Sex allocation theory aids species conservation

Robertson, Bruce C.; Elliott, Graeme; Eason, Daryl; Clout, Mick N.; Gemmell, Neil J.

doi:10.1098/rsbl.2005.0430

Cited by 93 publications

(86 citation statements)

References 17 publications

(32 reference statements)

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“…Considering that breeding from highly inbred individuals is not necessarily bad because they might still be genetically important at population level, in practice, the manager of this captive population might be able to combine inbred females with unrelated or slightly unrelated partners, resulting in a non-or slightly inbred offspring (very likely a daughter if our results are considered), which help to solve the short term practical problem of surplus males within the EEP of the species. This practice suggested for captive Cuvier's gazelle agrees with that outlined by other authors: in captive breeding populations where offspring sex ratio is dependent on female condition, manipulation of offspring sex ratios should be considered as a management option as it may increase the number of females that can be released (Lenz et al, 2007, Robertson et al, 2006, Tella, 2001). …”

Section: Implication To Ex Situ Conservation Programssupporting

confidence: 63%

Mother traits and offspring sex in two threatened gazelle species in captivity

Moreno

Ibáñez

Barbosa

2011

Journal for Nature Conservation

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Since threatened species are generally incapable of surviving in their natural environments, ex situ conservation programs are required to preserve them from total extinction. Captive breeding provides the tool to rear sustained populations. Knowledge about biology of such species is critical for managing such breeding programmes. In this paper we look at the sex variation in calves surviving to 30 days in captive populations of two endangered polygynous gazelles, Gazella cuvieri and Gazella dama mhorr. We examined which of the following mother traits may affect sex allocation: her age, experience and inbreeding coefficient. Because twins are quite common in Cuvier's gazelle, we also analyze whether offspring sex is mediated by litter size in this gazelle.In both species the overall sex ratio did not differ from unity at the age of 30 days.These results support the suggestion that for a given population to be in equilibrium, a 1:1 calf sex ratio is to be expected, with females in good condition producing sons and females in poor condition producing daughters. We also found that offspring sex is not significantly related to the same mother traits in the two gazelles studied. Cuvier's gazelle findings showed that only maternal inbreeding influenced offspring sex, the less inbred the mother the higher the probability of producing sons. In contrast, none of the maternal traits studied were related to offspring sex in Mohor gazelle. Two non exclusive explanations are given to justify differences observed between these two species; one relate to a probable differential cost of producing either sex; the other refers to the actual homozygosis level in captive populations of each species. For Cuvier's gazelle litter size has no effect on offspring sex when the sex of the littermate is taken into account. This result fit predictions derived from Trivers-Willard model: mother in good conditions (less inbred) produce the sex with higher fitness returns (i.e., male), no matter if born at single or twins brood. Many variables are likely to affect progeny sex ratio. We have presently examined only a few. But our results might be of interest in management decisions and conservation programs such as reintroductions.

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Section: Implication To Ex Situ Conservation Programssupporting

confidence: 63%

Mother traits and offspring sex in two threatened gazelle species in captivity

Moreno

Ibáñez

Barbosa

2011

Journal for Nature Conservation

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“…However, differential maternal allocation can lead to an offspring sex ratio bias in some systems, which could hamper the management of conserved species (Robertson et al 2006). Indeed, supplementary feeding of the critically endangered kakapo Strigops habroptilus to enhance breeding frequency and breeding success led to an unfortunate offspring sex ratio bias towards males.…”

Section: Discussionmentioning

confidence: 99%

“…Indeed, supplementary feeding of the critically endangered kakapo Strigops habroptilus to enhance breeding frequency and breeding success led to an unfortunate offspring sex ratio bias towards males. Robertson et al (2006) optimized the feeding regime of the kakapo females and successfully removed the bias in sex ratio. Doing so, they documented the first example of a successful manipulation of maternal allocation through female diet for species conservation.…”

Section: Discussionmentioning

confidence: 99%

Watching sexy displays improves hatching success and offspring growth through maternal allocation

Loyau

Lacroix²

2010

Proc. R. Soc. B.

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Male attractiveness can have tremendous effects on the fitness of his offspring via good genes, but also via enhanced maternal allocation of resources. Yet the proximate mechanisms influencing differential maternal allocation in relation to male sexiness are poorly known. Here, we studied the importance of visual stimulation for maternal allocation in the Houbara bustard, a vulnerable bird species bred in captivity to support wild populations. Artificial insemination allowed controlling for potential confounding factors, such as a male's territory quality, social interactions or sperm quality/quantity, probably linked to mate attractiveness. We show that artificially inseminated females stimulated by highly displaying males increased their hatching success, owing to increased fertilization success. The females also increased the allocation of maternal androgens in their eggs, leading to an increase of circulating testosterone and growth rate in chicks. Hence, visual stimulation of the females can promote differential maternal allocation and favour offspring fitness. Our results further suggest that using artificial insemination for species conservation without appropriate stimulation of the breeding females probably has negative impacts on their breeding performance and therefore on population viability.

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“…Sex ratio is an important aspect of population demography and deviations from parity can have catastrophic consequences for the viability of small populations [21]. If a species alters the sex ratio of its progeny in response to the quality of the environment then developing management strategies based on demographic models that assume an equal sex ratio Grazing influences bird sex ratios G. L. Prior et al 959 could have important repercussions for species nesting in degraded habitats [22]. …”

Section: Discussionmentioning

confidence: 99%

Birds bias offspring sex ratio in response to livestock grazing

et al. 2011

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Livestock grazing, which has a large influence on habitat structure, is associated with the widespread decline of various bird species across the world, yet there are few experimental studies that investigate how grazing pressure influences avian reproduction. We manipulated grazing pressure using a replicated field experiment, and found that the offspring sex ratio of a common upland passerine, the meadow pipit Anthus pratensis , varied significantly between grazing treatments. The proportion of sons was lowest in the ungrazed and intensively grazed treatments and highest in treatments grazed at low intensity (by sheep, or a mixture of sheep and cattle). This response was not related to maternal body condition. These results demonstrate the sensitivity of avian reproductive biology to variation in local conditions, and support growing evidence that too much grazing, or the complete removal of livestock from upland areas, is detrimental for common breeding birds.

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Sex allocation theory aids species conservation

Cited by 93 publications

References 17 publications

Mother traits and offspring sex in two threatened gazelle species in captivity

Mother traits and offspring sex in two threatened gazelle species in captivity

Watching sexy displays improves hatching success and offspring growth through maternal allocation

Birds bias offspring sex ratio in response to livestock grazing

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