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Experimental evolution

Publications filtered by: Experimental evolution

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.

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.
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.
Seen one seen them all? More to genitalia than meets the eye
Simmons, L. W. & Garcia-Gonzalez, F. 2011 Seen one seen them all? More to genitalia than meets the eye The Conversation
Experimental evolution: life in the fast line
Garcia-Gonzalez, F. & Simmons, L. W. 2011 Experimental evolution: life in the fast line The Conversation
Evolutionary response to sexual selection in male genital morphology
Simmons, L. W., House, C. M., Hunt, J. & Garcia-Gonzalez, F. 2009 Evolutionary response to sexual selection in male genital morphology Current Biology, 19: 1442-1446
Abstract

Male genital morphology is characterized by two striking and general patterns of morphological variation: rapid evolutionary divergence in shape and complexity, and relatively low scaling relationships with body size. These patterns of variation have been ascribed to the action of sexual selection. Among species, monogamous taxa tend to have relatively less complex male genital morphology than do polygamous taxa. However, although variation in male genital morphology can be associated with variation in mating and fertilization success, there is no direct evidence that sexual selection generates the evolutionary changes in male genital shape that underlie observed macroevolutionary patterns. Moreover, the hypothesis that sexual selection acts to reduce the scaling relationship between body and genital size is based entirely on the theoretical argument that male genitalia should be selected to provide an appropriate mechanical and/or stimulatory fit to the most commonly encountered female genitalia. Here, using the dung beetle Onthophagus taurus, we combine the power of experimental evolution with multivariate selection and quantitative genetic analyses to provide the most comprehensive evidence available of the form and evolutionary consequences of sexual selection acting on male genital morphology.

Evolución en acción: estudios de evolución experimental en el contexto de la selección sexual. In: Dopazo, H. and Navarro, A. (Eds). Adaptación y Evolución. 150 años después del Origen de las Especies.
Garcia-Gonzalez, F. 2009 Evolución en acción: estudios de evolución experimental en el contexto de la selección sexual. In: Dopazo, H. and Navarro, A. (Eds). Adaptación y Evolución. 150 años después del Origen de las Especies Sociedad Española de Biología Evolutiva-Obrapropia S. L., Valencia.
Abstract

Los estudios de evolución experimental constituyen una herramienta de extrema utilidad para comprender los procesos evolutivos a nivel intra-específico. Este artículo expone, a grandes rasgos, en qué consiste la evolución experimental y qué información ofrece. Se resalta el caso particular de estudios que utilizan esta aproximación metodológica para avanzar en el conocimiento de la selección sexual y de sus consecuencias evolutivas. Se muestra con algunos ejemplos cómo los estudios de evolución experimental contribuyen de manera significativa a mejorar la comprensión de la evolución de caracteres que determinan el éxito en el apareamiento y la fecundación, o de las diferencias entre los sexos.

Evolutionary reduction in testes size and competitive fertilization success in response to the experimental removal of sexual selection in dung beetles
Simmons, L. W. & Garcia-Gonzalez, F. 2008 Evolutionary reduction in testes size and competitive fertilization success in response to the experimental removal of sexual selection in dung beetles Evolution, 62:2580-2591
Abstract
Sexual selection is thought to favor the evolution of secondary sexual traits in males that contribute to mating success. In species where females mate with more than one male, sexual selection also continues after copulation in the form of sperm competition and cryptic female choice. Theory suggests that sperm competition should favor traits such as testes size and sperm production that increase a male’s competitive fertilization success. Studies of experimental evolution offer a powerful approach for assessing evolutionary responses to variation in sexual selection pressures. Here we removed sexual selection by enforcing monogamy on replicate lines of a naturally polygamous horned beetle, Onthophagus taurus, and monitoring male investment in their testes for 21 generations. Testes size decreased in monogamous lines relative to lines in which sexual selection was allowed to continue. Differences in testes size were dependent on selection history and not breeding regime. Males from polygamous lines also had a competitive fertilization advantage when in sperm competition with males from monogamous lines. Females from polygamous lines produced sons in better condition, and those from monogamous lines increased their sons condition by mating polygamously. Rather than being costly for females, multiple mating appears to provide females with direct and/or indirect benefits. Neither body size nor horn size diverged between our monogamous and polygamous lines. Our data show that sperm competition does drive the evolution of testes size in onthophagine beetles, and provide general support for sperm competition theory.