The effects of grassland ecosystem afforestation on avian phylogenetic diversity, taxonomic diversity and evolutionary distinctiveness

Forest plantations are among the main threats to the grassland ecosystems of southeastern South America. One key question is whether such plantations affect the evolutionary diversity of bird communities, since previous studies have shown a reduction in taxonomic and functional diversity. High levels of phylogenetic diversity can ensure the conservation of communities, and high evolutionary potential to adapt to environmental changes. Taking this into account we investigated whether the conversion of native grasslands into forest plantations impacted the evolutionary and taxonomic diversity of bird communities, through an analysis of the different dimensions of diversity. Our investigations took place in southern Brazil where native grasslands predominate, however many have been afforested in recent years. We collected data from bird communities in native grassland and forest habitats, as well as from eucalyptus plantations. Our results did not detect a reduction in phylogenetic diversity in the planted areas but did demonstrate the taxonomic impoverishment of bird communities. Furthermore, we registered a reduction in the evolutionary distinctiveness of bird communities in forest plantations and a variation of phylogenetic composition among habitats. This indicates the evolutionary adaptations of species to their habitat, whether it is forest or grassland. Riparian forest lineages appeared more capable of colonizing forest plantations, while grassland lineages appeared unfit to do so. Afforestation of grassland ecosystems may represent a future threat to the maintenance of evolutionarily distinct bird species, as well as to strict grassland species which have been shown to be evolutionarily unable to colonize forest plantations. We recommend the maintenance of forest plantations only in areas that have already been converted or degraded. Additionally, we emphasize the importance of practicing non-intensive economic activities in these areas, for example, cattle production in low-intensity. Such activities in low-intensity have been shown to be beneficial for the maintenance of the evolutionary and taxonomic diversity of bird communities.