Distribuição espacial de girinos em uma poça temporária no município de Cruz das Almas, Bahia

Abstract

The interaction between different organisms involves a set of factors that can contribute equally to the coexistence of the different species. Thus, two species may converge or diverge in some dimension of the multidimensional niche avoiding competition. Anurans are animals that require water bodies for reproduction, which increases competition and shapes behavioral and ecological divergences between species through the niche partition. In this study, it was be investigated how the tadpoles species of a temporary pond use the microhabitat, in order to verify the existence of patterns in the use of space that can explain the coexistence. The study was carried out in a temporary pond located in the Cruz das Almas, Municipality, Bahia State, inserted in the Atlantic Forest biome. The pond was divided into five Stations and fifteen Substations. For each Substation, the temperature, depth and abundance of tadpoles of different species were measured. After, the niche width and niche overlap were calculated by Stations and Substations. A null model analysis was used to determine the presence of patterns in the use of space. Finally, a Correspondence Analysis was used to verify preferences in the use of space between species, considering the Stations and Substations. Were found 605 individuals of seven species. The distribution of tadpoles was restricted to Stations 3, 4 and 5. The analysis of niche width showed that the species Boana faber was the most generalist (2.71), while Physalaemus cuvieri was the most especialist (1.0). Overlapping values ranged from 98.1% to 3.8%, with the highest values found between Scinax x-signatus and Dendropsophus elegans (0,981) and Boana albomarginata and Boana faber (0,974). The null model analysis showed observed mean of 63% and expected of 66%, not evidencing the presence of patterns (p = 0.32). For substations, the niche width ranged from 1.0 to 6.3, with B.faber (6.33) and D. oliveirai (4.61) showing the highest values and P. cuvieri (1.0) and S. x-signatus (1.81) the smallest. Overlapping values ranged from 93.1% to no overlapping, with the highest value observed between B. albomarginata and B. faber (0,931) e B. albomarginata and S. x-signatus (0,927). The analysis with null model revealed an observed mean overlap of 40% and expected of 45%. Comparisons between the means showed not structure in the position that the species occupy in the temporary pond (p = 0.12). Nevertheless, comparisons between means of variance showed significant results (p = 0.001). The correspondence analysis by Station revealed preference of the species in use of microhabitats with more plants, and the analysis by Substations revealed that species group showed preference for specific positions in the pond. Tadpole showed preference for microhabitat with predominance of vegetation, lower temperatures and lower depth. The absence of structure in the position within the temporary puddle and formation of guild refer to the existence of the historical mechanism regulating the use of space.