Master Thesis

Ecological consequences of invasive woody plants replacing endemic Scalesia cordata trees in the Galápagos Islands

Anna Walentowitz (05/2019-11/2019)

Support: Carl Beierkuhnlein, Severin D.H. Irl

Vegetation communities on islands contain high numbers of endemic species but are transformed by an increasing number of invasive biota. The implications for diversity, native plant communities, as well as single endemic and often severely threatened plant species are poorly understood. However, suchlike information is necessary for a proper understanding of the ongoing changes and essential to develop effective conservation actions. This study combines island biogeography, invasion and conservation biology to shed light on the alteration in plant communities resulting from woody plant invasions at the example of the Scalesia cordata forest in the Galápagos Islands, Ecuador. The study aims at 1) assessing impacts of woody invaders on vegetation compositions and plant species diversity at community level and 2) providing a basis of information about the target area and species for the refinement and development of conservation methods. Most known populations of Scalesia cordata have been replaced by an assemblage of woody invasive plants such as Psidium guajava with the native fern species Nephrolepis biserrata growing in the understory. Plant diversity is being reduced by woody neophytes and plant species compositions differ substantially between S. cordata vegetation communities and vegetation dominated by woody invasives. Promoting and restoring S. cordata forests is essential to stop population decline of this threatened endemic species. In combination with reducing the dominance of P. guajava this could lead to local increases in plant diversity and thus the results of this study call for immediate conservation actions.