Sperm competition and sperm phenotype

Pizzari, Tommaso; Parker, Geoff A.

doi:10.1016/b978-0-12-372568-4.00006-9

Cited by 217 publications

(308 citation statements)

References 164 publications

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“…In addition, although we looked over five copulations, trade-offs may only be detected over a lifetime. A negative association between sperm size and number is a key assumption of sperm competition theory (Pizzari and Parker, 2009), but one for which there is only limited support (for example, see Pitnick, 1996;Oppliger et al, 1998). This is, at least, partly because of the difficulties in assessing the predicted negative association (Pitnick, 1996;Pizzari and Parker, 2009), but in any case, we find no evidence indicative of a trade-off-with the caveats given above, which make the test rather weak.…”

Section: Discussioncontrasting

confidence: 47%

Response to selection and realized heritability of sperm length in the yellow dung fly (Scathophaga stercoraria)

Dobler

Hosken

2009

Heredity

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Sperm length shows considerable phenotypic variation both inter-and intra-specifically, but a general explanation for this variation is lacking. In addition, our understanding of the genetic variation underlying sperm length variation is also limited because there have been few studies on the genetics of sperm size. One factor that could explain the variation in sperm length is that length influences sperm competitiveness, and there is some evidence for this. However, in yellow dung flies (Scathophaga stercoraria), microevolutionary responses to experimental variation at levels of sperm competition indicate that sperm length does not influence sperm competitiveness, although this lack of response may simply indicate sperm length lacks evolutionary potential (that is, it is constrained in some way), in spite of evidence that sperm length is heritable. Here we report on a laboratory study, in which we artificially selected upwards and downwards on sperm length in S. stercoraria. We found that sperm length significantly diverged after four generations of selection, but the response to selection was asymmetrical: upward selection generated a rapid response, but downward did not. We estimated the realized heritability of sperm length to be approximately 50%, which is consistent with previous sire-son estimates. We also assessed the fertility of males from upward and downward lines and found they did not differ. Results are discussed in the context of sperm competition.

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Section: Discussioncontrasting

confidence: 47%

Response to selection and realized heritability of sperm length in the yellow dung fly (Scathophaga stercoraria)

Dobler

Hosken

2009

Heredity

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“…Nevertheless, understanding the functional significance of these patterns remain important challenges for the future. As Pizzari and Parker (2009) have recently suggested, the tools of multivariate selection analyses (see Lande and Arnold, 1983) are likely to prove helpful for exploring such patterns by unveiling the direction, strength and form of selection acting on these multifarious traits.…”

Section: Jp Evansmentioning

confidence: 99%

“…Sperm competition, the contest between ejaculates to fertilize eggs (Parker, 1970), is a common and powerful evolutionary force generating intense selection on ejaculates (Birkhead and M ller, 1998;Pizzari and Parker, 2009). Although sperm competition theory largely focuses on variation in traits linked to sperm production, including sperm numbers and testes size, there is increasing evidence that differences in the relative 'quality' of competing ejaculates can also generate variation in competitive fertilization rates (Snook, 2005).…”

Section: Introductionmentioning

confidence: 99%

Patterns of genetic variation and covariation in ejaculate traits reveal potential evolutionary constraints in guppies

Evans

2010

Heredity

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Ejaculates comprise multiple and potentially interacting traits that determine male fertility and sperm competitiveness. Consequently, selection on these traits is likely to be intense, but the efficacy of selection will depend critically on patterns of genetic variation and covariation underlying their expression. In this study, I provide a prospective quantitative genetic analysis of ejaculate traits in the guppy Poecilia reticulata, a highly promiscuous livebearing fish. I used a standard paternal half-sibling breeding design to characterize patterns of genetic (co)variation in components of sperm length and in vitro sperm performance. All traits exhibited high levels of phenotypic and additive genetic variation, and in several cases, patterns of genetic variation was consistent with Y-linkage. There were also highly significant negative genetic correlations between the various measures of sperm length and sperm performance. In particular, the length of the sperm's midpiece was strongly, negatively and genetically correlated with sperm's swimming velocity-an important determinant of sperm competitiveness in this and other species. Other components of sperm length, including the flagellum and head, were independently and negatively genetically correlated with the proportion of live sperm in the ejaculate (sperm viability). Whether these relationships represent evolutionary trade-offs depends on the precise relationships between these traits and competitive fertilization rates, which have yet to be fully resolved in this (and indeed most) species. Nevertheless, these prospective analyses point to potential constraints on ejaculate evolution and may explain the high level of phenotypic variability in ejaculate traits in this species.

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“…This more recent work is beginning to reveal that polyandry has ramifications-hitherto ignored-that far exceed the remits of sexual selection and sexual conflict, and have profound implications for a number of other fundamental evolutionary and ecological processes such as sex allocation, social networks, altruism and cooperation, sex-biased gene expression, selfish genetic elements (SGEs), sexually transmitted infections, population extinction and management. Up until now however, reviews of polyandry have been largely focused rather narrowly on the proximate mechanisms of sperm competition and cryptic female choice [6,7]. Very little has been done to cover the burgeoning development of studies considering the evolutionary ecology of polyandry in a wider, interdisciplinary context.…”

Section: Introductionmentioning

confidence: 99%