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This file is part of the following reference:
Gainsford, Ashton (2016) A multi-disciplinary evaluation
of the hybrid anemonefish Amphiprion leucokranos:
behaviour shaping evolutionary outcomes of hybridization.
PhD thesis, James Cook University.
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http://dx.doi.org/10.4225/28/58c62be6f0a34 mailto:[email protected]
A MULTI-DISCIPLINARY EVALUATION OF THE
HYBRID ANEMONEFISH AMPHIPRION LEUCOKRANOS:
BEHAVIOUR SHAPING EVOLUTIONARY OUTCOMES
Thesis submitted by
Ashton Gainsford (BSc Hons)
In November 2016
For the degree of Doctor of Philosophy
College of Science and Engineering
James Cook University
Townsville, Queensland, Australia
STATEMENT OF CONTRIBUTION OF OTHERS
A number of collaborators and colleagues have contributed in various ways to this thesis and the subsequent manuscripts which are published, submitted or in preparation for submission. A summary of these contributions are listed below.
Nature of Assistance Contribution Co-contributors
Intellectual support Project design Dr. L. van Herwerden (JCU) & Prof. G.P. Jones (JCU, ARC CoE)
Proposal writing Dr. L. van Herwerden (JCU) & Prof. G.P. Jones (JCU, ARC CoE)
Data analysis support Chapter 2: S.R. Montanari ([email protected]) & Dr. M. van der Meer (JCU)
Statistical support Chapter 5: Prof Emer. R. Jones (JCU)
Editorial assistance Chapters 2-4: Dr. L. van Herwerden (JCU), Prof. G.P. Jones (JCU, ARC CoE); Chapter 4: Dr. J-P. Hobbs (CU); Chapter 4-5: H. Epstein ([email protected], ARC CoE)
Data collection Fieldwork assistance Dr. M. Lal (JCU), K. Thomas Brown (USP), T. Millitz (JCU), Dr. J-P. Hobbs (CU), H. Campbell, Dr. L. Bostrom-Einarsson (JCU, ARC CoE), Dr. H.B. Harrison (JCU, ARC CoE), T. Bowling, & Dr. M.C. Bonin (ARC CoE)
Laboratory assistance F.M. Heindler (JCU) & H. Epstein ([email protected], ARC CoE)
Diving & boating support
L. Choquette & Solomon Dive Adventures, Mahonia Na Dari, Kimbe Bay & (NIMRF, Kavieng)
Histology S. Reilly (JCU)
Otolith sectioning Dr. D. Lou (Tropical Fish Ageing)
Financial assistance Research funding Prof. G.P. Jones (JCU, ARC CoE), Dr. J-P. Hobbs (CU), & Dr. L. van Herwerden (JCU)
The research presented and reported in this thesis was conducted in compliance with the National Health and Medical Research Council (NHMRC) Australian Code of Practice for the Care and Use of Animals for Scientific Purposes, 7th Edition, 2004 and the Qld Animal Care and Protection Act, 2001. The proposed research study received animal ethics approval from the JCU Animal Ethics Committee Approval Number A1633 and A1791.
“Solitude is a human presumption. Every quiet step is thunder to beetle life underfoot, a tug of impalpable thread on the web pulling mate to mate and predator to prey, a beginning or an end. Every choice is a world made new for the chosen.” – Barbara Kingsolver
The journey to completing my dissertation was not travelled alone and I will be forever
grateful to my family, friends and colleagues who have shared in this experience. Each small
kindness contributed to me finishing, which sometimes felt beyond reach. Many favours, words of
encouragement, insights, late night phone calls, blind faith and understanding were shared without
question. You’re all lovely and wonderful and I will never forget it.
A few special mentions – Carol and Brian Gainsford, your generosity inspires me and I am
proud beyond measure to be your daughter. Thank you for always encouraging curiosity and
adventure, even though it has put considerable distance between us. You have given me spirit and
strength, and a family with unconditional love. Thank you for your unwavering support every step
of the way.
Yvette, Dean and Chiara-Lee – you are the craziest, kindest and most spirited bunch of
bloody drongos anyone could ever hope to call family. Thank you for reminding me to see humour
in each and every moment and for sharing in my trials and triumphs. You are my best friends.
Mary – you taught me how to catch a fish and a hell of a lot about research in the field for
which I will be forever grateful; thanks for all the epic adventures and laughs along the way. Hannah
– your enthusiasm for my research, challenging conversations, tireless assistance in the lab and
editing in the final weeks of this long journey are appreciated beyond words. Lisa, Gigi, Emma and
Margaux – you are one solid group of fearless, strong ladies. Your friendship has picked me up and
empowered me to keep moving forward. Thank you for always celebrating each other’s successes,
big and small – your joy is powerful and contagious.
To my supervisors, Lynne and Geoff, I cannot thank you enough for the time and effort
you have invested in developing me as a researcher, whilst also juggling your own demanding lives
and many responsibilities. Lynne, you took me under your wing with blind faith, you have
challenged my thinking and ability, and offered me many opportunities to increase my skills and
responsibilities in academia. Thank you for your time, guidance and friendship.
Formally, I would also like to acknowledge and thank the following institutions and
funding bodies for financial support of my research and professional development: Sea World
Research and Rescue Foundation Inc., the College of Marine and Environmental Sciences and
Australian Research Council Centre of Excellence for Coral Reef Studies, and the Comparative
Genomics Centre at James Cook University, and the Australian Coral Reef Society. Finally, I was
generously supported by an Australian Postgraduate Award for three and a half years with full
tuition waiver while completing my dissertation, as well as a living stipend through the Graduate
Research Scheme (JCU) to complete my dissertation writing, for which I am beyond grateful.
Hybridization is an evolutionarily significant and common occurrence in nature.
Interspecific breeding between closely related taxa challenges established phylogenies and
questions what constitutes a species; where hybridization may drive rapid evolution of taxa and
provide a source of evolutionary novelty to ecosystems. Despite the enhanced study of
hybridization in recent time, a clear understanding of the mechanisms which initiate and maintain
hybridization remains limited. Hybrid zones are ideal for testing theoretical questions regarding
speciation and elucidating patterns of variation among species. For many taxa, reproductive success
is skewed towards large, socially dominant individuals within groups, and reproductive traits and
mating systems are expected to influence the outcomes of hybridization and gene exchange between
hybridizing species. In this thesis, I addressed how ecology and behaviour contribute to
maintenance and persistence of the Amphiprion leucokranos hybrid zone. This research employed
a combination of ecological, phylogenetic and population genetic assays, as well as an observational
study and behavioural experiment to test key concepts of the importance of hybridization to
evolution of species.
A suite of 42 novel and published microsatellite markers were developed and tested in
Chapter 2 to facilitate investigation into the relatedness of taxa within the hybrid zone. The
influence of ecology and behaviour on the outcomes of hybridization were tested in Chapter 3,
addressing how habitat use and relative size differences of parent species and hybrids drive patterns
of gene exchange. Findings confirmed A. leucokranos to be the hybrid of closely related
A. chrysopterus and A. sandaracinos, and subsequently verified that behavioural isolation, habitat
use and species-specific size differences dictates the direction and degree of back-crossing and
subsequent introgression. Hybridization took place exclusively with A. chrysopterus in the
dominant female rank and the smaller A. sandaracinos in the sub-dominant male rank, based on
mtDNA cytochrome b and multiple nDNA microsatellite loci. Overlap in habitat, depth and host
anemone use was found, with hybrids intermediate to parents and co-habitation in over 25% of
anemones sampled. Hybrids, intermediate in body size, colour and pattern, were classified 55% of
the time as morphologically first generation hybrids relative to parents, whereas 45% of hybrids
were more like A. sandaracinos, suggesting back-crossing. Unidirectional introgression of
A. chrysopterus mtDNA into A. sandaracinos via hybrid back-crosses was found, wi