Invasion tolerance varies along a topographic gradient irrespective of invader presence

Invasive exotic plants often impact native plant species through strong competition, yet their effects can vary across different native populations. Previous exposure to invasive species but also differentiation along abiotic gradients may determine to what extent native populations are competitively suppressed by plant invasive species. Here, we experimentally investigated whether competitive effects of the invasive exotic jewelweed Impatiens parviflora on its native congener Impatiens noli-tangere are related to previous exposure to the invader or rather to topography of the source populations, i.e., to terrain features such as elevation, aspect, or slope. We also asked whether, in return, topographic settings of invasive I. parviflora populations may explain competitive effects of the native jewelweed. In a common garden competition experiment we found that populations of native jewelweed from colder, higher altitude sites and from drier sites were on average seven and six times, res..., ,