Diet and ecomorphological relationships of an endemic, species-poor fish assemblage in a stream in the Iguaçu National Park

Abstract

This study investigated the morphological and dietary relationships of the fish assemblage in a stream with an endemic fauna and low species richness. The ichthyofauna was sampled quarterly from September 2011 to July 2012, through the electrofishing technique. The stomach contents of 419 individuals belonging to seven species were analyzed by the volumetric method, and the ecomorphological traits of 30 specimens of each species were estimated. The main food items consumed were detritus, aquatic and terrestrial insects, and other aquatic invertebrates. We observed low levels of trophic niche breadth and diet overlap between most species. The PCA scores indicated the occurrence of three ecomorphotypes. PCA axis 1 segregated at one extreme, species with dorsoventrally depressed bodies, longer caudal peduncles, and welldeveloped swimming fins; and at the other extreme, species with compressed bodies and peduncles, and relatively larger eyes and anal fins. PCA axis 2 segregated species with elongated bodies and ventrally oblique mouths. The partial Mantel test revealed a significant correlation between diet and morphology, indicating independence from the phylogeny. The patterns observed suggest that the low richness did not result in a broadening of the species' trophic niches, or in the absence of some of the main ecomorphotypes expected.Este estudo teve como objetivos investigar as relações morfológicas e alimentares de uma assembleia de peixes com fauna endêmica e de baixa riqueza de espécies. Os peixes foram amostrados trimestralmente entre setembro de 2011 a julho de 2012, através da técnica da pesca elétrica. Foram obtidas as medidas morfométricas que possibilitaram os cálculos dos índices ecomorfológicos e analisados os conteúdos estomacais de 419 indivíduos, pertencentes a sete espécies, através do método volumétrico. Os principais itens alimentares consumidos pela assembleia de peixes foram detrito, insetos aquáticos e terrestres e outros invertebrados aquáticos. Observou-se baixos valores de amplitude de nicho trófico e de sobreposição alimentar entre a maioria das espécies. Os escores da PCA, indicaram a ocorrência de três ecomorfotipos. O eixo CP1 segregou em um extremo espécies com corpo deprimido dorso-ventralmente, pedúnculo caudal longo e as nadadeiras desenvolvidas, enquanto no outro extremo, espécies com corpos e pedúnculos comprimidos, área dos olhos e das nadadeiras anais relativamente maiores. Por outro lado, o eixo CP2 segregou espécies com corpos mais alongados, bocas ventralmente oblíquas. Através do Teste de Mantel verificou-se relação significativa entre a dieta e a morfologia. Assim, os principais padrões tróficos e ecomorfológicos verificados sugerem que a baixa riqueza, não repercutiu no alargamento do nicho trófico das espécies ou na inexistência de algum dos principais grupos ecomorfológicos.

Fish fauna in forested and rural streams from an ecoregion of high endemism, lower Iguaçu River basin, Brazil

“…While others similar large tributaries from upper Paraná River system (e.g., Paranapanema, Tietê, Grande) include more than 150 fish species (Langeani et al 2007, Duke Energy 2008, the inventories along Iguaçu River basin have not exceeded much more than one hundred species, added those introduced (Baumgartner et al 2012). Its low species richness is more evident in smaller spatial scales, where local fish assemblages of streams have presented between six to 12 species (Vitule & Abilhoa 2003, Bifi et al 2006, Abilhoa et al 2008, Neves et al 2015, Larentis et al 2016, while others streams with similar magnitude from Paraná system, between 13 to 41 species (Castro et al 2003, Delariva & Silva 2013, Cetra et al 2012, Vidotto-Magnoni et al 2015.…”

“…To the south of the hydrographical divisor of these there basins are streams that flows to lower Iguaçu River, whose ichthyofauna have been only recently studied (Neves et al 2015, Larentis et al 2016. Due to the historical process of land use and occupation, these streams present different percentages of vegetal cover among their watersheds.…”

“…Due to the historical process of land use and occupation, these streams present different percentages of vegetal cover among their watersheds. The use gradient extends from rural streams, with intense agricultural activity (IBGE 2015, Yamamoto et al 2016, to preserved streams located partially or integrally within conservation units, like those into the Iguaçu National Park (INP) (Neves et al 2015).…”

Ecomorphological relationships of fish assemblages in a trans-Andean drainage, Upper Magdalena River Basin, Colombia

“…Therefore, understanding ecomorphological patterns in fish assemblages can play an important role in conservation, because species losses not only represent the disappearance of biological entities, but also the alteration of ecological groups and the loss of functional roles that species play in the ecosystem (Neves et al, 2015). Habitat loss by damming, mining, 10 e170037 [10] deforestation, and pollution is one of the main threats to the Neotropical fish fauna (Barletta et al, 2010;Anderson, Maldonado-Ocampo, 2011;Pelicice et al, 2017).…”

“…However, most of the ecomorphological studies in Neotropical fish communities have focused on cis-Andean ecosystems (Casatti, Castro, 2006;Ferreira, 2007;Oliveira et al, 2010;Soares et al, 2013;Neves et al, 2015;Pessanha et al, 2015;RoaFuentes et al, 2015;Novakowski et al, 2016;Prado et al, 2016), which have shown significant relationships between morphological attributes that respond to ecological affinities such as trophic ecology or habitat use. According to Neves et al (2015), if the theoretical framework of ecomorphological studies is expanded to different geographical areas with high levels of endemism and relatively low richness, it would help to elucidate the different patterns of assemblage structure and interspecific interactions within habitats. Therefore, this study extends the theoretical framework of the ecomorphological hypothesis to the trans-Andean region in Colombia.…”