DOCSLIB.ORG

Sexual Dimorphism Sexual Selection

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Sexual Dimorphism Sexual Selection Sexual dimorphism Sexual selection Is sexual selection different from natural selection? Darwin saw them as distinct - only sexual selection could produce traits that compromise survival The basic principle – selection favors whatever gets more genes into the next generation In sexual selection, fitness is measured relative to members of the same sex Two kinds of sexual selection Intrasexual selection – mating success determined by within-sex interactions e.g., male-male combat Intersexual selection – mating success determined by between-sex interactions e.g., female choice of males (also referred to as epigamic selection) Mating systems Mating systems influence sexual selection Strength of sexual selection Variance in mating success All males have Some males = 0 mates Most males = 0 mates same mating Some males = 1 mate One male = 8 mates success = 1 mate Some males = 2 mates Monogamy Moderate Polygyny Strong Polygyny The peacock’s tail Extravagant male ornaments The peacock’s tail greatly impairs his mobility…how could such a trait evolve? Why a theory of sexual selection? Darwin needed a theory to explain the many extravagant traits that seem to reduce survival e.g. the peacock’s tail His rationale, that conspicuous male displays persist and grow ever more conspicuous because females prefer them, never fully explained the benefit of choosing the brightest or loudest. Darwin "Thus a struggle produced by sexual selection in males exists not because of the struggle for existence, but because it give the males that possess it an advantage over other males in the competition for mates.“ Decrease in fitness (due to trait) compensated by increase in mating success What are Females choosing? 1) Males who possess good genes 2) Males who provide resources 3) Males whose signal matches a preexisting sensory bias 4) Males who are sexy and will thus produce sexy sons who will also have success in mating Parasitic Theory of Sexual Selection & Bright Coloration of Males "General good health and freedom from parasites are often strikingly indicated in plumage and fur, particularly when these are bright rather than dull and cryptic." Hamilton & Zuk • females should choose parasite-free males • why? pass on resistant genes to offspring • bright colors = sign of health •If disease resistance is heritable, females are making sure they have healthy offspring if they choose such healthy looking males • prediction: relatively more brightly colored males in more parasitized species Like a personal ad proclaiming: "Tall, good looking, disease-free," brightly colored male animals may be advertising something of importance to their prospective mates. Should the female assume the gaudiest male has parasite-resistance genes that will benefit her offspring? Or that she simply won't pick up bugs from the guy? • decreases maneuverability & increases visibility to predators • why does it exist? why is it not eliminated? • natural selection cannot explain why traits that decrease survival exist Many sexually dimorphic male display traits seem costly. Costly displays will evolve if females actively choose males with brighter or more exaggerated traits. GOOD GENES MODEL ELABORATED MALE TRAITS MAY BE INDICATORS OF HERITABLE GENETIC QUALITY (I.E. FITNESS). Some males may have a heritable trait that reduces viability. Only males with “Good Genes” can survive despite the handicap. Females that mate with these males will have offspring with higher fitness Hypotheses for male ornaments Fisher’s “runaway” hypothesis Mate choice originally evolved to facilitate adaptive choice for traits conferring a survival advantage Once female preference evolved, any genes that conferred survival advantage but compromised attractiveness would not be passed on because surviving males would fail to mate The female preference genes will “hitchhike” onto the successful male genes. Zahavi’s “handicap” hypotheses Extravagant male traits are costly to develop and maintain Choosing a mate with “good genes” requires an honest signal of genetic quality Only males in good condition (those with good genes) will be able to fully develop and maintain an ornament Zahavi’s handicap hypothesis Some candidate “handicaps” Note that the handicap itself need not be heritable…it need only provide a reliable index of fitness, and fitness must be heritable Traits that encumber the owner are physiologically costly (exertion in flight) as well as being more expensive to develop Asymmetry is indicative of developmental instability and possibly “bad genes”. Symmetry Bright color honestly signals is chosen in some species immunocompetence and parasite/disease resistance HANDICAP PRINCIPLE . The bigger the handicap, the higher the genetic quality of the male carrying the trait. Female choice evolves and the handicap spreads and becomes elaborated. Assumes the superior quality is heritable . This is an example of an honest signal since there is a true cost to the elaborated trait that prevents “cheaters”. What does having a tail three times your body length have to do with good genes? Differential Costs of a Secondary Sexual Character: An Experimental Test of the Handicap Principle Moller and de Lope 1994 • Manipulated tail lengths in males: – Shortened by 20mm – Extended by 20mm – Cut & Glued (treatment control) – No manipulation (control) • Survival rate: return rates to breeding sites MATING SUCCESS RELATED TO TAIL LENGTH “Mock” altered Unaltered Barn swallow Experimental manipulation of tail length Males with elongated tails: 1. Obtain mates more quickly 2. Have greater reproductive success 3. Experience a cost in tail size the following year Are these traits costly? In the year after Moller’s (1988) experiment on barn swallows, males with experimentally elongated tails grew significantly shorter tails than the previous year What does a long tail indicate? Therefore: 1) trait is costly 2) tail maintained by female choice • lower loads of blood-sucking mites on males with larger tails • placed 50 mites/nest of various males • later date: offspring of males with longer tails had lower mite loads Therefore: genetic basis to resistance (good genes passed on!) Males with longer tails fathered offspring with lower parasite loads Parasite load of offspring Parasite load of offspring measured in biological measured in a foster parent’s nest parent’s nest Runaway Model: Trait initially advantageous Preferences and trait become genetically correlated (♂ expressed, ♀ preference) Requires heritability of trait and preference, trait cannot be too expensive. Zahavi ‘s Handicap principle Traits not chosen despite being costly, but BECAUSE they are costly they must have negative effects on fitness, so only males of the highest genetic quality can successfully develop the trait (i.e., the trait is costly to maintain) Good genes model: ornaments are a sign of good genes, and have a cost to keep the displayer honest. Traits reveal male condition: females select males of the highest genetic quality Conditional traits- expressed by high quality males Viability: expressed by all males but tend to kill off low quality males Problem: what maintains genetic variation for goodness? Would everyone not soon have the good genes and therefore no variability for females to assess?? Hamilton-Zuk hypothesis: (the red queen returns) Females prefer resistant/showy males Correlation between quality (resistance) and the trait, or negative correlation between parasite load and trait Heritable variation in resistance (often difficult to prove) Parasite load reduces host viability Within a species: guppy infestations lowers male brightness, reduces sexual displays, females prefer bright males. Heritable – unknown If this is true: there should be a correlation between parasite load Can development of these traits be condition-dependent? Many secondary sexual traits do develop in proportion to male condition: antler size (reduced by starvation in red deer) orange spots in guppies affected by carotenoid content of diet—may reflect food-finding ability tail length in swallows and widowbirds horn size in beetles—may depend on larval nutrition hormone levels that regulate secondary sexual traits—sensitive to nutrition Some indirect benefits Carotenoid Modulation of Immune Function and Sexual Attractiveness in Zebra Finches Blount et al. One hypothesis for female choice predicts that availability of carotenoid pigments is a potentially limiting factor for both ornament expression and immune function. Males that can afford to produce more elaborate carotenoid-dependent displays must be healthier individuals with superior immunocompetence. Manipulation of dietary carotenoid supply invokes parallel changes in cell-mediated immune function and sexual attractiveness in male zebra finches (Taeniopygia guttata). Experimental Group Control Group SCIENCE, April 4, 2003 Plumage brightness in the house finch: condition-dependent Plumage color may also have a genetic component: positive correlation between plumage brightness of father and plumage brightness of sons Brightly colored plumage—reliable indicator of male parental effort; perhaps also an indicator of genetic quality? Males returning to the nesting grounds more brightly colored than the males that did not return— plumage indicates viability? Females who prefer most extreme traits will mate with males with most resistance to parasites: offspring will therefore have high resistance to parasites as well Distinguishing between runaway sexual selection and “good genes” hypotheses Necessary condition
Load more

Recommended publications
  • Quantifying Male Attractiveness Nationsbased on Values Andrewards
    Received 28October 2002 Accepted 13March 2003 Publishedonline 25 July 2003 Quantifyingmale attractivene ss JohnM. McNamara 1* ,AlasdairI. Houston 2,Miguel Marques dosSantos 1, Hanna Kokko3† and RobBrooks 4 1Departmentof Mathematics, University ofBristol, University Walk,Bristol BS8 1TW, UK 2Schoolof Biological Sciences, University ofBristol, Woodland Road, Bristol BS8 1GU, UK 3Division ofEnvironmentaland EvolutionaryBiology, Institute ofBiomedical and Life Sciences, University ofGlasgow, GlasgowG12 8QQ, UK 4Schoolof Biological Earth and EnvironmentalSciences, TheUniversity ofNew SouthWales, Sydney, NSW 2052,Australia Geneticmodels of sexual selectionare concernedwith adynamic processin which female preferenceand male trait values coevolve.We present a rigorous methodfor characterizing evolutionary endpointsof this processin phenotypic terms.In ourphenotypic characterization themate-choice strategy offemale popu- lation members determineshow attractive femalesshould find each male, anda population is evol- utionarily stable if population members are actually behaving in this way.This provides ajustificationof phenotypic explanations ofsexual selectionand the insights into sexual selectionthat they provide. Fur- thermore, thephenotypic approach also has enormousadvantages over ageneticapproach whencomput- ing evolutionarily stable mate-choicestrategies, especially whenstrategies are allowed tobecomplex time- dependentpreference rules. For simplicity andclarity ouranalysis dealswith haploid mate-choicegenetics anda male trait that is inherited
    [Show full text]
  • Evolution of Female Multiple Mating: a Quantitative Model of the “Sexually Selected Sperm” Hypothesis
    ORIGINAL ARTICLE doi:10.1111/evo.12550 Evolution of female multiple mating: A quantitative model of the “sexually selected sperm” hypothesis Greta Bocedi1,2 and Jane M. Reid1 1Institute of Biological and Environmental Sciences, University of Aberdeen, Zoology Building, Tillydrone Avenue, Aberdeen AB24 2TZ, United Kingdom 2E-mail: [email protected] Received June 5, 2014 Accepted October 1, 2014 Explaining the evolution and maintenance of polyandry remains a key challenge in evolutionary ecology. One appealing explana- tion is the sexually selected sperm (SSS) hypothesis, which proposes that polyandry evolves due to indirect selection stemming from positive genetic covariance with male fertilization efficiency, and hence with a male’s success in postcopulatory competition for paternity. However, the SSS hypothesis relies on verbal analogy with “sexy-son” models explaining coevolution of female preferences for male displays, and explicit models that validate the basic SSS principle are surprisingly lacking. We developed analogous genetically explicit individual-based models describing the SSS and “sexy-son” processes. We show that the analogy between the two is only partly valid, such that the genetic correlation arising between polyandry and fertilization efficiency is generally smaller than that arising between preference and display, resulting in less reliable coevolution. Importantly, indirect selection was too weak to cause polyandry to evolve in the presence of negative direct selection. Negatively biased mutations on fertilization efficiency did not generally rescue runaway evolution of polyandry unless realized fertilization was highly skewed toward a single male, and coevolution was even weaker given random mating order effects on fertilization. Our models suggest that the SSS process is, on its own, unlikely to generally explain the evolution of polyandry.
    [Show full text]
  • Ornamentation, Behavior, and Maternal Effects in the Female Northern Cardinal
    The University of Southern Mississippi The Aquila Digital Community Master's Theses Summer 8-2011 Ornamentation, Behavior, and Maternal Effects in the Female Northern Cardinal Caitlin Winters University of Southern Mississippi Follow this and additional works at: https://aquila.usm.edu/masters_theses Part of the Biology Commons, and the Ornithology Commons Recommended Citation Winters, Caitlin, "Ornamentation, Behavior, and Maternal Effects in the Female Northern Cardinal" (2011). Master's Theses. 240. https://aquila.usm.edu/masters_theses/240 This Masters Thesis is brought to you for free and open access by The Aquila Digital Community. It has been accepted for inclusion in Master's Theses by an authorized administrator of The Aquila Digital Community. For more information, please contact [email protected]. The University of Southern Mississippi ORNAMENTATION, BEHAVIOR, AND MATERNAL EFFECTS IN THE FEMALE NORTHERN CARDINAL by Caitlin Winters A Thesis Submitted to the Graduate School of The University of Southern Mississippi in Partial Fulfillment of the Requirements for the Degree of Master of Science Approved: _Jodie M. Jawor_____________________ Director _Frank R. Moore_____________________ _Robert H. Diehl_____________________ _Susan A. Siltanen____________________ Dean of the Graduate School August 2011 ABSTRACT ORNAMENTATION, BEHAVIOR, AND MATERNAL EFFECTS IN THE FEMALE NORTHERN CARDINAL by Caitlin Winters August 2011 This study seeks to understand the relationship between ornamentation, maternal effects, and behavior in the female Northern Cardinal (Cardinalis cardinalis). Female birds possess ornaments that indicate a number of important known aspects of quality and are usually costly to maintain. However, the extent to which female specific traits, such as maternal effects, are indicated is less clear. It is predicted by the Good Parent Hypothesis that this information should be displayed through intraspecific signal communication.
    [Show full text]
  • The Evolution of Sexual Dimorphism: Understanding Mechanisms of Sexual Shape Differences
    Chapter 1 The Evolution of Sexual Dimorphism: Understanding Mechanisms of Sexual Shape Differences Chelsea M. Berns Additional information is available at the end of the chapter http://dx.doi.org/10.5772/55154 1. Introduction Understanding the origin of biodiversity has been a major focus in evolutionary and ecological biology for well over a century and several patterns and mechanisms have been proposed to explain this diversity. Particularly intriguing is the pattern of sexual dimorphism, in which males and females of the same species differ in some trait. Sexual dimorphism (SD) is a pattern that is seen throughout the animal kingdom and is exhibited in a myriad of ways. For example, differences between the sexes in coloration are common in many organisms [1] ranging from poeciliid fishes [2] to dragon flies [3] to eclectus parrots (see Figure 1). A B Figure 1. A) Male Eclectus (© Stijn De Win/Birding2asia) B) Female Eclectus (© James Eaton/Birdtour Asia) © 2013 Berns, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 2 Sexual Dimorphism Sexual dimorphism is also exhibited in ornamentation, such as the horns of dung beetles [4], the antlers of cervids [5], and the tail of peacocks [6]. Many species also exhibit sexual differences in foraging behavior such as the Russian agamid lizard [7], and parental behavior and territoriality can be dimorphic in species such as hummingbirds [8, 9].
    [Show full text]
  • HANDBOOK of PSYCHOLOGY: VOLUME 1, HISTORY of PSYCHOLOGY
    HANDBOOK of PSYCHOLOGY: VOLUME 1, HISTORY OF PSYCHOLOGY Donald K. Freedheim Irving B. Weiner John Wiley & Sons, Inc. HANDBOOK of PSYCHOLOGY HANDBOOK of PSYCHOLOGY VOLUME 1 HISTORY OF PSYCHOLOGY Donald K. Freedheim Volume Editor Irving B. Weiner Editor-in-Chief John Wiley & Sons, Inc. This book is printed on acid-free paper. ➇ Copyright © 2003 by John Wiley & Sons, Inc., Hoboken, New Jersey. All rights reserved. Published simultaneously in Canada. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise, except as permitted under Section 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax (978) 750-4470, or on the web at www.copyright.com. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, (201) 748-6011, fax (201) 748-6008, e-mail: [email protected]. Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives or written sales materials.
    [Show full text]
  • Good Resources – Direct Benefits Good Genes – Indirect Benefits  “Sexy Son” Hypothesis (Fisher)  “Handicap Hypothesis” (Zahavi) Good Genes for Sons, Daughters
    Why are females choosy? Good resources – direct benefits Good genes – indirect benefits “Sexy son” hypothesis (Fisher) “Handicap hypothesis” (Zahavi) Good genes for sons, daughters Good resources courtship feeding parental care, protection fanning eggs good nesting site, territory Good resources Nuptial gifts and copulation time Nuptial gifts Scorpion fly 1 Resources from males can tip the scales of relative investment Mormon cricket males give over 25% body weight in their spermatophore “Ultimate” nuptial gift Why does a spider female kill and eat her mate? Why does a praying mantis eat her mate’s head? Survival is just one strategy to transmit genes. When she eats him, she makes more eggs bearing his genes. His future reproductive chances are low “Sexy son” hypothesis Fisher 1930 – A strictly genetic theory Females with preexisting sensory bias Males w/ this trait are selected, females with the preference are selected Trait might provide nothing beyond mating success The parents Trait A Preference A Trait A Their offspring Preference A 2 “Sexy son” hypothesis Stalk-eyed flies (also stickleback ex. in text) 2 genetic strains were developed: males with short vs. long eye stalks. Selection on males. Females of either strain preferred males from their own strain. Stalk-eyed fly “Sexy son” hypothesis This hypothesis predicts a ‘runaway’ effect When does it stop? Handicap hypothesis Display can be indicator of health (choice based on ‘honest signal’ that is hard to fake) (Zahavi 1975) 3 Handicap hypothesis External features, behavior can indicate general health Comb and tail length changes with infection Guppy females choose males who closely inspect predators Handicap hypothesis Peacock chick growth and survival is linked to ‘eyespot’ size.
    [Show full text]
  • Sexual Selection
    SEXUAL SELECTION What I have called Sexual Selection…depends not on a struggle for existence in relation to other organic beings or to external conditions, but on a struggle between individuals of one sex, generally the males for the possession of the other sex… When the males and females…have the same general habits but differ in structure, colour, or ornament, such differences have been mainly caused by sexual selection. Darwin, The Origin Of Species SEXUAL SELECTION . A special form of selection that accounts for many elaborated traits and behaviors in organisms. Arises from differences in the ability to find and mate with members of the opposite sex. Only occurs when access to one or the other sex is limiting, i. e., when there is competition for mates or offspring. 1 Sexual selection is non-random variance in reproductive success. Two forms of sexual selection: . Intrasexual selection: direct competition for mates between members of the same sex, usually male-male competition. Intersexual selection: differences in attractiveness to the opposite sex, usually non-random mate choice by females. The form of Sexual Selection is directly related to the relative investment in offspring production. The sex that invests more in offspring production has fewer reproductive opportunities. As a result they, . Should be more discriminating (choosier). Become a limiting resource for the opposite sex. ANISOGAMY- Differential investment in reproduction FEMALES: Sex that produces few, well-provisioned gametes (eggs) MALES: Sex that produces many, “cheap” gametes (sperm) 2 Limitations on reproductive success differ for the sexes • Females are limited by fecundity • Males are limited by the number of mates they can obtain Elephant Seals .
    [Show full text]
  • Hippocampus Zosterae) As Threatened Or Endangered Under the Endangered Species Act
    BEFORE THE SECRETARY OF COMMERCE © Jeff Jeffords, www.divegallery.com PETITION TO LIST THE DWARF SEAHORSE (HIPPOCAMPUS ZOSTERAE) AS THREATENED OR ENDANGERED UNDER THE ENDANGERED SPECIES ACT CENTER FOR BIOLOGICAL DIVERSITY NOTICE OF PETITION Mr. Gary F. Locke Secretary of Commerce U.S. Department of Commerce 1401 Constitution Avenue, NW, Rm. 5516 Washington, D.C. 20230 Email: [email protected] Mr. Eric Schwaab Assistant Administrator for Fisheries National Oceanographic and Atmospheric Administration 1315 East-West Highway Silver Spring, MD 20910 Email: [email protected] Dr. Roy E. Crabtree Administrator, Southeast Region National Marine Fisheries Service 263 13th Avenue South St. Petersburg, FL 33701 Email: [email protected] Date: this 6th day of April, 2011 Pursuant to section 4(b) of the Endangered Species Act (“ESA”), 16 U.S.C. § 1533(b), section 553(3) of the Administrative Procedure Act, 5 U.S.C. § 553(e), and 50 C.F.R. § 424.14(a), the Center for Biological Diversity (“Center”), Tierra Curry and Noah Greenwald hereby petition the Secretary of Commerce, through the National Marine Fisheries Service (“NMFS”), to list the dwarf seahorse (Hippocampus zosterae) as a threatened or endangered species under the ESA, 16 U.S.C. §§ 1531 et seq. The Center is a non-profit, public interest environmental organization dedicated to the protection of imperiled species and their habitats through science, policy, and environmental law. The Center has 320,000 members and online activists throughout the United States. NMFS has jurisdiction over this Petition. This Petition sets in motion a specific process, placing definite response requirements on NMFS.
    [Show full text]
  • Female Mate Selection in Terms of Monetary Resources and Number of Children
    Modern Psychological Studies Volume 19 Number 1 Article 6 2013 What a girl wants: female mate selection in terms of monetary resources and number of children Stefanit Tucker Yale University Follow this and additional works at: https://scholar.utc.edu/mps Part of the Psychology Commons Recommended Citation Tucker, Stefanit (2013) "What a girl wants: female mate selection in terms of monetary resources and number of children," Modern Psychological Studies: Vol. 19 : No. 1 , Article 6. Available at: https://scholar.utc.edu/mps/vol19/iss1/6 This articles is brought to you for free and open access by the Journals, Magazines, and Newsletters at UTC Scholar. It has been accepted for inclusion in Modern Psychological Studies by an authorized editor of UTC Scholar. For more information, please contact [email protected]. MPS I Female Mate Selection I Tucker I Pg. 31-38 What a Girl Wants: Female Mate Selection in Terms of Monetary Resources and Number of Children Sefanit Tucker Yale University Abstract Several evolutionary theories provide the framework for assessing modern mate selection. Previous research in female mate selection has left a gap in whether and how number of children a male has can impact the perception of monetary resources he possesses and subsequently his desirability as a mate. The present investigation thus set out to examine resource-related differences among males with average ($50,001-75,000) and above average incomes (>$150,000) by analyzing data available through the online dating website, match.com. Furthermore, the geographic locations of New York, New York and Louisville, Kentucky were used to both refine results but also maintain genera lizability of findings.
    [Show full text]
  • Sexual Selection
    Sexual selection Introduction, key concepts, examples. - Pioneer ideas: Darwin, Bateman, Trivers - Male-male competition: processes and intrasexually-selected traits - Mate choice: processes and intersexually-selected traits - Polyandry, monandry, sex-role reversion... : evolutionary origin of the diversity of mating systems - Coexistence of alternative strategies ENS – Master 1 – Ecologie Evolutive Novembre 2014 David Laloi ([email protected]) Darwin’s hypothesis Natural selection (in its basic form ) does not explain appropriately the evolution of many traits, dimorphic sexual ornaments in particular: other selective pressures? 1859 The origin of species by 1871 The descent of man and means of natural selection selection in relation to sex Darwin’s hypothesis Natural selection (in its basic form ) does not explain appropriately the evolution of many traits, dimorphic sexual ornaments in particular: other selective pressures? Sexual selection Selection that results from differences in reproductive success due to competition for mate acquisition. In other words, some traits do not depend on a ‘struggle for life’ but on a ‘struggle for mating’. Darwin’s hypothesis Two main forms of sexual selection: Males compete with each other to accede to females Intrasexual selection Females are choosy in which males to mate with Intersexual selection Sexual selection: asymmetrical processes… Why males and females differ in trying to acquire mate? - All individuals can obtain more offspring when mating with more mates. - All individuals can obtain better offspring when mating with better mate. But… - gametes: large, non motile, swollen with reserves, High investment in each small number. - gametes: small, motile, with very few reserves, Low investment in each very large number. Bateman’s principle Sperm are cheaper and more numerous than eggs, thus: - a single male can easily fertilize all a female's eggs; she will not produce more offspring by mating with more than one male, - a male is capable of fathering more offspring if he mates with several females.
    [Show full text]
  • Response to Eberhard and Cordero, and Co´ Rdoba-Aguilar and Contreras-Gardun˜ O: Sexual Conflict and Female Choice
    440 Update TRENDS in Ecology and Evolution Vol.18 No.9 September 2003 important issue both theoretically and experimentally References [5], researchers ignore how female reproductive traits 1 Holland, B. and Rice, W.R. (1997) Chase-away sexual selection: intervene during fertilization. Once this is clarified, we antagonistic seduction versus resistance. Evolution 52, 1–7 2 Parker, G.A. (1979) Sexual selection and sexual conflict. In Sexual can then ascribe female traits as ‘resistant’ or Selection and Reproductive Competition in Insects (Blum, M.S. and ‘selective’. The second is to study the genetics of the Blum, N.A., eds), pp. 123–166, Academic Press female preference and associated male traits [5].A 3 Chapman, T. et al. (2003) Sexual conflict. Trends Ecol. Evol. 18, 41–47 genetic correlation is expected between both traits only 4 Cordero, C. and Eberhard, W.G. (2003) Female choice of sexually if traditional female choice is occurring. The third and antagonistic male adaptations: a critical review of some current research. J. Evol. Biol. 16, 1–6 final approach is to track the rates of origin of female 5 Simmons, L.W. (2001) Sperm Competition and its Evolutionary and male traits on phylogenies once resistance or Consequences in the Insects, Princeton University Press selectivity has been determined. This will explain the 6 Edvardsson, M. and Arnqvist, G. (2000) Copulatory courtship and prevalence of either process. cryptic female choice in the red flour beetles Tribolium castaneaum. Studies of fruit flies and water striders have Proc. R. Soc. Lond. Ser. B 267, 559–563 7 Elgar, M.A.
    [Show full text]
  • Mating Systems and Sexual Selection in Male-Pregnant Pipefishes And
    Mating Systems and Sexual Selection in Male-Pregnant Pipefishes and Seahorses: Insights from Microsatellite-Based Studies of Maternity A. G. Jones and J. C. Avise In pipefishes and seahorses (family Syngnathidae), the males provide all postzy- gotic care of offspring by brooding embryos on their ventral surfaces. In some species, this phenomenon of male ‘‘pregnancy’’ results in a reversal of the usual direction of sexual selection, such that females compete more than males for ac- cess to mates, and secondary sexual characteristics evolve in females. Thus the syngnathids can provide critical tests of theories related to the evolution of sex differences and sexual selection. Microsatellite-based studies of the genetic mating systems of several species of pipefishes and seahorses have provided insights into important aspects of the natural history and evolution of these fishes. First, males of species with completely enclosed pouches have complete confidence of paternity, as might be predicted from parental investment theory for species in which males invest so heavily in offspring. Second, a wide range of genetic mating systems have been documented in nature, including genetic monogamy in a sea- horse, polygynandry in two species of pipefish, and polyandry in a third pipefish species. The genetic mating systems appear to be causally related to the intensity of sexual selection, with secondary sex characters evolving most often in females of the more polyandrous species. Third, genetic studies of captive-breeding pipe- fish suggest that the sexual selection gradient (or Bateman gradient) may be a substantially better method for characterizing the mating system than previously available techniques. Finally, these genetic studies of syngnathid mating systems have led to some general insights into the occurrence of clustered mutations at microsatellite loci, the utility of linked loci in studies of parentage, and the use of parentage data for direct estimation of adult population size.
    [Show full text]