Efeitos da distância e do ambiente nos parâmetros vocais de quatro espécies de aves da floresta amazônica de terra firme

Abstract

The search for information that allows us to understand the causes, consequences and patterns of phenotypic variation has been among the most important topics of Ecology. Simply put, we know that the similarity between two observations decreases as the distance among them increases. It’s known that, despite the distance, organisms living in similar environments share common traces, as well as organisms living closer but in different environments can diverge phenotypically. Generally, the understanding of these processes leads us to comprehend how organisms survive, reproduce, adapt and evolve. Bird vocalizations are phenotypic traces that allow us to look how certain processes generate variation. The Passeriformes order is divided into Oscine and Suboscine suborders, which differ manly in the way by how vocalizations can exhibit spatial variation. Oscine birds have special neural structures adapted to learn how to sing, while in Suboscine birds’ vocalizations are not learned, but transmitted hereditarily. In the present study, we investigate the effects of geographical distance and environment on the vocal parameters of four passerine species from Amazonian upland forests, being two Oscine and two Suboscine species. To achieve it, we used autonomous recording units spread in a area of 500km2 in which we surveyed 107 spots on primary forest and 44 on secondary forest. To analyze the relationship between geographical distance and vocal parameters we performed Mantel’s tests, and to evaluate the effect of the kind of environment we performed Wilcoxon’s tests. Only two vocal parameters from a suboscine species showed strong relationship with geographical distance, in a random pattern of variation across space. None of the vocal parameters seemed to be strongly affected by the environment. Overall, temporal parameters seemed to vary more with distance than spectral parameters. The detected variation in a suboscine species and the absent of variation on oscine species contribute to debate around learned and non-learned songs; despite of this variation exhibit a random pattern. Investigation in a broader spatial scale may help to elucidate the patterns of variation in the songs of the four species here studied.