Age at Maturity Influences Adult Sex Ratio in the Turtle Malaclemys terrapin

Lovich, Jeffrey E.; Gibbons, J. Whitfield

doi:10.2307/3545132

Cited by 113 publications

(78 citation statements)

References 61 publications

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“…Differences in shell strength could also have effects on turtle population structure. The female-biased ratios seen in some turtle populations (e.g., Lovich and Gibbons, 1990) could be due to many factors, but predation resistance is at least one. Clearly, studies on predator encounter rates and survival rates for many turtle species are crucial for understanding the impact of differences in shell mechanics on other aspects of turtle biology.…”

Section: Resultsmentioning

confidence: 99%

Sexual Dimorphism in the Greek Tortoise: A Test of the Body Shape Hypothesis

Kaddour¹,

Mouden²,

Slimani³

et al. 2008

Chelonian Conservation and Biology

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In most animal species, it is expected that females should exhibit a greater abdominal volume than males to hold the progeny, when compared with females, males should exhibit more developed attributes that enhance mobility. We tested this hypothesis in the Greek tortoise. In chelonians, a reduction of the openings in the shell improves protection against predation but also constrains the abdominal volume and limits the space available to move the limbs. As expected, our data show that the shell provides a larger abdominal volume relative to tortoise size in females than in males. In males, deep notches in the shell and a reduction of several plastron plates offer more freedom to the limbs and to the tail; these characteristics presumably enhance mating success. Further studies are necessary to assess the applicability of these results in other chelonians, notably freshwater and marine turtles

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Section: Resultsmentioning

confidence: 99%

Sexual Dimorphism in the Greek Tortoise: A Test of the Body Shape Hypothesis

Kaddour¹,

Mouden²,

Slimani³

et al. 2008

Chelonian Conservation and Biology

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“…Biases in the ASR can emerge via a number of mutually nonexclusive demographic pathways (11,17,18). For instance, sex biases may occur at conception or birth (19), or the survival of male and female juveniles may differ to the extent that fewer of one sex reach adulthood (20).…”

Section: Adult Sex Ratio (Asr) Is a Central Concept In Population Biomentioning

confidence: 99%

“…For instance, sex biases may occur at conception or birth (19), or the survival of male and female juveniles may differ to the extent that fewer of one sex reach adulthood (20). Furthermore, sex differences in adult survival or maturation rates could create a shortage of the sex that has higher mortality (4) or slower maturation (18), and if emigration is not compensated Significance Sex biases are widespread in nature and represent a fundamental component of sexual selection and population biology-but at which point in life history do these biases emerge? We report a detailed individual-based demographic analysis of an intensively studied wild bird population to evaluate origins of sex biases and their consequences on mating strategies and population dynamics.…”

Section: Adult Sex Ratio (Asr) Is a Central Concept In Population Biomentioning

confidence: 99%

Sex-specific early survival drives adult sex ratio bias in snowy plovers and impacts mating system and population growth

Eberhart-Phillips

Küpper

Miller

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Adult sex ratio (ASR) is a central concept in population biologyand a key factor in sexual selection, but why do most demographic models ignore sex biases? Vital rates often vary between the sexes and across life history, but their relative contributions to ASR variation remain poorly understood-an essential step to evaluate sex ratio theories in the wild and inform conservation. Here, we combine structured two-sex population models with individual-based mark-recapture data from an intensively monitored polygamous population of snowy plovers. We show that a strongly male-biased ASR (0.63) is primarily driven by sexspecific survival of juveniles rather than adults or dependent offspring. This finding provides empirical support for theories of unbiased sex allocation when sex differences in survival arise after the period of parental investment. Importantly, a conventional model ignoring sex biases significantly overestimated population viability. We suggest that sex-specific population models are essential to understand the population dynamics of sexual organisms: reproduction and population growth are most sensitive to perturbations in survival of the limiting sex. Overall, our study suggests that sex-biased early survival may contribute toward mating system evolution and population persistence, with implications for both sexual selection theory and biodiversity conservation.ASR | Charadrius nivosus | mark-recapture | sex allocation | two-sex matrix model

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“…There may be several causes of this variation. First, sex-speciWc diVerences in age-at-maturity or migration patterns tend to skew sex ratios in favour of the earlier-maturing sex (Lovich and Gibbons 1990;Girondot and Pieau 1993) or the sex that migrates later (Reynolds et al 1986;Colwell and Oring 1988). Second, sex-speciWc diVerences in mortality may be caused by diVerential susceptibility to predators (Britton and Moser 1982;Hairston et al 1983), low resource levels (Clutton-Brock et al 1991;Mulvihill et al 1992), inter-or intra-sexual aggression (Sherman and Morton 1984;Hailey and Willemsen 2000), or the costs of parental care (Donald combination, making them diYcult to disentangle without accounting for their possible covariance.…”

Section: Introductionmentioning

confidence: 99%

Environmental factors influencing adult sex ratio in Trinidadian guppies

2009

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Sex ratios can influence mating behaviour, population dynamics and evolutionary trajectories; yet the causes of natural sex ratio variation are often uncertain. Although secondary (birth) sex ratios in guppies (Poecilia reticulata) are typically 1:1, we recorded female-biased tertiary (adult) sex ratios in about half of our 48 samples and male-biased sex ratios in none of them. This pattern implies that some populations experience male-biased mortality, perhaps owing to variation in predation or resource limitation. We assessed the effects of predation and/or inter-specific resource competition (intraguild predation) by measuring the local catch-per-unit-effort (CPUE) of species (Rivulus killifish and Macrobrachium prawns) that may differentially prey on male guppies. We assessed the effects of resource levels by measuring canopy openness and algal biomass (chlorophyll a concentration). We found that guppy sex ratios were increasingly female-biased with increasing CPUE of Macrobrachium, and perhaps also Rivulus, and with decreasing canopy openness. We also found an interaction between predators and resource levels in that the effect of canopy openness was greatest when Macrobrachium CPUE was highest. Our study thus also reveals the value of simultaneously testing multiple environmental factors that may drive tertiary sex ratio variation.

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Age at Maturity Influences Adult Sex Ratio in the Turtle Malaclemys terrapin

Cited by 113 publications

References 61 publications

Sexual Dimorphism in the Greek Tortoise: A Test of the Body Shape Hypothesis

Sexual Dimorphism in the Greek Tortoise: A Test of the Body Shape Hypothesis

Sex-specific early survival drives adult sex ratio bias in snowy plovers and impacts mating system and population growth

Environmental factors influencing adult sex ratio in Trinidadian guppies

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