Sperm competition and sperm length influence the rate of mammalian spermatogenesis

Ramm, Steven A.; Stockley, Paula

doi:10.1098/rsbl.2009.0635

Cited by 77 publications

(94 citation statements)

References 28 publications

(57 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In addition to huge variation in body size and metabolic rates, generation time varies almost 10-fold, with the shortest generation time observed in prosimians [∼3 y in galago and mouse lemurs (18)] and the longest generation time observed in humans (∼29 y). Species also differ in the strength of sperm competition and rates of spermatogenesis: monkeys have a shorter spermatogenetic division, and thus consequently produce more sperm per unit time than do apes (19). Thus, even if the per cell division mutation rate remained constant, we should expect differences in yearly mutation rates among species.…”

Section: Significancementioning

confidence: 97%

Variation in the molecular clock of primates

Moorjani

Amorim

Arndt

et al. 2016

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

211

187

View full text Add to dashboard Cite

Events in primate evolution are often dated by assuming a constant rate of substitution per unit time, but the validity of this assumption remains unclear. Among mammals, it is well known that there exists substantial variation in yearly substitution rates. Such variation is to be expected from differences in life history traits, suggesting it should also be found among primates. Motivated by these considerations, we analyze whole genomes from 10 primate species, including Old World Monkeys (OWMs), New World Monkeys (NWMs), and apes, focusing on putatively neutral autosomal sites and controlling for possible effects of biased gene conversion and methylation at CpG sites. We find that substitution rates are up to 64% higher in lineages leading from the hominoid-NWM ancestor to NWMs than to apes. Within apes, rates are ∼2% higher in chimpanzees and ∼7% higher in the gorilla than in humans. Substitution types subject to biased gene conversion show no more variation among species than those not subject to it. Not all mutation types behave similarly, however; in particular, transitions at CpG sites exhibit a more clocklike behavior than do other types, presumably because of their nonreplicative origin. Thus, not only the total rate, but also the mutational spectrum, varies among primates. This finding suggests that events in primate evolution are most reliably dated using CpG transitions. Taking this approach, we estimate the human and chimpanzee divergence time is 12.1 million years, and the human and gorilla divergence time is 15.1 million years. molecular clock | mutation rate | primate evolution | CpG transition rate | human-ape divergence time G ermline mutations are the ultimate source of genetic differences among individuals and species. They are thought to arise from a combination of errors in DNA replication (e.g., the chance misincorporation of a base pair) or damage that is unrepaired by the time of replication (e.g., the spontaneous deamination of methylated CpG sites) (1). If mutations are neutral (i.e., do not affect fitness), then the rate at which they arise will be equal to the substitution rate (2). A key consequence is that if mutation rates remain constant over time, substitution rates should likewise be constant.This assumption of constancy of substitution rates plays a fundamental role in evolutionary genetics by providing a molecular clock with which to date events inferred from genetic data (3). Notably, important events in human evolution for which there is no fossil record (e.g., when humans and chimpanzees split, or when anatomically modern humans left Africa) are dated using a mutation rate obtained from contemporary pedigrees or phylogenetic analysis, assuming the per year rate has remained unchanged for millions of years (4).However, we know from studies of mammalian phylogenies, as well as of other taxa, that there can be substantial variation in substitution rates per unit time (5-7). In particular, there is the well-known hypothesis of a "generation time effect" on substitution rates,...

show abstract

Section: Significancementioning

confidence: 97%

Variation in the molecular clock of primates

Moorjani

Amorim

Arndt

et al. 2016

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

211

187

View full text Add to dashboard Cite

show abstract

“…It should be noted, however, that adaptations to sperm production in response to postcopulatory sexual selection can also involve increases in the density and functional efficiency of the sperm-producing tissue across testes of identical size [45][46][47][48] . Moreover, in addition to sperm competition, selection on testes size can occur through selection against sperm depletion 49 , with males that monopolize more females and thus mate more frequently losing paternity due to sperm depletion 50 .…”

Section: Discussionmentioning

confidence: 99%

Female monopolization mediates the relationship between pre- and postcopulatory sexual traits

et al. 2014

View full text Add to dashboard Cite

Theory predicts a trade-off between investments in precopulatory (ornaments and armaments) and postcopulatory (testes and ejaculates) sexual traits due to the costs associated with their growth and maintenance within the finite energy resources available. Empirical studies, however, have revealed considerable inconsistency in the strength and direction of relationships among these sexual traits. Ambiguity may result from variance in the marginal benefits gained by increasing investments in either pre-or postcopulatory sexual traits. Here, in a broad comparative study, we test the prediction that the relationship between pre-and postcopulatory sexual traits differs among taxa relative to the importance of male-male contest competition within them. We find that covariance between pre-and postcopulatory sexual traits gradually shifts from strongly positive to strongly negative with increasing male-male contest competition. Thus, our findings reveal a potentially unifying explanation for the oftentimes inconsistent relationships in the strength and direction of covariance among sexual traits.

show abstract

“…Typically, males that inseminate greater numbers of sperm achieve greater fertilization success (Martin et al 1974, Parker 1982. As the size of a males' testes predicts the proportion of the testes made up of sperm producing seminiferous tissue and the rate of sperm production (Willett & Ohms 1957, Parker 1982, Møller 1989, Marconato & Shapiro 1996, Scharer et al 2004, Lü pold et al 2009c, Ramm & Stockley 2010, Rowe & Pruett-Jones 2011, males with larger testes are expected to be competitively advantaged when engaging in sperm competition. Consequently, increases in the level of sperm competition are expected to select for increased investment in testicular tissue (Parker & Pizzari 2010).…”

Section: Sperm: Solders In the Battle For Fertilizationmentioning

confidence: 99%

Sperm wars and the evolution of male fertility

Simmons¹,

Fitzpatrick²

2012

Reproduction

300

343

View full text Add to dashboard Cite

Females frequently mate with several males, whose sperm then compete to fertilize available ova. Sperm competition represents a potent selective force that is expected to shape male expenditure on the ejaculate. Here, we review empirical data that illustrate the evolutionary consequences of sperm competition. Sperm competition favors the evolution of increased testes size and sperm production. In some species, males appear capable of adjusting the number of sperm ejaculated, depending on the perceived levels of sperm competition. Selection is also expected to act on sperm form and function, although the evidence for this remains equivocal. Comparative studies suggest that sperm length and swimming speed may increase in response to selection from sperm competition. However, the mechanisms driving this pattern remain unclear. Evidence that sperm length influences sperm swimming speed is mixed and fertilization trials performed across a broad range of species demonstrate inconsistent relationships between sperm form and function. This ambiguity may in part reflect the important role that seminal fluid proteins (sfps) play in affecting sperm function. There is good evidence that sfps are subject to selection from sperm competition, and recent work is pointing to an ability of males to adjust their seminal fluid chemistry in response to sperm competition from rival males. We argue that future research must consider sperm and seminal fluid components of the ejaculate as a functional unity. Research at the genomic level will identify the genes that ultimately control male fertility.

show abstract

Sperm competition and sperm length influence the rate of mammalian spermatogenesis

Cited by 77 publications

References 28 publications

Variation in the molecular clock of primates

Variation in the molecular clock of primates

Female monopolization mediates the relationship between pre- and postcopulatory sexual traits

Sperm wars and the evolution of male fertility

Contact Info

Product

Resources

About