Is coexistence between non-native and native Erythrinidae species mediated by niche differentiation or environmental filtering? A case study in the upper Paraná River floodplain

Abstract

The limiting similarity theory predicts that divergence in the functional traits of native and introduced species is an essential component in species establishment, as introduced species must occupy a niche that is unoccupied by resident species. On the other hand, the environmental filtering hypothesis predicts convergence between introduced and native species, as both possess traits that make them adapted to the local abiotic environment. Morphology, spatial co-occurrence, diet, feeding selectivity, and niche breadth and overlap of Erythrinidae were evaluated to detect possible mechanisms acting in the coexistence between non-native and native species. Native (Hoplias sp. B and Hoplias cf. malabaricus) and nonnative (Hoplerythrinus unitaeniatus and Hoplias mbigua) species presented differences in morphological traits, spatial cooccurrence, diet, selectivity, and niche breadth and overlap. The mechanisms mediating species coexistence seem to vary according to species. The absence of spatial and feeding overlap suggests that non-native species H. unitaeniatus occupy a different niche than native species, supporting its successful establishment without eliminating the native species. However, low feeding overlap and similar morphologies between non-native and native species of Hoplias point to environmental filters; in this case, the non-native H. mbigua is able to establish due to similarities in functional traits.Keywords: Competition, Co-occurrence, Fish feeding, Morphology, Predation.Teorias sobre nicho ecológico afirmam que divergência em traços funcionais entre espécies nativas e introduzidas são essenciais ao estabelecimento da espécie introduzida, pois estas devem ocupar um nicho não utilizado pelas espécies residentes. Por outro lado, a teoria de filtros ambientais afirma a convergência entre espécies introduzidas e nativas, pois ambas possuem traços funcionais que fazem com que essas espécies estejam mais adaptadas as variáveis ambientais. Foram avaliadas a morfologia, ocorrência espacial, dieta, seletividade alimentar, sobreposição e largura de nicho em Erythrinidae para detectar possíveis mecanismos atuando na coexistência de espécies nativas e não nativas. Espécies nativas (Hoplias sp. B e Hoplias cf. malabaricus) e não nativas (Hoplerythrinus unitaeniatus e Hoplias mbigua) apresentaram diferenças em todos os atributos testados. Os mecanismos mediando a coexistência de espécies nativas e não nativas parecem variar de acordo com a espécie considerada. A ausência de sobreposição espacial e na dieta sugere que a espécie não nativa H. unitaeniatus ocupa um nicho distinto que as espécies nativas, favorecendo seu estabelecimento sem eliminar as espécies nativas, apontando para segregação de nicho. Por outro lado, morfologias similares, porém com diferentes dietas foram observadas para as espécies de Hoplias, sugerindo que as espécies coexistem devido à filtros ambientais, assim, neste caso, a espécie não nativa H. mbigua é capaz de se estabelecer no novo ambiente devido à similaridades em traços funcionai...

Stable isotopes reveal niche segregation between native and non‐native Hoplias in a Neotropical floodplain

“…Our results also showed that the native Hoplias has a wider niche area, whereas the non-native obtains resources at higher trophic levels. A similar outcome was observed by Alves, Figueiredo, et al (2017) For Hoplias, we expected trophic segregation to be an outcome of distinct foraging behaviours derived from differential ecomorphological features, as hypothesised by Strictar-Pereira et al (2017) for the same floodplain. The native Hoplias sp.…”

“…B presented higher width and height of the head with eyes dorsoventrally positioned, indicating that it occupies benthic positions and is able to ingest larger prey than its non-native congeneric H. mbigua (Strictar-Pereira et al, 2017). Diet composition analysis showed that the native Hoplias consumes preys in lower trophic levels (bottom feeders), whereas the non-native Hoplias diet is mostly derived (over 55%) from piscivorous fish (Strictar-Pereira et al, 2017). Indeed, the isotopic trophic position from this study showed that the non-native species is feeding at a higher trophic level (TP = 3.1) compared to the native species and presents a low proba- McHugh, Budy, Thiede, & VanDyke, 2008;Pilger, Gido, & Propst, 2010;Vander-Zanden, Casselman, & Rasmussen, 1999) and may even decrease the length of food chains (Maceda-Veiga, Nally, & Sostoa, 2018).…”

“…The native Hoplias sp. B presented higher width and height of the head with eyes dorsoventrally positioned, indicating that it occupies benthic positions and is able to ingest larger prey than its non-native congeneric H. mbigua (Strictar-Pereira et al, 2017). Diet composition analysis showed that the native Hoplias consumes preys in lower trophic levels (bottom feeders), whereas the non-native Hoplias diet is mostly derived (over 55%) from piscivorous fish (Strictar-Pereira et al, 2017).…”

“…As such, new insights are needed to understand how these species interact and coexist since the H. mbigua introduction. Evidence of trophic niche overlap between the two Hoplias species has been reported through stomach content analysis (Strictar-Pereira et al, 2017) and with stable isotopes analysis (Phillipsen, Hauser, & Benedito, 2015) in the Paraná River floodplain. Additionally, an ecomorphological analysis suggested that the native Hoplias can ingest larger prey and occupy more benthic positions in the water column than the non-native Hoplias (Phillipsen et al, 2015) which could be the underlying explanation for coexistence.…”

“…Coexistence between native and non-native species might be mediated through different mechanisms (Jesche & Heger, 2018); however, niche differentiation (De Léon, Podos, Gardezi, Herrel, & Hendry, 2014) and environmental filtering (Mouillot, Dumay, & Tomasini, 2007;Southwood, 1977) have been suggested to be the dominant underlying processes for phylogenetically close species (Strictar-Pereira, Mise, Tencatt, Baumgartner, & Agostinho, 2017). According to limiting similarity theory, native and non-native species can only coexist if they have distinct functional traits, such as foraging behaviour or diet selectivity, enabling them to share common abundant resources or specialise on distinct limited resources (De Léon et al, 2014).…”