Reproductive biology and senescence impact on postcopulatory sexual selection in a wild polyandrous bird, the North African houbara bustard (Chlamydotis undulata undulata)

Started in december 2020

Private funding (Reneco)

Supervisors: Gabriele Sorci (Biogéosciences), Janaina Torres Carreira (Reneco International Wildilfe consultants LLC) & Michel Saint Jalme (Muséum national d’histoire naturelle)

Defense 26 june 2024

Abstract

Polyandry, when females mate with multiple males, increases the opportunity for sexual selection to operate, because in addition to competition between males for access to the female (pre-copulatory sexual selection), sperm from different males also compete for fertilization (post-copulatory sexual selection). This often results in most offspring being sired by the last male, a phenomenon called last male precedence (LMP). In addition to mating order, sperm quantity and quality can also influence the outcome of sperm competition. As males age, sperm quality and quantity decrease, resulting in reduced reproductive success. In the North African houbara bustard (Chlamydotis undulata undulata), females are polyandrous, and males suffer from reproductive senescence. The thesis aims at improving our understanding of the reproductive biology of houbara bustards, reproductive senescence and its impact on male reproductive success and post-copulatory selection. In the first part, to improve the knowledge of the species’ physiology of reproduction and to construct a solid base for houbara reproductive anatomy and sperm morphology and later storage mechanism in the female tract, we explored anatomy and histology of the female and male reproductive systems during and out of the breeding season and sperm morphology was described. In the second part, we investigated the underlying mechanisms of LMP and the storage dynamics within the oviduct during competitive inseminations. In the third part, we investigated male reproductive senescence and its relationship with post-copulatory selection. This work was divided into four sections to investigate different aspects of reproductive ageing. Firstly, we examined seasonal testosterone levels and a possible age-related pattern. Second, we investigated a possible trade-off between sperm number and quality across ages. Thirdly, to test male age, sperm age, and their possible interaction on sperm quality and reproductive success, sperm ageing in the male tract was investigated by controlling the timing of collection intervals for young and old males. Finally, LMP was studied under controlled experimental conditions to disentangle the effects of male age, mating order, and sperm quality on siring success. This thesis presents the first description of houbara reproductive anatomy and histology and sperm morphology classification. Active sperm displacement is likely to be the main mechanism of LMP. There was no evidence of an age-related pattern of testosterone levels throughout the breeding season. Peak testosterone levels preceded peaks in sexual behaviour and sperm characteristics. We found a positive covariation between sperm quantity and several sperm quality traits, and male age did not influence the strength of this covariation. No evidence of sperm ageing during prolonged storage in the male tract was observed. On the contrary, sperm collected at longer intervals had higher quality, which was reflected in higher hatching success. Consistent with previous work, older males had lower sperm number, volume, motility and velocity and sired offspring with impaired growth rate. Finally, we found no evidence of an age effect on LMP. Regardless of age, sperm from the last male in the insemination sequence sired approximately 60% of the offspring. Overall, this work has provided a better understanding and new insights into the reproductive biology of houbara bustards and the mechanisms of post copulatory selection.

Keywords

Sperm competition, reproductive senescence, sperm quality, sperm storage, anatomy, houbara bustard

extrait:

lien_externe:

titre:

Effet de l’âge sur la préséance du dernier mâle et sur la sélection sexuelle post-copulatoire chez l’outarde Houbara d’Afrique du Nord

date_de_debut_these:

décembre 2020

nom:

Meunier

date_de_debut_these_numerique:

202012

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kc_raw_content:

Reproductive biology and senescence impact on postcopulatory sexual selection in a wild polyandrous bird, the North African houbara bustard (Chlamydotis undulata undulata)

Started in december 2020

Private funding (Reneco)

Supervisors: Gabriele Sorci (Biogéosciences), Janaina Torres Carreira (Reneco International Wildilfe consultants LLC) & Michel Saint Jalme (Muséum national d’histoire naturelle)

Defense 26 june 2024

 

Abstract

Polyandry, when females mate with multiple males, increases the opportunity for sexual selection to operate, because in addition to competition between males for access to the female (pre-copulatory sexual selection), sperm from different males also compete for fertilization (post-copulatory sexual selection). This often results in most offspring being sired by the last male, a phenomenon called last male precedence (LMP). In addition to mating order, sperm quantity and quality can also influence the outcome of sperm competition. As males age, sperm quality and quantity decrease, resulting in reduced reproductive success. In the North African houbara bustard (Chlamydotis undulata undulata), females are polyandrous, and males suffer from reproductive senescence. The thesis aims at improving our understanding of the reproductive biology of houbara bustards, reproductive senescence and its impact on male reproductive success and post-copulatory selection. In the first part, to improve the knowledge of the species’ physiology of reproduction and to construct a solid base for houbara reproductive anatomy and sperm morphology and later storage mechanism in the female tract, we explored anatomy and histology of the female and male reproductive systems during and out of the breeding season and sperm morphology was described. In the second part, we investigated the underlying mechanisms of LMP and the storage dynamics within the oviduct during competitive inseminations. In the third part, we investigated male reproductive senescence and its relationship with post-copulatory selection. This work was divided into four sections to investigate different aspects of reproductive ageing. Firstly, we examined seasonal testosterone levels and a possible age-related pattern. Second, we investigated a possible trade-off between sperm number and quality across ages. Thirdly, to test male age, sperm age, and their possible interaction on sperm quality and reproductive success, sperm ageing in the male tract was investigated by controlling the timing of collection intervals for young and old males. Finally, LMP was studied under controlled experimental conditions to disentangle the effects of male age, mating order, and sperm quality on siring success. This thesis presents the first description of houbara reproductive anatomy and histology and sperm morphology classification. Active sperm displacement is likely to be the main mechanism of LMP. There was no evidence of an age-related pattern of testosterone levels throughout the breeding season. Peak testosterone levels preceded peaks in sexual behaviour and sperm characteristics. We found a positive covariation between sperm quantity and several sperm quality traits, and male age did not influence the strength of this covariation. No evidence of sperm ageing during prolonged storage in the male tract was observed. On the contrary, sperm collected at longer intervals had higher quality, which was reflected in higher hatching success. Consistent with previous work, older males had lower sperm number, volume, motility and velocity and sired offspring with impaired growth rate. Finally, we found no evidence of an age effect on LMP. Regardless of age, sperm from the last male in the insemination sequence sired approximately 60% of the offspring. Overall, this work has provided a better understanding and new insights into the reproductive biology of houbara bustards and the mechanisms of post copulatory selection.

 

Keywords

Sperm competition, reproductive senescence, sperm quality, sperm storage, anatomy, houbara bustard