A infestação por uma liana invasora interfere na interação entre aves e uma palmeira nativa?

Abstract

The interactions between plants and birds are essential for both, since there is a mutual supply of resources. With the help of birds, plants can pollinate its flowers and disperse its seeds. In its turn, plants are important because they can provide food and places where birds can nest. The carnaúba (Copernicia prunifera) is an endemic plant from Brazil that is very important to the ecosystem and to the local income and it’s currently threatened by the presence of the invasive vine viúva-alegre or unha-do-diabo (Cryptostegia madagascariensis). In this context, the purpose of this research is to understand how the invasion by viúva-alegre can impact the interactions between the native plant and the birds. The study was placed in an area in the city of Caridade, in the district of Várzea Redonda. Individuals of carnaúba were marked with spray paint and information about the native plant individual’s height and the degree of infestation of the plants were measured. Furthermore, 22 observation points were selected systematically along trails in the study area. The carnaúbas inside the observation points were observed for 10 minutes and the interactions were recorded in a spreadsheet. The information about the birds’ species, the behavior exhibited, the type of resource and the plant’s structure that were used were all recorded. Data analysis was performed in the R program and the Poisson regression model was conducted, using the general linear model (GLM) to verify if the infestation interfered in the abundance and species richness that interacted with the carnaúbas. A Principal Coordinates Analysis (PCoA) was also applied to investigate differences in the composition of species that interacted in carnaúbas with and without infestation. The chi-square test was applied to investigate whether there was a difference in the way birds behaved, in the type of resources and in the plant’s part used. Throughout the study 28 bird species interacted with carnaúba, and there was no difference in the composition of species that visited the two types of carnaúba. The degree of infestation did not influence abundance and species richness. There was no difference between the types of behaviors exhibited, the type of resources and the native plant’s structures used in carnaúbas with different degrees of infestation. Although the presence of the invasive liana do not significantly interfere in the way the species interact with carnaúbas, birds tend to use the resources of the native plant more. The main type of resource used at the period of the year the study was conducted was a place to perch. This may have been caused by the lack of carnaubas with fruits and possibly because of the insufficient arthropods’ abundance in the infested carnaúbas due to the dry weather. Thus, the degrees of infestation studied showed no influence on the interaction between birds and carnaúbas, however it’s important to verify in future studies if this is also the case in periods when the carnaúba bears fruits.