A perda de habitat decorrente de usos do solo promove alterações na estruturação morfológica da fauna de peixes em riachos neotropicais?

Abstract

Studies about the ecomorphological structure of fish fauna is important to understand the relationship between the occurrence of morphotypes and the environmental conditions in streams. In this study we hypothesize that fish communities present lower morphological diversity in environmental conditions where habitat loss is more severe. For this, the ecomorphological structure of ichthyofauna and environmental variables were evaluated in three groups of streams (preserved, rural and urban) in the basin of the lower Iguaçu River. We intend to answer the following questions: i) there is habitat simplification and homogenization in more anthropized streams? ii) are the fish morphotypes correlated with the habitat configuration found in streams? iii) which are the indicators of environmental degradation best explain the differences in the ecomorphological structure between the groups of streams?. The environmental variables measured and the fish collection were carried out concomitantly in four collections at different climatic seasons between May 2015 and February 2016, and from March 2017 to September 2018. The fish were sampled through the electrofishing technique, identified and performed 26 morphometric measures and six relative areas of individuals belonging to 29 species. The classification of the morphotypes was made from 21 ecomorphological indexes evaluated through Principal Component Analysis (PCA). There was similarity in the composition of the fish fauna related to the morphotypes (nectonic, nectobenthic, benthic, margin and surface), in the three groups of streams, although the species that composed them had a remarkable reduction in their abundance, besides the absence of rare species in more degraded environments. The morphotype that contributed to dissimilarity through the Similarity Percentage Analysis (SIMPER) between the preserved and rural streams was nectonic. Urban streams differed from the others mainly by the surface morphotype. The ordering analysis RLQ surface morphotype was associated to urban streams characterized by higher percentages of urbanized areas, greater width with meso - habitat of potions, sandy substrate, higher conductivity and turbidity. Margin morphotype was correlated to rural streams, characterized by substrate of gravel and pebbles.

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The nectonic, benthic and nectobenthic morphotypes were associated to the preserved streams, with forested environments, structured and diversified micro-habitat with trunks and branches, rocky substratum, and higher values of dissolved oxygen. It was verified that the combination of the environmental variables that result from alterations resulting from the loss of vegetation and silting resulted in habitat homogenization and reduction of morphotypes, as well as predominance of morphotypes composed of tolerant and generalist species.