Incubation Temperature Modifies Sex Ratio of Hatchlings in Collared Lizards, <i>Crotaphytus collaris</i>

Santoyo-Brito, Enrique; Anderson, Matthew; Fox, Stanley F.

doi:10.1670/15-167

Cited by 5 publications

(3 citation statements)

References 25 publications

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“…None of the 12 females became gravid. Due to the success of the same capture-oviposition methods used here in maintaining pregnancy of spring-captured females, and subsequently producing viable eggs and hatchlings in previous studies in our laboratory (Santoyo-Brito et al 2012, we are confident the failure to obtain eggs is due to the natural history of this species, not laboratory techniques, at least for those techniques from the spring onward. We acknowledge that laboratory conditions during the artificial brumation might have somehow interfered with successful subsequent oviposition of potentially fertilized fall juvenile females.…”

Section: Parentage Analysismentioning

confidence: 74%

“…Postbrumation lizards were held in individual 37.8-L glass aquaria under standard laboratory conditions (bricks for basking and cardboard shelter for refuging: overhead incandescent light bulb with reflector at one end of the cage to create a thermal gradient of 20–25°C during the day; overhead ultraviolet lights; water dish with water available at all times and cage walls and bricks watered daily; and live vitamin-dusted crickets and cockroaches offered daily) for 4–6 mo to observe possible oviposition of fertile eggs from their exposure to the putative juvenile males in the field the prior October. Oviposition chambers (Santoyo-Brito et al 2012) were held ready if any female showed signs of gravidity. Our objective was then to incubate those eggs in the laboratory to determine if they were fertilized and viable.…”

Section: Methodsmentioning

confidence: 99%

“…Oviposition chambers (Santoyo-Brito et al 2012) were held ready if any female showed signs of gravidity. Our objective was then to incubate those eggs in the laboratory to determine if they were fertilized and viable.…”

Section: Female Availability For Mating In the Fallmentioning

confidence: 99%

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When do Young Collared Lizards (Crotaphytus collaris) First Copulate with and Fertilize Females?

et al. 2023

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In many species, males are larger and more colorful than females. This has often evolved by sexual selection, and the sexual dimorphism and dichromatism is observed once individuals reach adulthood. Such sexual differences are presented by Collared Lizards, Crotaphytus collaris. However, sexual dichromatism of a different sort than that expressed in adults is seen in juveniles before their first brumation. Late-season juvenile males develop bright orange dorsolateral bars and begin to defend territories and form pair bonds with females. Furthermore, the largest, late-season, putative juvenile males have mature sperm on their hemipenes. Paternity analyses using polymerase chain reaction of eight microsatellite loci revealed that a significant number of putative juvenile males, which were not seen during intensive fieldwork at our study site the following year, sired offspring with females who were juveniles, yearlings, or adults in the fall. Either females were fertilized by these males in the fall (and those females either stored sperm or arrested development of embryos overwinter), or they were fertilized by surviving fall juvenile males (i.e., yearlings) early the next spring, who subsequently died before we began our spring-summer field surveys. The majority of our data indicates the second possibility is true. First, adults and yearlings of both sexes begin brumation in the fall, weeks or months before October when larger putative juvenile males display sexual dichromatism and have mature sperm on their hemipenes. Females of these age classes are not available for copulation in October but are in early spring. Second, we collected juvenile females from the field in October and held them individually without exposure to males in the laboratory through brumation and beyond through spring and summer. None of these females became gravid. Our results indicate that although putative juvenile males possess mature sperm in the late fall, they wait until the following spring to fertilize adults of all age classes. Many of these males subsequently die early in the season but attain (posthumous) fitness by mating early in the spring before yearling and adult males become fully territorial and sexually active.

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Section: Parentage Analysismentioning

confidence: 74%

Section: Methodsmentioning

confidence: 99%

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When do Young Collared Lizards (Crotaphytus collaris) First Copulate with and Fertilize Females?

et al. 2023

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Evidence for sex microchromosomes in a species with temperature-influenced sex determination (Crotaphytus collaris)

Wiggins

Santoyo-Brito

Scales

et al. 2018

Preprint

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Keywords 6 7Sex-determining mechanism, genotypic sex determination, temperature-dependent sex 8 determination, gene-dosage, sex microchromosome, reptile, Crotaphytus collaris 9 10 Abstract 11 12The characteristics of a species' evolution can be powerfully influenced by its mode of sex 13 determination and, indeed, sex determination mechanisms vary widely among eukaryotes. In 14 non-avian reptiles, sex was long thought to be determined bimodally, either by temperature or 15 genetics. Here we add to the growing evidence that sex determining mechanisms in reptiles fall 16 along a continuum rather than existing as a mutually exclusive dichotomy. Using qPCR, we 17 demonstrate that the lizard Crotaphytus collaris possesses sex-based gene dosage consistent with 18 the presence of sex michrochromosomes, despite that extreme incubation temperatures can 19 influence hatchling sex ratio. Our results suggest a temperature override that switches genotypic 20 females to phenotypic males at high and low temperatures. 21 22 23 24 25the authors of this study point out that their sample size was low, this indicates a 64 temperature influence on sex determination in C. collaris. However, even at low and high 65 treatments this study did not find ratios of either sex nearing 100%. These findings hint at a more 66 complex mechanism for sex determination than pure TSD or pure GSD in C. collaris, as 67

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Gene Dose Indicates Presence of Sex Chromosomes in Collared Lizards (Crotaphytus collaris), a Species with Temperature-Influenced Sex Determination

et al. 2020

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Incubation Temperature Modifies Sex Ratio of Hatchlings in Collared Lizards, Crotaphytus collaris

Cited by 5 publications

References 25 publications

When do Young Collared Lizards (Crotaphytus collaris) First Copulate with and Fertilize Females?

When do Young Collared Lizards (Crotaphytus collaris) First Copulate with and Fertilize Females?

Evidence for sex microchromosomes in a species with temperature-influenced sex determination (Crotaphytus collaris)

Gene Dose Indicates Presence of Sex Chromosomes in Collared Lizards (Crotaphytus collaris), a Species with Temperature-Influenced Sex Determination

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