Biochemistry, United States of America.
| | - Andrew P Hoadley
- University of Houston, Department of Psychology, United States of America
| | - Lillian R Jackson
- University of Houston, Department of Psychology, United States of America
| | - Mariana S Lopez
- University of Houston, Department of Psychology, United States of America
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3
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Critical Thermal Capacities of Hyla chrysoscelis in Relation to Season. J HERPETOL 2020. [DOI: 10.1670/19-124] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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4
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Tarkhnishvili D, Barateli N, Murtskhvaladze M, Iankoshvili G. Estimating phenotypic heritability of sexual and unisexually reproducing rock lizards (genus Darevskia). ZOOL ANZ 2020. [DOI: 10.1016/j.jcz.2020.02.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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5
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Critical thermal tolerance of invasion: Comparative niche breadth of two invasive lizards. J Therm Biol 2019; 86:102432. [PMID: 31789228 DOI: 10.1016/j.jtherbio.2019.102432] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Revised: 09/09/2019] [Accepted: 10/04/2019] [Indexed: 11/21/2022]
Abstract
Understanding the evolution of thermal tolerance in ectotherms is particularly important given the current period of rapid change in the environment and thermal climate. Specifically, introduced species have the potential to evolve different thermal tolerances than native populations due to rapid evolution and novel selection pressures. Our study examined critical thermal tolerance in two introduced lizard species, the European wall lizard (Podarcis muralis) in Ohio and Kentucky, and the Mediterranean gecko (Hemidactylus turcicus) from Texas through Alabama. We tested the hypotheses that critical thermal maximum, minimum, and breadth varies among introduced populations of P. muralis and H. turcicus, and that critical thermal tolerance broadens when moving away from the introduction site, because dispersal across novel environments may remove dispersers with narrow thermal tolerances. We found that among P. muralis populations, CTmin and thermal breadth were significantly different. Specifically, when moving away from the introduction site, lizards exhibited increased cold tolerance and broader thermal breadth. Variability in thermal parameters were also lowest at the site closest to the introduction point in P. muralis. In contrast, H. turcicus had no significant differences in critical thermal minimum, maximum, or breadth among sites, or with respect to distance from introduction point. However, we did find little variability in thermal maximum, compared to greater variability in overall tolerance and critical thermal minimums. Thus, this study shows that selection on thermal tolerance and dispersal characteristics occur in novel climatic environments. Understanding how thermal tolerance changes over time can aid in predicting establishment and movement of introduced species, with applications for native species during a time of global climatic change.
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6
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Agha M, Ennen JR, Nowakowski AJ, Lovich JE, Sweat SC, Todd BD. Macroecological patterns of sexual size dimorphism in turtles of the world. J Evol Biol 2018; 31:336-345. [DOI: 10.1111/jeb.13223] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Accepted: 12/06/2017] [Indexed: 11/30/2022]
Affiliation(s)
- M. Agha
- Department of Wildlife, Fish, and Conservation Biology; University of California, Davis; Davis CA USA
| | - J. R. Ennen
- Tennessee Aquarium Conservation Institute; Chattanooga TN USA
| | - A. J. Nowakowski
- Department of Wildlife, Fish, and Conservation Biology; University of California, Davis; Davis CA USA
| | - J. E. Lovich
- Southwest Biological Science Center; U.S. Geological Survey; Flagstaff AZ USA
| | - S. C. Sweat
- Tennessee Aquarium Conservation Institute; Chattanooga TN USA
| | - B. D. Todd
- Department of Wildlife, Fish, and Conservation Biology; University of California, Davis; Davis CA USA
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Silva FMD, Oliveira LSD, Nascimento LRDS, Machado FA, Prudente ALDC. Sexual dimorphism and ontogenetic changes of Amazonian pit vipers (Bothrops atrox). ZOOL ANZ 2017. [DOI: 10.1016/j.jcz.2017.11.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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8
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Pollock NB, Feigin S, Drazenovic M, John-Alder HB. Sex hormones and the development of sexual size dimorphism: 5α-dihydrotestosterone inhibits growth in a female-larger lizard ( Sceloporus undulatus). ACTA ACUST UNITED AC 2017; 220:4068-4077. [PMID: 28912255 DOI: 10.1242/jeb.166553] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Accepted: 09/11/2017] [Indexed: 12/18/2022]
Abstract
Sexual differences in adult body size [sexual size dimorphism (SSD)] and color (sexual dichromatism) are widespread, and both male- and female-biased dimorphisms are observed even among closely related species. A growing body of evidence indicates testosterone can regulate growth, thus the development of SSD, and sexual dichromatism. However, the mechanism(s) underlying these effects are conjectural, including possible conversions of testosterone to estradiol (E2) or 5α-dihydrotestosterone (DHT). In the present study, we hypothesized that the effects of testosterone are physiological responses mediated by androgen receptors, and we tested two specific predictions: (1) that DHT would mimic the effects of testosterone by inhibiting growth and enhancing coloration, and (2) that removal of endogenous testosterone via surgical castration would stimulate growth. We also hypothesized that females share downstream regulatory networks with males and predicted that females and males would respond similarly to DHT. We conducted experiments on eastern fence lizards (Sceloporus undulatus), a female-larger species with striking sexual dichromatism. We implanted Silastic® tubules containing 150 µg DHT into intact females and intact and castrated males. We measured linear growth rates and quantified color for ventral and dorsal surfaces. We found that DHT decreased growth rate and enhanced male-typical coloration in both males and females. We also found that, given adequate time, castration alone is sufficient to stimulate growth rate in males. The results presented here suggest that: (1) the effects of testosterone on growth and coloration are mediated by androgen receptors without requiring aromatization of testosterone into E2, and (2) females possess the androgen-receptor-mediated regulatory networks required for initiating male-typical inhibition of growth and enhanced coloration in response to androgens.
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Affiliation(s)
- Nicholas B Pollock
- Graduate Program in Ecology and Evolution, Rutgers University, New Brunswick, NJ 08901, USA
| | - Stephanie Feigin
- Department of Ecology, Evolution, and Natural Resources, Rutgers University, New Brunswick, NJ 08901, USA
| | - Marko Drazenovic
- Department of Ecology, Evolution, and Natural Resources, Rutgers University, New Brunswick, NJ 08901, USA
| | - Henry B John-Alder
- Graduate Program in Ecology and Evolution, Rutgers University, New Brunswick, NJ 08901, USA.,Department of Ecology, Evolution, and Natural Resources, Rutgers University, New Brunswick, NJ 08901, USA
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Kubička L, Starostová Z, Kratochvíl L. Endogenous control of sexual size dimorphism: Gonadal androgens have neither direct nor indirect effect on male growth in a Madagascar ground gecko (Paroedura picta). Gen Comp Endocrinol 2015; 224:273-7. [PMID: 26431613 DOI: 10.1016/j.ygcen.2015.09.028] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Revised: 09/07/2015] [Accepted: 09/26/2015] [Indexed: 10/23/2022]
Abstract
Changes in the effect of gonadal androgens on male growth are considered as a possible mechanism allowing shifts in magnitude and even direction of sexual size dimorphism in vertebrates, particularly squamate reptiles. Positive effects of gonadal androgens on male growth were found in several male-larger species of lizards. Contrastingly, we document that in the male-larger Madagascar ground gecko (Paroedura picta) gonadal androgens do not affect male growth under constant thermal conditions. However, the absence of a thermal gradient might prevent the potential indirect effect of gonadal androgens on growth via the influence of circulating hormones on an individual's thermoregulation and hence metabolic rate. In order to study this, we monitored the growth and body temperature of socially isolated sham-operated and castrated males of the same species in a thermal gradient. We also compared the oxygen consumption and activity between the treatment groups in the open field to test the effect of gonadal hormones on these traits potentially affecting growth. Even under a thermal gradient we found no effect of gonadal androgens on growth rate or final body dimensions. Castration also did not significantly affect oxygen consumption or activity in the open field test. Together with our previous findings, we can exclude both the direct effect of male gonadal androgens on the ontogeny of sexual size dimorphism via the influence on the growth axis, and the indirect influence of gonadal androgens acting on the ontogeny of SSD through the effect on thermoregulation, metabolic rate and activity.
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Affiliation(s)
- Lukáš Kubička
- Faculty of Science, Charles University in Prague, Department of Ecology, Viničná 7, 128 44 Praha 2, Czech Republic.
| | - Zuzana Starostová
- Faculty of Science, Charles University in Prague, Department of Zoology, Viničná 7, 128 44 Praha 2, Czech Republic
| | - Lukáš Kratochvíl
- Faculty of Science, Charles University in Prague, Department of Ecology, Viničná 7, 128 44 Praha 2, Czech Republic
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Zhao W, Liu NF. The proximate causes of sexual size dimorphism in Phrynocephalus przewalskii. PLoS One 2014; 9:e85963. [PMID: 24465815 PMCID: PMC3897606 DOI: 10.1371/journal.pone.0085963] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Accepted: 12/03/2013] [Indexed: 11/19/2022] Open
Abstract
Sexual size dimorphism (SSD) is a common phenomenon and is a central topic in evolutionary biology. Recently, the importance of pursuing an ontogenetic perspective of SSD has been emphasized, to elucidate the proximate physiological mechanisms leading to its evolution. However, such research has seldom focused on the critical periods when males and females diverge. Using mark-recapture data, we investigated the development of SSD, sex-specific survivorship, and growth rates in Phrynocephalus przewalskii (Agamidae). We demonstrated that both male and female lizards are reproductively mature at age 10-11 months (including 5 months hibernation). Male-biased SSD in snout-vent length (SVL) was only found in adults and was fully expressed at age 11 months (June of the first full season of activity), just after sexual maturation. However, male-biased SSD in tail length (TL), hind-limb length (LL), and head width (HW) were fully expressed at age 9-10 months, just before sexual maturation. Analysis of age-specific linear growth rates identified sexually dimorphic growth during the fifth growth month (age 10-11 months) as the proximate cause of SSD in SVL. The males experienced higher mortality than females in the first 2 years and only survived better than females after SSD was well developed. This suggests that the critical period of divergence in the sizes of male and female P. przewalskii occurs between 10 and 11 months of age (May to June during the first full season of activity), and that the sexual difference in growth during this period is the proximate cause. However, the sexual difference in survivorship cannot explain the male-biased SSD in SVL. Our results indicate that performance-related characteristics, such as TL, HW, and LL diverged earlier than SVL. The physiological mechanisms underlying the different growth patterns of males and females may reflect different energy allocations associated with their different reproductive statuses.
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Affiliation(s)
- Wei Zhao
- School of Life Sciences, Lanzhou University, Lanzhou, China
| | - Nai-fa Liu
- School of Life Sciences, Lanzhou University, Lanzhou, China
- * E-mail:
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Ramírez-Bautista A, Smith GR, Leyte-Manrique A, Hernández-Salinas U. No Sexual Size-Dimorphism In the Eastern Spiny Lizard,Sceloporus spinosus, from Guadalcázar, San Luis Potosi, Mexico. SOUTHWEST NAT 2013. [DOI: 10.1894/0038-4909-58.4.505] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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12
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Divergent Sex-Specific Plasticity in Long-Lived Vertebrates with Contrasting Sexual Dimorphism. Evol Biol 2013. [DOI: 10.1007/s11692-013-9249-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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13
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Kubička L, Golinski A, John-Alder H, Kratochvíl L. Ontogeny of pronounced female-biased sexual size dimorphism in the Malaysian cat gecko (Aeluroscalabotes felinus: Squamata: Eublepharidae): a test of the role of testosterone in growth regulation. Gen Comp Endocrinol 2013; 188:183-8. [PMID: 23545460 DOI: 10.1016/j.ygcen.2013.03.016] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Revised: 03/11/2013] [Accepted: 03/12/2013] [Indexed: 12/15/2022]
Abstract
Species differences in the effect of male gonadal androgens on male growth are considered a possible mechanism allowing shifts in magnitude and even direction of sexual size dimorphism (SSD) in squamate reptiles. According to the bipotential growth regulation hypothesis, the androgen testosterone (T) enhances male growth in species with male-biased SSD and conversely inhibits male growth in males of female-larger species. In the present study, we describe the ontogeny of the pronounced female-biased SSD and report the effect of T on growth via hormonal manipulations in males and females of the Malaysian cat gecko (Aeluroscalabotes felinus). In accord with the predictions of the bipotential growth regulation hypothesis, growth was inhibited by replacement of T in castrated males. Additionally, exogenous T inhibited growth of females to male-typical levels. Nevertheless, male castration alone did not significantly affect growth, contrary to the prediction of the bipotential growth regulation hypothesis, which contradicts the generality of this hypothesis. Application of exogenous T to females can interfere with normal ovarian function. Therefore, although not directly tested in this study, we suggest that ovarian effects on the ontogeny of SSD in A. felinus are consistent with our results. The development of SSD is a function of differential growth between the sexes, and potential sex-specific growth regulation in both males and females should be taken into account as possible proximate mechanisms responsible for SSD.
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Affiliation(s)
- Lukáš Kubička
- Faculty of Science, Charles University in Prague, Department of Ecology, Viničná 7, 128 44 Praha 2, Czech Republic.
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14
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Starostová Z, Kubička L, Golinski A, Kratochvil L. Neither male gonadal androgens nor female reproductive costs drive development of sexual size dimorphism in lizards. J Exp Biol 2013; 216:1872-80. [DOI: 10.1242/jeb.079442] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Summary
Sexual size dimorphism (SSD) is an extensively studied phenomenon in animals, including reptiles, but the proximate mechanism of its development is poorly understood. The most pervasive candidates are (1) androgen-mediated control of growth, i.e. positive effect of gonadal androgens (testosterone) on male growth in male-larger species, while negative in female-larger species; and (2) sex-specific differences in energy allocation to growth, e.g. sex with larger reproductive costs should reach smaller body size. We tested these hypotheses in adults of the male-larger lizard Paroedura picta by conducting castrations with and without testosterone implants in males and manipulating reproductive status in females. Castration or testosterone replacement had no significant effect on final body length in males. High investment to reproduction had no significant effect on final body length in intact females. Interestingly, ovariectomized females and females with testosterone implants grew to larger body size than intact females. We found support for neither of the above hypotheses and suggest that previously reported effects of gonadal androgens on growth in male lizards could be a consequence of altered behaviour or social status in manipulated individuals. Exogenous testosterone in females led to decreased size of ovaries, its effect on body size may be caused by interference with normal ovarian function. We suggest that ovarian factors, perhaps estrogens, not reproductive costs, can modify growth in female lizards and may thus contribute to the development of SSD. This hypothesis is largely supported by published results on effect of testosterone treatment or ovariectomy on body size in female squamates.
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15
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BONNET XAVIER, LORIOUX SOPHIE, PEARSON DAVID, AUBRET FABIEN, BRADSHAW DON, DELMAS VIRGINIE, FAUVEL THOMAS. Which proximate factor determines sexual size dimorphism in tiger snakes? Biol J Linn Soc Lond 2011. [DOI: 10.1111/j.1095-8312.2011.01633.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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16
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The Role of Sex-specific Plasticity in Shaping Sexual Dimorphism in a Long-lived Vertebrate, the Snapping Turtle Chelydra serpentina. Evol Biol 2011. [DOI: 10.1007/s11692-011-9117-8] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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17
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Stahlschmidt ZR, Davis JR, DeNardo DF. Sexual variation in assimilation efficiency: its link to phenotype and potential role in sexual dimorphism. J Comp Physiol B 2010; 181:383-9. [DOI: 10.1007/s00360-010-0536-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2010] [Revised: 11/01/2010] [Accepted: 11/02/2010] [Indexed: 12/01/2022]
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18
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Cox RM, Parker EU, Cheney DM, Liebl AL, Martin LB, Calsbeek R. Experimental evidence for physiological costs underlying the trade-off between reproduction and survival. Funct Ecol 2010. [DOI: 10.1111/j.1365-2435.2010.01756.x] [Citation(s) in RCA: 118] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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19
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Bock BC, Zapata AM, Páez VP. Survivorship rates of adult Anolis mariarum (Squamata: Polychrotidae) in two populations with differing mean and asymptotic body sizes. PAPÉIS AVULSOS DE ZOOLOGIA 2010. [DOI: 10.1590/s0031-10492010000300001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
We compared adult survivorships in two populations of the lizard Anolis mariarum with different mean and asymptotic body sizes to examine one prediction of age-specific mortality theory; that populations that experience higher adult mortality should exhibit earlier maturation and smaller adult body sizes. We used a maximum likelihood approach to evaluate different survivorship models and model-averaging to estimate survivorship and capture probabilities for each site and sex. Relative tail length did not affect survivorship rates of adults in these two populations, but body size was related to survivorship, with the largest individuals at the time of first capture having lower survivorship rates, so body size was included as a covariate in some of the models examined. Analyses revealed that males at both sites had higher survivorships than females, but there were no differences among the sites in survivorship rates or capture probabilities for either sex. The differences in body sizes documented for these sites still could represent life history adaptations to differences among the sites in mortality rates in the egg or juvenile stages of the life cycle, or may represent a case of phenotypic plasticity to differing environmental conditions, but they appear not to be related to differences in adult survivorships. The estimates of annual survivorships (11.7% to 21.2%) were high for a small, mainland Anolis, and this is the first report of survivorships of male anoles exceeding those of females.
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Affiliation(s)
| | - Ana María Zapata
- Universidad Nacional de Colombia, Colombia; Corporación Autónoma Regional de Quindío, Colombia
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Cox R, Stenquist D, Henningsen J, Calsbeek R. Manipulating Testosterone to Assess Links between Behavior, Morphology, and Performance in the Brown Anole Anolis sagrei. Physiol Biochem Zool 2009; 82:686-98. [DOI: 10.1086/605391] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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21
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Cox RM, Calsbeek R. Sex-specific selection and intraspecific variation in sexual size dimorphism. Evolution 2009; 64:798-809. [PMID: 19796147 DOI: 10.1111/j.1558-5646.2009.00851.x] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Sexual size dimorphism (SSD) is thought to evolve due to sex differences in selection on body size, but it is largely unknown whether intraspecific variation in SSD reflects differences in sex-specific selection among populations. We addressed this question by comparing viability selection between two island populations of the brown anole lizard (Anolis sagrei) that differ in the magnitude of male-biased SSD. On both islands, females experienced stabilizing selection favoring intermediate size whereas males experienced directional selection favoring larger size. Thus, sex-specific selection matched the overall pattern of male-biased SSD, but population differences in the magnitude of SSD were not associated with local differences in selection. Rather, population differences in SSD appear to result from underlying differences in the environmental potential for a rapid growth, coupled with sex-specific phenotypic plasticity. Males grew more slowly on the island with low SSD whereas growth of females did not differ between islands. Both sexes had substantially lower mass per unit length on the island with low SSD, suggesting that they were in a relatively poorer energetic condition. We propose that this energetic constraint disproportionately impacts growth of males due to their greater absolute energy requirements, thus driving intraspecific variation in SSD.
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Affiliation(s)
- Robert M Cox
- Dartmouth College, Biological Sciences, 401 Gilman Hall, Hanover, New Hampshire 03755, USA.
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COX RM, STENQUIST DS, CALSBEEK R. Testosterone, growth and the evolution of sexual size dimorphism. J Evol Biol 2009; 22:1586-98. [PMID: 19549143 DOI: 10.1111/j.1420-9101.2009.01772.x] [Citation(s) in RCA: 109] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- R. M. COX
- Department of Biological Sciences, Dartmouth College, Hanover, NH, USA
| | - D. S. STENQUIST
- Department of Biological Sciences, Dartmouth College, Hanover, NH, USA
| | - R. CALSBEEK
- Department of Biological Sciences, Dartmouth College, Hanover, NH, USA
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Cox RM, Zilberman V, John-Alder HB. Testosterone stimulates the expression of a social color signal in Yarrow's Spiny Lizard, Sceloporus jarrovii. ACTA ACUST UNITED AC 2008; 309:505-14. [PMID: 18661470 DOI: 10.1002/jez.481] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The sex steroid testosterone has been shown to regulate the development of male-specific coloration in many organisms that exhibit sexual dichromatism, but the role of testosterone is less certain for species in which both sexes express bright coloration. Lizards in the genus Sceloporus possess bright blue patches on their throats and abdomens. These patches, which are used in social signaling, are often regulated by testosterone and are consequently expressed only in males of most species. However, Yarrow's Spiny Lizard (Sceloporus jarrovii, Cope 1875) exhibits a derived condition in which both sexes express bright blue ventral patches despite dramatic sexual differences in circulating testosterone levels throughout postnatal ontogeny. In this study, we used surgical castration and hormone replacement in juvenile males to test the hypothesis that testosterone stimulates the expression of blue ventral coloration in S. jarrovii. In two separate experiments conducted in captivity and the natural field environment, we found that surgical castration decreased the hue and saturation while increasing the brightness of blue throat and abdominal patches. Castration also decreased the amount of black pigment bordering the blue throat patch. Treatment of castrated males with exogenous testosterone restored all aspects of ventral coloration to values similar to those of intact control males. Early organizational effects of testosterone during prenatal development may lead to the expression of blue coloration in both sexes, but the results of our present experiments indicate that subsequent effects of testosterone during sexual maturation further enhance the coloration of males.
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Affiliation(s)
- Robert M Cox
- Graduate Program in Ecology and Evolution, Rutgers University, New Brunswick, New Jersey.
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Carsia RV, McIlroy PJ, Cox RM, Barrett M, John-Alder HB. Gonadal modulation of in vitro steroidogenic properties of dispersed adrenocortical cells from Sceloporus lizards. Gen Comp Endocrinol 2008; 158:202-10. [PMID: 18708060 DOI: 10.1016/j.ygcen.2008.07.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2008] [Revised: 06/23/2008] [Accepted: 07/17/2008] [Indexed: 11/28/2022]
Abstract
Effects of adrenal corticosteroids on reproductive and endocrine functions of the gonads are well known, but reciprocal effects of gonadal hormones on the hypothalamo-pituitary-adrenal (HPA) axis and on adrenocortical steroidogenesis in particular have received much less attention. We investigated effects of gonadectomy and testosterone (T) replacement on adrenocortical cell function in a year-long field study of male Sceloporus undulatus (Eastern Fence Lizard) and in a shorter term laboratory study with male Sceloporus jarrovii (Yarrow's Spiny Lizard). We also compared females to males in Sceloporus virgatus (Striped Plateau Lizard) and investigated effects of gonadectomy in short-term laboratory experiment on females of this species. As measured by in vitro production of progesterone (P(4)), corticosterone (B), and aldosterone (ALDO), sensitivity of adrenocortical cells to corticotrophin (ACTH) was lower in control males than females of S. virgatus. In S. jarrovii males, cellular sensitivity to ACTH was reduced by orchiectomy but was not restored to levels of intact controls by T replacement. By contrast, in S. undulatus, cellular sensitivity to ACTH was not affected by orchiectomy alone but was reduced by T replacement in orchiectomized males. Maximal rates of steroid production were less consistently affected by experimental treatments, but were lower in males than in females of S. virgatus and were dramatically reduced by T replacement in orchiectomized S. undulatus males. Overall, our experiments clearly demonstrate two distinct sources of variation in functional capacities of dispersed adrenocortical cells isolated from Sceloporus lizards: (1) naturally occurring differences between males and females (Carsia and John-Alder, 2003), and (2) species-dependent changes in response to surgical gonadectomy with or without exogenous testosterone. Sex differences and functional lability in adrenocortical cells are probably widespread among vertebrates and may be an important component of variation in output of the HPA.
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Affiliation(s)
- Rocco V Carsia
- Department of Cell Biology, University of Medicine and Dentistry of New Jersey, School of Osteopathic Medicine, Stratford, NJ 08084, USA
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Cox RM, Barrett MM, John-Alder HB. Effects of food restriction on growth, energy allocation, and sexual size dimorphism in Yarrow’s Spiny Lizard, Sceloporus jarrovii. CAN J ZOOL 2008. [DOI: 10.1139/z08-002] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Evolutionary biologists often view sexual size dimorphism (SSD) as a fixed genetic consequence of sexually antagonistic selection, but the actual magnitude of SSD may often be strongly dependent upon proximate environmental factors. Sexual differences in growth rate lead to male-biased SSD in wild populations of Yarrow’s Spiny Lizard ( Sceloporus jarrovii Cope, 1875), yet both sexes grow at similar rates under controlled laboratory conditions. We hypothesized that male-biased SSD in S. jarrovii reflects an obligatory sexual difference in energy allocation to growth versus competing functions, but that an ad libitum diet provides an energy surplus which overwhelms this sex-specific energetic trade-off. To test this hypothesis, we reared juveniles under high (3 crickets/d) and low (1 cricket/d) food availabilities. Food restriction dramatically reduced growth in both sexes but did not differentially affect growth of females relative to males. Food consumption did not differ between sexes, but males grew slightly faster than females at both levels of food availability, indicating a greater fractional allocation of available energy to growth. By contrast, females had larger fat bodies than did males, particularly under food restriction. This sexual difference in energy allocation to storage could explain the slightly higher growth rate of males relative to females.
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Affiliation(s)
- Robert M. Cox
- Rutgers University, Graduate Program in Ecology and Evolution, New Brunswick, NJ 08901, USA
- Rutgers University, Department of Animal Sciences, New Brunswick, NJ 08901, USA
- Rutgers University, Department of Ecology, Evolution and Natural Resources, New Brunswick, NJ 08901, USA
| | - Michele M. Barrett
- Rutgers University, Graduate Program in Ecology and Evolution, New Brunswick, NJ 08901, USA
- Rutgers University, Department of Animal Sciences, New Brunswick, NJ 08901, USA
- Rutgers University, Department of Ecology, Evolution and Natural Resources, New Brunswick, NJ 08901, USA
| | - Henry B. John-Alder
- Rutgers University, Graduate Program in Ecology and Evolution, New Brunswick, NJ 08901, USA
- Rutgers University, Department of Animal Sciences, New Brunswick, NJ 08901, USA
- Rutgers University, Department of Ecology, Evolution and Natural Resources, New Brunswick, NJ 08901, USA
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Cox RM, John-Alder HB. GROWING APART TOGETHER: THE DEVELOPMENT OF CONTRASTING SEXUAL SIZE DIMORPHISMS IN SYMPATRIC SCELOPORUS LIZARDS. HERPETOLOGICA 2007. [DOI: 10.1655/0018-0831(2007)63[245:gattdo]2.0.co;2] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Abstract
To examine the evolution of sexual size dimorphism (SSD), interspecific studies are often performed to generate hypotheses for the origin and maintenance of SSD. Although these methods are invaluable to our understanding of the evolution of SSD, they often quantify SSD for a species based on few populations. We found a significant sex-specific latitudinal cline in Plestiodon fasciatus (L., 1758) (= Eumeces fasciatus (L., 1758)), a species that was previously considered to be monomorphic for body size. Male body size significantly increased with increasing latitude, whereas female body size was relatively constant. Our findings argue for the importance of increased understanding and appreciation of intraspecific variation in SSD. We suggest that a more integrated approach to SSD be employed, where both intraspecific and interspecific variation is considered. We provide a foundation for posing hypotheses of the causes and consequences of SSD in P. fasciatus and perhaps other members of the species group.
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Affiliation(s)
- Briar J. Howes
- Department of Biology, Queen’s University, Kingston, ON K7L 3N6, Canada
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