Morphological Variation and Diversification in Australian Neriid Flies Elizabeth Cassidy Supervised by: Russell Bonduriansky THESIS SUBMITTED FOR THE DEGREE OF MASTER OF PHILOSOPHY Evolution and Ecology Research Centre School of Biological, Earth and EnvironMental Sciences University of New South Wales October 2012 PLEASE TYPE THE UNIVERSITY OF NEW SOUTH WALES Thesis/Dissertation Sheet Surname or Family name: Cassidy First name: Elizabeth Other name/s: Jane Gerard Abbreviation for degree as given in the University calendar: MPhil School: School of Biological, Earth & Environmental Faculty: Science Sciences; Evolution & Ecology Research Centre Title: Morphological Variation and Diversification in Australian Neriid Flies Abstract 350 words maximum: (PLEASE TYPE) Morphological variation is a result of complex interactions between physiological constraints, selection pressures and ecological conditions. All of these factors are vital in the understanding of the evolution of morphological adaptations. In this thesis, I examine three aspects of the phenotypic plasticity and morphological variation in two species of neriid flies, Telostylinus angusticollis and Telostylinus lineolatus. Chapter one examines allometric constraints on the diversification of populations. Static allometry slope is generally thought to constrain adaptation and diversification. We examined the diversification of static allometry by manipulating larval nutrient concentration and comparing allometric slopes in sexual and non-sexual traits across populations. We found evidence of slope diversification within T. angusticollis and T. lineolatus in a sexual trait. Our results suggest the diversification of static allometry slope can be driven by sexual selection. Following this, chapter two discusses sexual selection and its impact on diversification in males and females. Using reaction norms for nutrient concentration in a range of sexual and non-sexual body shape components, we identify different patterns of morphological diversification between the sexes. In addition to this, the patterns of diversification seen in males suggest that sexual selection is acting upon male body shape as a whole, rather than specific morphological traits. We consider the ecological and selective forces contributing to the diversification of the sexes. Chapter three examines another aspect of larval ecology, group relatedness, and its benefits or disadvantages. We find that fly larvae gain an advantage from being housed with closely related individuals, and emerge larger as adults, congruent with the kin selection hypothesis. These three chapters outline some of the different factors contributing to morphological variation and highlight the importance and complexity of phenotypic plasticity. Declaration relating to disposition of project thesis/dissertation I hereby grant to the University of New South Wales or its agents the right to archive and to make available my thesis or dissertation in whole or in part in the University libraries in all forms of media, now or here after known, subject to the provisions of the Copyright Act 1968. I retain all property rights, such as patent rights. I also retain the right to use in future works (such as articles or books) all or part of this thesis or dissertation. I also authorise University Microfilms to use the 350 word abstract of my thesis in Dissertation Abstracts International (this is applicable to doctoral theses only). …………………………………………………………… ……………………………………..……………… ……….……………………...…….… Signature Witness Date The University recognises that there may be exceptional circumstances requiring restrictions on copying or conditions on use. Requests for restriction for a period of up to 2 years must be made in writing. Requests for a longer period of restriction may be considered in exceptional circumstances and require the approval of the Dean of Graduate Research. FOR OFFICE USE ONLY Date of completion of requirements for Award: i ORIGINALITY STATEMENT ‘I hereby declare that this submission is my own work and to the best of my knowledge it contains no materials previously published or written by another person, or substantial proportions of material which have been accepted for the award of any other degree or diploma at UNSW or any other educational institution, except where due acknowledgement is made in the thesis. Any contribution made to the research by others, with whom I have worked at UNSW or elsewhere, is explicitly acknowledged in the thesis. I also declare that the intellectual content of this thesis is the product of my own work, except to the extent that assistance from others in the proJect's design and conception or in style, presentation and linguistic expression is acknowledged.’ Signed Date ii iii ABSTRACT Morphological variation is a result of complex interactions between physiological constraints, selection pressures and ecological conditions. All of these factors are vital in the understanding of the evolution of morphological adaptations. In this thesis, I examine three aspects of the phenotypic plasticity and morphological variation in two species of neriid flies, Telostylinus angusticollis and Telostylinus lineolatus. Chapter one examines allometric constraints on the diversification of populations. Static allometry slope is generally thought to constrain adaptation and diversification. We examined the diversification of static allometry by manipulating larval nutrient concentration and comparing allometric slopes in sexual and non-sexual traits across populations. We found evidence of slope diversification within T. angusticollis and T. lineolatus in a sexual trait. Our results suggest the diversification of static allometry slope can be driven by sexual selection. Following this, chapter two discusses sexual selection and its impact on diversification in males and females. Using reaction norms for nutrient concentration in a range of sexual and non-sexual body shape components, we identify different patterns of morphological diversification between the sexes. In addition to this, the patterns of diversification seen in males suggest that sexual selection is acting upon male body shape as a whole, rather than specific morphological traits. We consider the ecological and selective forces contributing to the diversification of the sexes. Chapter three examines another aspect of larval ecology, group relatedness, and its benefits or disadvantages. We find that fly larvae gain an advantage from being housed with closely related individuals, and emerge larger as adults, congruent with the kin selection hypothesis. These three chapters outline some of the different factors contributing to morphological variation and highlight the importance and complexity of phenotypic plasticity. iv Contents Introduction .............................................................................................................. 1 Diversification of static allometries in Australian neriid flies ...................................... 5 ABSTRACT .......................................................................................................................... 6 INTRODUCTION .................................................................................................................. 7 METHODS ........................................................................................................................ 10 RESULTS ........................................................................................................................... 13 DISCUSSION ..................................................................................................................... 18 REFERENCES ..................................................................................................................... 23 Sex-specific patterns of diversification in reaction norms for morphological traits ... 26 ABSTRACT ........................................................................................................................ 27 INTRODUCTION ................................................................................................................ 28 METHODS ........................................................................................................................ 33 RESULTS ........................................................................................................................... 36 DISCUSSION ..................................................................................................................... 38 REFERENCES ..................................................................................................................... 45 Larvae of the neriid fly Telostylinus angusticollis benefit by interacting with kin ...... 51 ABSTRACT ........................................................................................................................ 52 INTRODUCTION ................................................................................................................ 53 METHODS ........................................................................................................................ 56 RESULTS ........................................................................................................................... 59 DISCUSSION ..................................................................................................................... 62 REFERENCES ....................................................................................................................