Long term patterns in the late summer trophic niche of the invasive pumpkinseed sunfishLepomis gibbosus

Abstract

-Quantifying the trophic dynamics of invasive species in novel habitats is important for predicting the success of potential invaders and evaluating their ecological effects. The North American pumpkinseed sunfish Lepomis gibbosus is a successful invader in Europe, where it has caused negative ecological effects primarily through trophic interactions. Here, we quantified variations in the late summer trophic niche of pumpkinseed during establishment and integration in the mainstem of the Guadiana river, using stomach content analyses over a period of 40 years. Pumpkinseed showed a shift from trophic specialization during establishment to trophic generalism during integration. These results were concomitant with an increase in diet breadth that was accompanied by higher individual diet specialization particularly in large individuals. Irrespective of their drivers, these changes in trophic niche suggest that the potential ecological effects of pumpkinseed on recipient ecosystems can vary temporally along the invasion process.Key-words: invasive species / trophic niche / diet shift / diet breadth / individual diet specialization Résumé -Tendances à long terme de la niche trophique estivale de la perche soleil Lepomis gibbosus invasive. La quantification de la dynamique trophique des espèces envahissantes dans leur aire d'introduction est importante pour prédire leur succès d'invasion et évaluer leurs potentiels effets écologiques. La perche soleil − Lepomis gibbosus − est une espèce originaire d'Amérique du Nord qui a été largement introduite en Europe où elle induit des effets écologiques négatifs principalement par des interactions trophiques. Dans cette étude, nous avons quantifié les variations de niche trophique de la perche soleil en fin d'été pendant les phases d'établissement et d'intégration dans le cours principal de la rivière Guadiana (Portugal) en comparant des contenus stomacaux sur une période de 40 ans. Nos résultats ont permis de démontrer que la perche soleil a modifié son régime alimentaire durant cette période en passant d'un régime spécialiste pendant la phase d'établissement à un régime généraliste pendant la phase d'intégration. En parallèle, nous avons également observé une augmentation de la taille de la niche trophique de la population qui était accompagnée d'une augmentation de la spécialisation trophique individuelle, notamment chez les individus les plus grands. Indépendamment des causes induisant ces changements de niche trophique, nos résultats suggèrent donc que les effets écologiques potentiels de la perche soleil sur les écosystèmes aquatiques peuvent varier pendant le processus d'invasion biologique.Mots-clés : espèce envahissante / niche trophique / régime alimentaire / spécialisation trophique individuelle

Dietary niche divergence between two invasive fish in Mediterranean streams

“…Indeed, plant material was of negligible importance in the diet of pumpkinseed but was commonly found and in high proportions in the diet of cichlid. This is consistent with previous studies indicating that plant material is key in the diet of cichlids in native (Gutierrez et al, 1986;Yafe et al, 2002) and invaded areas (Ribeiro et al, 2007), but that pumpkinseed seldom uses this resource in both native (Mittelbach, 1984;Mittelbach et al, 1992) and invaded areas (Godinho et al, 1997;García-Berthou and Moreno-Amich, 2000;Gkenas et al, 2016). This may at least to some extent reflects variations in morphological traits and feeding capabilities between species, as for instance the presence of pharyngeal jaw apparatus in pumpkinseeds may potentiate the use of hardshelled prey relative to other resources (Wainwright, 1996).…”

“…Both species are generally less than 13 cm in total length (TL), live up to 7 years and mature in 2 years, and build and guard spawning nests and fry (Rios-Cardenas and Webster, 2005;Ribeiro et al, 2008;Ribeiro and Collares-Pereira, 2010). The pumpkinseed is invertivore whereas the cichlid is omnivore, though both prey upon macroinvertebrates, shifting from small, soft-bodied towards large, hard-shelled prey during ontogeny (Godinho et al, 1997;Ribeiro et al, 2007, Gkenas et al, 2016.…”

“…García-Berthou and Moreno-Amich, 2000;Almeida et al, 2014). The evidence available from singlespecies studies indicates that pumpkinseed and the cichlid display some variations in dietary niche, differing in the use of plant material but preying on similar macroinvertebrates (Godinho et al, 1997;Ribeiro et al, 2007;Gkenas et al, 2016). However, food resource use and dietary niche of the two species when in sympatry have never been quantified, particularly during the dry season, when macroinvertebrates tend to be in short supply (Pires et al, 2000).…”

Microhabitat interactions of non-native pumpkinseedLepomis gibbosusin a Mediterranean-type stream suggest no evidence for impact on endemic fishes

“…The first detailed study on the habitat use of L. gibbosus and its interactions with native fish species was undertaken in a small river catchment of southern England (Klaar et al, 2004), where escapee L. gibbosus from floodplain ponds and reservoirs have become established. This and follow-up studies (Vilizzi et al, 2012;Stakėnas et al, 2013) revealed strong habitat associations between L. gibbosus and native brown trout Salmo trutta, but suggested little or no impact (Gkenas et al, 2016). Although these reports are usually from lentic systems (Cucherousset et al, 2009), a recent study from a stream system in Spain revealed adverse aggressive impacts by L. gibbosus on non-native crayfish and especially endemic fishes and frogs (Almeida et al, 2014).…”

“…The latter studies have usually provided contrasting conclusions suggesting either potential ecological consequences or relatively harmless impacts (Godinho et al, 1997;Gutiérrez-Estrada et al, 2000;Villeneuve et al, 2005;Cucherousset et al, 2009;Almeida et al, 2014). However, despite the species' long-time presence in Europe and its fast spread across Anatolia, there have been only few studies on its habitat interactions in this area and virtually none in southern Europe (Gkenas et al, 2016).…”