AGEING AND RS

The role of ageing in the maintenance of variability in male reproductive success

 Partecipanti

Mappa

 Word cloud

Esplora la "nuvola delle parole (Word Cloud) per avere un'idea di massima del progetto.

 Obiettivo del progetto (Objective)

'Sexual selection is expected to generate intense directional selection on pre- and post-copulatory traits, however such traits typically exhibit considerable variation. This presents a paradox because directional selection is expected to progressively erode genetic variation in sexually-selected traits by driving them to fixation. Understanding how variance in male reproductive success is maintained, despite persistent directional selection for certain phenotypes, constitutes one of the major challenges in evolutionary biology. An increasing body of work shows that senescence is a biologically relevant evolutionary force, but its consequences at an evolutionary level remain poorly understood as it is a surprisingly under-investigated source of variation in reproductive success. The broad aim of this project is to study the role of ageing in the maintenance of variability in male reproductive success. The proposed experiments are designed to investigate the effects of sperm ageing and male ageing on male reproductive success with a specific focus on postcopulatory traits, using the guppy (Poecilia reticulata) as a model species. I will investigate the evolutionary implications of sperm senescence by determining how ageing influences sperm performance and by identifying age-related damage to sperm DNA and structure. I will examine the consequences of fertilization by aged sperm on offspring fitness and I will study the effects of sperm ageing on sperm competitive fertilization ability. I will use a quantitative genetic approach to investigate trade-offs between males’ pre- and postcopulatory reproductive investment in relation to age, and reveal the genetic basis of such life-history trajectories. This work will provide new insights into the factors that maintain high variability in male reproductive success and the evolutionary process of ageing, thus addressing a key unresolved problem in evolutionary biology.'

Introduzione (Teaser)

European researchers are investigating sexual selection and male reproductive success characterised by features such as swimming ability of sperm. The effects of ageing are proving to be particularly significant.

Descrizione progetto (Article)

Sexual selection is expected to drive intense selection pressure on traits selected for both before and after copulation, and so reduce variation. However, these features remain surprisingly very diverse and one of the main challenges in evolutionary biology is to explain this phenomenon.

The project 'The role of ageing in the maintenance of variability in male reproductive success' (AGEING AND RS) is researching sperm senescence in the guppy Poecilia reticulata as a possible contributor to diversity.

During the first phase of the project, scientists found that ovarian fluid collected from the female genital tract offsets the deleterious effects of ageing on sperm quality. Female guppies can store the sperm for up to six months.

However, during male storage, older sperm showed less motility than their freshly produced counterparts. As sperm motility is a major determinant of competitive fertilisation success in guppies, males with older sperm will not be favoured. As female storage mediates the effects of ageing on sperm, however, it may be that the female uses polyandry or multiple mates to select against aged sperm.

The AGEING AND RS team also found that ageing sperm reduces the chances of fertilisation when there is sperm from other males present. Significantly perhaps, this effect is not seen in the absence of competitor's sperm. Results also indicate that sperm age affects the resulting offspring.

Project findings suggest that sperm ageing is an important factor that may shape a number of male and female traits, extending to effects on the offspring. Future results promise to shed more light on how features of male reproductive success can remain diverse despite selection pressures.