IMPACTO DE MELINIS MINUTIFLORA (POACEAE) EN LA DIVERSIDAD DE PLANTAS VASCULARES DE PASTIZALES DE LAS ARENISCAS DE MISIONES (ARGENTINA).

Background and aims: The invasion of natural ecosystems by alien species represents a major concern in the context of global conservation. In the fields of Teyú Cuaré, in the department of San Ignacio, Misiones, there is a high level of endemism with at least eight species of microendemic vascular plants. These grasslands are considered the only Cerrado fragments present in Argentina and are being invaded by Melinis minutiflora (Poaceae). The aim of this work was to evaluate how this adventitious grass affects the composition and diversity of the vegetation, and to determine the progress in the period 2015-2017. M&M: To measure the impact, the vegetation was sampled using 25 random plots of 1x1m in areas with and without invasion. Phytosociological parameters and diversity indices were calculated. For the measurement of progress, perimeter walks were carried out with GPS. Results: We found that areas free of this exotic grass had a higher total number of species (81), and a higher number of species exclusively present only in these sites (51). The area analysis showed an increase from approximately 9,744 m² to 23,396 m². Conclusions: Our results indicate that the advance of M. minutiflora populations is vertiginous and that it exerts a significant pressure on grassland structure and diversity by occupying the ecological niche of native herbs and subshrubs. [ABSTRACT FROM AUTHOR]