The role of native species as biome resistance factors on molasses grass (Melinis minutiflora Beauv.) invasion in rupestrian fields in Minas Gerais State, Brazil

Abstract

Exotic species can spread in the environment, act as an invasive, occupy a niche that was of native species before and replace their role. The impacts caused by invasive species on the native ones show in many ways: decreasing species richness and abundance of native biota, and reducing their local species diversity. In Minas Gerais State, Brazil, a particular kind of vegetation occurs associated with rich iron ore, composed mostly by grass species with representatives of Fabaceae, Asteraceae, Loganiaceae and Malpiguiaceae plants, among others. The native legume Periandra mediterranea (Vell.) Taub. is found spread at the area coexisting with native and alien species. The Parque Estadual Serra do Rola Moça (PESRM) is one of the main strongholds for rupestrian fields preservation and has been suffering gradual invasive process by the African grass Melinis minutiflora Beauv. what has favored fire incidence. Plants can reveal resistance to invading species population growth and works as barrier. In our work we studied the effects of the invasive grass M. minutiflora on plant community and their resistance to invasion in order to subsidize the management of the invasive species M. minutiflora. To evaluate these effects we analyzed: relative frequency of species and families, community richness and composition. We could see a clear resistance to invasion by vegetal community at the lowest levels of occupancy by M. minutiflora as shown by the species: Sporobolus aeneus (Poaceae), Chamaecrista secunda (Fabaceae), Paspalum polyphyllum (Poaceae), Peixotoa tomentosa (Malpiguiaceae), Achyrocline satureioides (Asteraceae) and Periandra mediterraneae (Fabaceae). The latter was a key element for this resistance; having its presence inhibited only when the alien grass became dominant. The data of this study is very important to understand the impacts of invasion and the mechanisms of resistance presented by rupestrian fields at PERSM, showing the negative effects of M. minutiflora on native plant species diversity and also suggesting the resistance and tolerance of P. mediterranea at initial invasion phase.