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paco.garcia[at]ebd.csic.es

Sexual selection

Publications filtered by: Sexual selection

Risk-spreading by mating multiply is plausible and requires empirical attention
Garcia-Gonzalez, F., Yasui, Y. & Evans, J.P. 2015 Risk-spreading by mating multiply is plausible and requires empirical attention Proceedings of the Royal Society of London B, 282: 20150866
Transgenerational effects of sexual interactions and sexual conflict: non-sires boost the fecundity of females in the following generation
Garcia-Gonzalez, F. and Dowling, D. K. 2015 Transgenerational effects of sexual interactions and sexual conflict: non-sires boost the fecundity of females in the following generation Biology Letters, 11:20150067
Abstract

The consequences of sexual interactions extend beyond the simple production of offspring. These interactions typically entail direct effects on female fitness, but may also impact the life histories of later generations. Evaluating the cross-generational effects of sexual interactions provides insights into the dynamics of sexual selection and conflict. Such studies can elucidate whether offspring fitness optima diverge across sexes upon heightened levels of sexual interaction among parents. Here, we found that, in Drosophila melanogaster, components of reproductive success in females, but not males, were contingent on the nature of sexual interactions experienced by their mothers. In particular, maternal sexual interactions with non-sires enhanced female fecundity in the following generation. This highlights the importance of non-sire influences of sexual interactions on the expression of offspring life histories.The consequences of sexual interactions extend beyond the simple production of offspring. These interactions typically entail direct effects on female fitness, but may also impact the life histories of later generations. Evaluating the cross-generational effects of sexual interactions provides insights into the dynamics of sexual selection and conflict. Such studies can elucidate whether offspring fitness optima diverge across sexes upon heightened levels of sexual interaction among parents. Here, we found that, in Drosophila melanogaster, components of reproductive success in females, but not males, were contingent on the nature of sexual interactions experienced by their mothers. In particular, maternal sexual interactions with non-sires enhanced female fecundity in the following generation. This highlights the importance of non-sire influences of sexual interactions on the expression of offspring life histories.

Evolutionary change in testes tissue composition among experimental populations of house mice
Firman, R. C., Garcia-Gonzalez, F., Thyer, E., Wheeler, S., Yamin, Z., Yuan, M. and Simmons, L. W. 2015 Evolutionary change in testes tissue composition among experimental populations of house mice Evolution, 69: 848-855
Abstract

Theory assumes that postcopulatory sexual selection favours increased investment in testes size because greater numbers of sperm within the ejaculate increase the chance of success in sperm competition, and larger testes are able to produce more sperm. However, changes in the organization of the testes tissue may also affect sperm production rates. Indeed, recent comparative analyses suggest that sperm competition selects for greater proportions of sperm-producing tissue within the testes. Here, we explicitly test this hypothesis using the powerful technique of experimental evolution. We allowed house mice (Mus domesticus) to evolve via monogamy or polygamy in six replicate populations across 24 generations. We then used histology and image analysis to quantify the proportion of sperm-producing tissue (seminiferous tubules) within the testes of males. Our results show that males that had evolved with sperm competition had testes with a higher proportion of seminiferous tubules compared with males that had evolved under monogamy. Previously, it had been shown that males from the polygamous populations produced greater numbers of sperm in the absence of changes in testes size. We thus provide evidence that sperm competition selects for an increase in the density of sperm-producing tissue, and consequently increased testicular efficiency.

Mating portfolios: bet-hedging, sexual selection and female multiple mating
Garcia-Gonzalez, F., Yasui, Y. and Evans, J. P. 2015 Mating portfolios: bet-hedging, sexual selection and female multiple mating Proceedings of the Royal Society of London B, 282: 20141525
Abstract

Polyandry (female multiple mating) has profound evolutionary and ecological implications. Despite considerable work devoted to understanding why females mate multiply, we currently lack convincing empirical evidence to explain the adaptive value of polyandry. Here we provide a direct test of the controversial idea that bet-hedging functions as a risk-spreading strategy that yields multi-generational fitness benefits to polyandrous females. Unfortunately, testing this hypothesis is far from trivial, and the empirical comparison of the across-generations fitness payoffs of a polyandrous (bet hedger) versus a monandrous (non-bet hedger) strategy has never been accomplished because of numerous experimental constraints presented by most ‘model’ species. In the present study we take advantage of the extraordinary tractability and versatility of a marine broadcast spawning invertebrate to overcome these challenges. We are able to simulate multi-generational (geometric mean) fitness among individual females assigned simultaneously to a polyandrous and monandrous mating strategy. Our approaches, which separate and account for the effects of sexual selection and pure bet-hedging scenarios, reveal that bet-hedging, in addition to sexual selection, can enhance evolutionary fitness in multiply-mated females. In addition to offering a tractable experimental approach for addressing bet-hedging theory, our study provides key insights into the evolutionary ecology of sexual interactions.

Patterns of paternity skew among polyandrous social insects: What can they tell us about the potential for sexual selection?
Jaffé, R., F. Garcia-Gonzalez, S. P. A. den Boer, L. W. Simmons, & B. Baer. 2012 Patterns of paternity skew among polyandrous social insects: What can they tell us about the potential for sexual selection? Evolution, 66:3778-3788
Abstract

Monogamy results in high genetic relatedness among offspring and thus it is generally assumed to be favored by kin selection. Female multiple mating (polyandry) has nevertheless evolved several times in the social Hymenoptera (ants, bees, and wasps), and a substantial amount of work has been conducted to understand its costs and benefits. Relatedness and inclusive fitness benefits are, however, not only influenced by queen mating frequency but also by paternity skew, which is a quantitative measure of paternity biases among the offspring of polyandrous females.We performed a large-scale phylogenetic analysis of paternity skew across polyandrous social Hymenoptera. We found a general and significant negative association between paternity frequency and paternity skew. High paternity skew, which increases relatedness among colony members and thus maximizes inclusive fitness gains, characterized species with low paternity frequency. However, species with highly polyandrous queens had low paternity skew, with paternity equalized among potential sires. Equal paternity shares among fathers are expected to maximize fitness benefits derived from genetic diversity among offspring. We discuss the potential for postcopulatory sexual selection to influence patterns of paternity in social insects, and suggest that sexual selection may have played a key, yet overlooked role in social evolution.

La evolución de la poliandria
Garcia-Gonzalez, F. 2012 La evolución de la poliandria Investigación y Ciencia 429:9-12
Abstract
Durante siglos se ha considerado que la relación sexual dominante en el mundo animal era la monogamia. Sin embargo, en las últimas décadas, la aplicación sistemática de los análisis de paternidad al estudio del comportamiento ha puesto de manifiesto la amplia presencia de otro fenómeno: la poliandria, el apareamiento de una hembra con varios machos en el transcurso de un mismo episodio reproductivo. Si tomamos como ejemplo uno de los iconos tradicionales de la monogamia, las aves que forman parejas estables, descubrimos que las hembras de más del 70 por ciento de las especies de este grupo copulan con otros machos. Y esto no es una excepción: la poliandria es la norma en un gran número de grupos animales. La poliandria comporta una serie de implicaciones evolutivas de gran calibre y, por ello, su estudio atrae la atención de investigadores en todo el mundo. La consecuencia más importante del comportamiento poliándrico se puede ilustrar con un trabajo clásico que estudió el comportamiento sexual de un grupo de macacos a lo largo de ocho años. El macho dominante del clan consumó el 70 por ciento de las cópulas, mientras que el segundo en el orden de jerarquía apenas participó en el 14 por ciento de ellas. En cambio, el número de descendientes engendrado por el macho dominante resultó ser la mitad que el de su subordinado. De ello se desprende que, en los machos, el éxito en el apareamiento no garantiza el éxito en la procreación cuando impera la poliandria.
Experimental coevolution of male and female genital morphology
Simmons L. W. & Garcia-Gonzalez, F. 2011 Experimental coevolution of male and female genital morphology Nature Communications, 2:374
Abstract
Male genitalia typically exhibit patterns of rapid and divergent evolution, and there is now considerable evidence that sexual selection is an important driver of these patterns of phenotypic variation. Female genitalia have been less well studied, and are generally thought to be relatively invariant. Here we use experimental evolution to show that sexual selection drives the correlated evolution of female and male genital morphology in the scarabaeine dung beetle Onthophagus taurus. Moreover, we use quantitative genetic analyses to provide a rare insight into the genetic architecture underlying morphological variation in female genital morphology, and uncover evidence of the genetic covariation with male genital morphology that is expected to arise under persistent sexual selection.
Fertilization success and the estimation of genetic variance in sperm competitiveness
Garcia-Gonzalez, F. & Evans, J. P. 2011 Fertilization success and the estimation of genetic variance in sperm competitiveness Evolution, 65: 746-756
Abstract
A key question in sexual selection is whether the ability of males to fertilize eggs under sperm competition exhibits heritable genetic variation. Addressing this question poses a significant problem, however, because a male’s ability to win fertilizations ultimately depends on the competitive ability of rival males. Attempts to partition genetic variance in sperm competitiveness, as estimated from measures of fertilization success, must therefore account for stochastic effects due to the random sampling of rival sperm competitors. In this contribution, we suggest a practical solution to this problem. We advocate the use of simple crossclassified breeding designs for partitioning sources of genetic variance in sperm competitiveness and fertilization success and show how these designs can be used to avoid stochastic effects due to the random sampling of rival sperm competitors. We illustrate the utility of these approaches by simulating various scenarios for estimating genetic parameters in sperm competiveness, and show that the probability of detecting additive genetic variance in this trait is restored when stochastic effects due to the random sampling of rival sperm competitors are controlled. Our findings have important implications for the study of the evolutionary maintenance of polyandry.
Sexual Selection and Experimental Evolution
Garcia-Gonzalez, F. & Simmons, L. W. 2011 Sexual Selection and Experimental Evolution Encyclopedia of Life Sciences (ELS). John Wiley & Sons, Ltd. Chichester. DOI:10.1002/9780470015902.a0022859.
Abstract
Sexual selection is a potent force shaping multiple aspects of the interaction between the sexes, including the characters underlying reproductive success and sexual conflict, and may play an important role in determining the viability of populations. Experimental evolution is a methodological approach in which researchers either act as selective agents or establish the selective pressures operating on individuals to investigate changes in traits across generations and the genetic underpinning of these changes. Experimental evolution replicates the evolutionary process under controlled conditions and, by doing so, offers exceptional insights into the role of variation, selection and adaptation in evolution. Applied to the study of pre-copulatory (before mating) and postcopulatory (after mating) sexual selection, experimental evolution proves critical to understand the evolutionary consequences of male–malecompetition and femalemate choice, and the repercussions of concurrent or divergent interests between the sexes in regard to reproduction.
Good genes and sexual selection in dung beetles (Onthophagus taurus): Genetic variance in egg-to-adult and adult viability
Garcia-Gonzalez, F. & Simmons, L. W. 2011 Good genes and sexual selection in dung beetles (Onthophagus taurus): Genetic variance in egg-to-adult and adult viability PLoS ONE, 6:e16233
Abstract
Whether species exhibit significant heritable variation in fitness is central for sexual selection. According to good genes models there must be genetic variation in males leading to variation in offspring fitness if females are to obtain genetic benefits from exercising mate preferences, or by mating multiply. However, sexual selection based on genetic benefits is controversial, and there is limited unambiguous support for the notion that choosy or polyandrous females can increase the chances of producing offspring with high viability. Here we examine the levels of additive genetic variance in two fitness components in the dung beetle Onthophagus taurus. We found significant sire effects on egg-to-adult viability and on son, but not daughter, survival to sexual maturity, as well as moderate coefficients of additive variance in these traits. Moreover, we do not find evidence for sexual antagonism influencing genetic variation for fitness. Our results are consistent with good genes sexual selection, and suggest that both pre- and postcopulatory mate choice, and male competition could provide indirect benefits to females.

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