Fitness consequences of individual specialisation in resource use and trophic morphology in European eels |
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Authors: | Julien Cucherousset Anthony Acou Simon Blanchet J Robert Britton William R C Beaumont Rodolphe E Gozlan |
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Institution: | 1.Centre for Conservation Ecology and Environmental Sciences, School of Applied Sciences,Bournemouth University,Poole,UK;2.CNRS, UPS, ENFA, UMR5174,Laboratoire EDB (évolution et Diversité Biologique),Toulouse,France;3.UPS, UMR5174, Laboratoire évolution et Diversité Biologique (EDB),Université de Toulouse,Toulouse,France;4.Muséum National d’Histoire Naturelle, UMR 7208 BOREA, Centre de Recherche et d’Enseignement des Systèmes C?tiers,Station Marine de Dinard,Dinard,France;5.U.S.R. 2936,Station d’Ecologie Expérimentale du CNRS à Moulis 09200,Moulis,France;6.Game and Wildlife Conservation Trust,Salmon and Trout Research Centre,Wareham,UK |
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Abstract: | Individual specialisation can lead to the exploitation of different trophic and habitat resources and the production of morphological
variability within a population. Although the ecological causes of this phenomenon are relatively well known, its consequences
on individual fitness are less recognised. We have investigated the extent of individual specialisation in resource use and
trophic morphology and its fitness consequences through a combination of tagging–recapture, stable isotope analyses and telemetry.
The European eel (Anguilla anguilla) was the model species as it displays significant variability in head shape. Independent to their body length, individuals
with broader heads displayed a significantly higher trophic position (δ15N) than individuals with narrower heads. This corresponded with a significantly higher proportion of prey fish in their diet
compared with invertebrates and was associated with the use of a habitat niche located further from the river bank. The European
eel therefore provides a rare empirical example of individual specialisation in resource use and trophic morphology in a natural
population occurring at a very small spatial scale. Individuals with intermediate head morphology displayed lower body condition
(a proxy of fitness) than individuals with extreme head morphology (i.e. narrower and broader headed individuals), demonstrating
the existence of disruptive selection associated with individual specialisation. |
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