Influência do tipo e tamanho dos fragmentos de Hydrilla verticillata sobre sua capacidade de colonização e regeneração e efeito da densidade de uma macrófita aquática nativa sobre seu potencial invasor.

Abstract

Invasive species are widely recognized as responsible for biodiversity loss around the world, representing one of the most serious challenges for the protection of natural ecosystems and the services they provide. Hydrilla verticillata, is an example of highly invasive species that has caused ecological and economic problems in many aquatic environments around the planet. Recently, this species was registered in the upper Parana river floodplain system UPRFS, and evidence suggests that this exotic can compete with native species of same family Hydrocharitaceae, Egeria densa and E. najas. Little is known about the effects of this species on native population of the UPRFS. Thus, this study is divided into two chapters that attempt to improve understanding of the factors that may affect the invasiveness of H. verticillata. The first consisted of an investigation of the potential of colonization, regeneration and relative growth rate of different types and sizes of fragments of this species, since fragmentation plays a key role of vegetative dispersal. Thus, identify which fragments are more efficient in colonize and regenerate may have important implications regarding the adequate control and management. Nowadays, many studies have focused on species diversity as an attribute that can provide a greater resistance to invasion by exotic species. However, studies indicate that there are positive and negative correlations between species richness and invasion. Alternatively, the invasiveness can be reduced by density of native species. Thus, the second chapter aims to assess if the density of a native population of an aquatic macrophyte may limit the invasiveness of an exotic species. From the results, we wish to expand the knowledge about this exotic species in the environment that have been recently invaded for it.