Sexual Selection

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Sexual Selection 9 March 2009 Evolution and Natural Selection Evolution - Changes in gene frequencies over time Natural Selection – “survival of the fittest ” Pepper Moth Story Sexual Selection The evolution of extravagant characters (sexual selection) arises from differences in reproductive success caused by competition over mates Darwin (1868 and 1871) Mechanisms of competition over mates 1) Scrambles 2) Endurance Rivalry 3) Contests 4) MtMate ChiChoice 5) Sperm competition Ma les are usua lly th e sex th at compet es b ecause f emal es normall y invest more into reproduction. Scrambles Copulat ions are regul ated b y th e abili ty of th e mal e to fi nd a mate. Males of species that breed through scrambles often have enlarged sensoryyg organs for faster location of females Females release phermones tha t are d e tect ed b y h ai rs on the males antennae. Endurance rivalry The most persistent males are the most successful breeders Extended effort into breeding activity shows that the animal is in good physical condition and is an efficient forager. Contests -Fights between males for the opportunity to mate. -Male traits associated with fighting ability are referred to as “”“armaments.” Contests cont. Contests can be for direct access to females or to control a better territory. Mate choice Females choose a mate based on certain characters of the male These characters are referred to as ornaments. Ornaments can also function in contests as well as in mate choice. Mechanisms for female preference -Fisher’s Runaway Process -ZhZahav i’Hi’s Han dicap P Pirinci ilple -Sensory Exploitation (Ryan) Runaway process Female choice and male trait have a genetic correlation Male traits are limited by natural selection Irish Elk Common Peafowl Handicap principle Females select males with the most elaborate displays or most conspicuous ornaments because it signals high quality Sensory exploitation (Ryan) Females have a pre-existing bias for a particular trait and the males exploit that bias Sperm competition Mate guarding, sequestering, frequent copulations, production of mating plugs Examples: Primates, cuddlefish Review Sexual Selection mechanisms for competition over mates 1. Scrambles 2. Endurance Rivalry 3. Contests 4. Mate Choice – mechanisms for female preference 1. Runaway process 2. Handicap principle 3. Sensoryyp exploitaion 5. Sperm Competition.

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Sexual Selection, Sex Roles, and Sexual Conflict
Downloaded from http://cshperspectives.cshlp.org/ on October 1, 2021 - Published by Cold Spring Harbor Laboratory Press The Sexual Cascade and the Rise of Pre-Ejaculatory (Darwinian) Sexual Selection, Sex Roles, and Sexual Conflict Geoff A. Parker Department of Evolution, Ecology and Behaviour, Institute of Integrative Biology, University of Liverpool, Liverpool L69 7ZB, United Kingdom Correspondence: [email protected] After brief historic overviews of sexual selection and sexual conflict, I argue that pre-ejacu- latory sexual selection (the form of sexual selection discussed by Darwin) arose at a late stage in an inevitable succession of transitions flowing from the early evolution of syngamy to the evolution of copulation and sex roles. If certain conditions were met, this “sexual cascade” progressed inevitably, if not, sexual strategy remained fixed at a given stage. Prolonged evolutionary history of intense sperm competition/selection under external fertilization preceded the rise of advanced mobility, which generated pre-ejaculatory sexual selection, followed on land by internal fertilization and reduced sperm competition in the form of postcopulatory sexual selection. I develop a prospective model of the early evolution of mobility, which, as Darwin realized, was the catalyst for pre-ejaculatory sexual selection. Stages in the cascade should be regarded as consequential rather than separate phenomena and, as such, invalidate much current opposition to Darwin–Bateman sex roles. Potential for sexual conflict occurs throughout, greatly increasing later in the cascade, reaching its peak under precopulatory sexual selection when sex roles become highly differentiated. exual selection and sexual conflict are vast changed through evolutionary time, from Sfields in evolutionary biology; when possi- mostly gamete competition in early unicellu- ble, here, I refer to reviews.
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Another Way of Being Anisogamous in Drosophila Subgenus
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Biol B242 - Coevolution
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Sex-Specific Spawning Behavior and Its Consequences in an External Fertilizer
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Mating Preferences Might Evolve by Natural Selection. If Mating Mate
A GENERAL MODEL OF SEXUAL AND NATURAL SELECTION P. O'DONALD Department of Zoology, University College of North Wales, bangor Received28.xii.66 1.INTRODUCTION FISHERin The Genetical Theory of JVatural Selection (1930) described how mating preferences might evolve by natural selection. If mating behaviour varies among different genotypes, some individuals may have an hereditary disposition to mate with others having particular characteristics. Usually of course it is the females who choose the males and their choice is determined by the likelihood that the males' display will release their mating responses. If some females prefer to mate with those males that have characteristics advantageous in natural selection, then the genotypes that determine such matings will also be selected: the offspring will carry both the advantageous geno- types and the genotypes of the mating preference. Once the mating preference is established, it will itself add to the selective advantage of the preferred genotypes: a "runaway process" as Fisher called it develops. In a paper in Heredity (1963) I described a mathematical model of this type of selection. In the simplest case two loci must be involved: one locus determines the preferred character and the other the mating preference. If there are only two alleles segregating at each locus, ten different genotypes can occur if the loci are linked and nine if they are not. If they are sex-linked, there are i possible genotypes. I derived finite difference equations giving the frequencies of the genotypes in terms of parameters describing the degree of dominance of the preferred genotypes and the recombination fractions of the loci.
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Sperm Competition Enhances Functional Capacity of Mammalian
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Mate Choice | Principles of Biology from Nature Education
contents Principles of Biology 171 Mate Choice Reproduction underlies many animal behaviors. The greater sage grouse (Centrocercus urophasianus). Female sage grouse evaluate males as sexual partners on the basis of the feather ornaments and the males' elaborate displays. Stephen J. Krasemann/Science Source. Topics Covered in this Module Mating as a Risky Behavior Major Objectives of this Module Describe factors associated with specific patterns of mating and life history strategies of specific mating patterns. Describe how genetics contributes to behavioral phenotypes such as mating. Describe the selection factors influencing behaviors like mate choice. page 882 of 989 3 pages left in this module contents Principles of Biology 171 Mate Choice Mating as a Risky Behavior Different species have different mating patterns. Different species have evolved a range of mating behaviors that vary in the number of individuals involved and the length of time over which their relationships last. The most open type of relationship is promiscuity, in which all members of a community can mate with each other. Within a promiscuous species, an animal of either gender may mate with any other male or female. No permanent relationships develop between mates, and offspring cannot be certain of the identity of their fathers. Promiscuous behavior is common in bonobos (Pan paniscus), as well as their close relatives, the chimpanzee (P. troglodytes). Bonobos also engage in sexual activity for activities other than reproduction: to greet other members of the community, to release social tensions, and to resolve conflicts. Test Yourself How might promiscuous behavior provide an evolutionary advantage for males? Submit Some animals demonstrate polygamous relationships, in which a single individual of one gender mates with multiple individuals of the opposite gender.
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Human Sexual Selection
Available online at www.sciencedirect.com ScienceDirect Human sexual selection David Puts Sexual selection favors traits that aid in competition over Here, I review evidence, focusing on recent ﬁndings, mates. Widespread monogamous mating, biparental care, regarding the strength and forms of sexual selection moderate body size sexual dimorphism, and low canine tooth operating over human evolution and consider how sexual dimorphism suggest modest sexual selection operating over selection has shaped human psychology, including psy- human evolution, but other evidence indicates that sexual chological sex differences. selection has actually been comparatively strong. Ancestral men probably competed for mates mainly by excluding The strength of human sexual selection competitors by force or threat, and women probably competed Some evidence suggests that sexual selection has been primarily by attracting mates. These and other forms of sexual relatively weak in humans. Although sexual dimorphisms selection shaped human anatomy and psychology, including in anatomy and behavior may arise from other selective some psychological sex differences. forces, the presence of sexually dimorphic ornamentation, Address weaponry, courtship displays, or intrasexual competition Department of Anthropology and Center for Brain, Behavior and indicates a history of sexual selection [3]. However, men’s Cognition, Pennsylvania State University, University Park, PA 16802, 15–20% greater body mass than women’s is comparable to USA primate species with a modest degree of mating competi- tion among males, and humans lack the canine tooth Corresponding author: Puts, David ([email protected]) dimorphism characteristic of many primates with intense male competition for mates [4]. Moreover, humans exhibit Current Opinion in Psychology 2015, 7:28–32 biparental care and social monogamy, which tend to occur This review comes from a themed issue on Evolutionary psychology in species with low levels of male mating competition [5].
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Factors Influencing the Diversification of Mating Behavior of Animals
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Sperm Competition and Sex Change: a Comparative Analysis Across Fishes
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