Abstract
Abstract: We aimed to evaluate the relationship between form and function of two Loricariidae species (Hypostomus punctatus and Parotocinclus maculicauda) from a Neotropical coastal stream. We performed morphological-dietary analysis and discussed their coexistence strategies, as well. We hypothesized that both species use similar food resources according to their morphology but differences in habitat use facilitate their coexistence. In order to test this hypothesis, morphology, diet and habitat use were analyzed for both species. Trophic variance and the Pianka Niche Overlap index were calculated to explore the differences in trophic niche. Correlations between species abundance and water flow were applied to test habitat use. Principal Component Analysis and one Permutational Multivariate Analysis of Variance were applied to test differences between morphology and diet of both species. Morphological-dietary relationships were tested with Mantel test correlations. Total abundance of H. punctatus was higher in the stream channel with higher water flow. The dominant food items were sediment and organic matter for both species, and high trophic niche overlap was revealed. Additionally, morphology did not explain feeding habits for both species. Morphological characteristics were significantly different, especially for intestine length, relative area of the dorsal fin, ventral flattening and mouth attributes. The study site was rich in sand sediment, mud, and clay that are not considered good substrates to the establishment and growing of periphyton, which is an important trophic resource to Loricariidae species. Here, low consumption of periphyton can provide a possible explanation for the feeding similarity and the weak morphological-dietary relationships for both species. Thus, the environmental conditions can be more important for diet composition when compared to the similar and specialized morphology of loricariids.
Highlights
Fish coexistence, in special the one involving close related species, is an important point in the understanding of natural community organization (Wooton 1990)
We present here a comparative analysis of morphology, diet and habitat use of two of these Loricariidae species, namely Parotocinclus maculicauda (Steindachner, 1877) and Hypostomus punctatus Valenciennes, 1840
Sand and mud were the most abundant substrate types registered in both habitats totalling 97.4% in stream channel and 84.5% in stream bank
Summary
In special the one involving close related species, is an important point in the understanding of natural community organization (Wooton 1990). Feeding strategies reflect morphology and individual foraging performance (Douglas & Matthews 1992, do Carmo et al 2015) and are frequently described by those corporal characters related to fish movement (Celestino et al 2017, Conde-Saldaña et al 2017) as well as feeding tactics (Ramírez et al 2015) The synergy of those aspects, of fish form and function, can be well described by the ecomorphological approach (Oliveira et al 2010, Feilich & López-Fernández 2019) and explain habitat occupation (Sabino & Castro 1990, Wood & Bain 1995, Tulli 2012) and coexistence of some close related species (Villares-Junior et al 2016). It is expected that when close related species coexist, niche breadth is narrowed and feeding specialization reduce competition chance (MacArthur 1972, Young et al 2010)
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