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Morphological and ecological divergence in the hybridogenic fish complex Squalius alburnoides

Smith, Victoria Alexandra Joana


Victoria Alexandra Joana Smith


I. G. (Ian G.) Cowx

Stuart Humphries

Leandro Monteiro

Andrew David Nunn


Polyploidy in animals is rare and often associated with asexual reproduction in all-female lineages. Although some authors believe these lineages to be evolutionary dead ends there is increasing evidence that some species can adapt efficiently and ultimately evolve into a new sexually reproducing species. The hybrid fish complex Squalius alburnoides, endemic to the Iberian Peninsula, is one such complex, that is composed of several groups with varying genomic compositions of the maternal and paternal ancestral genome. This, coupled with novel reproductive tactics has lead to the presence of diploid, triploid and tetraploid individuals in a number of populations around the peninsula.

One of the objectives aimed to identify if morphological differences could be found with the species and whether it would be possible to identify the ploidy of an individual using morphological features alone. Differences between two ploidy groups, diploid males and triploids, were demonstrated using morphology of scales, head and body from fish collected from the Guadiana river basin in Portugal, using geometric morphometric methods. The morphological differences found using scale shape allowed the creation of a prediction function, capable of identifying the ploidy group of individuals of unknown ploidy using scale morphology alone, with a confidence rate of 75% and 92% respectively for diploid males and triploids. Diploid females were accurately classified 6.3% of the time, due to morphological similarities with triploids, with which they were often mistaken for. Ecological analyses on dietary and habitat selection were coupled with age and growth data to further discover if differences between ploidy levels existed. Results showed that there were differences found, and that dietary composition could be linked to habitat selection and morphological adaptation.

This thesis has expanded the available knowledge of the species, specifically with relation to morphological differences. It has also provided a framework for future identification of S. alburnoides individuals without the need for invasive and expensive methodologies.


Smith, V. A. J. (2012). Morphological and ecological divergence in the hybridogenic fish complex Squalius alburnoides. (Thesis). University of Hull. Retrieved from

Thesis Type Thesis
Deposit Date Dec 7, 2012
Publicly Available Date Feb 22, 2023
Keywords Biological sciences
Public URL
Additional Information Department of Biological Sciences, The University of Hull
Award Date Apr 1, 2012


Thesis (46.5 Mb)

Copyright Statement
© 2012 Smith, Victoria Alexandra Joana. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright holder.

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