Vortrag, 8th Biennial Conference of The International Biogeography Society, Tucson, AZ: 09.01.2017 - 13.01.2017
A mechanistic understanding of plant invasion, especially in relation to how climatic conditions control these processes, is still missing. We develop and test a theoretical framework called hierarchical climatic filtering that captures the principles of changing hierarchies of abiotic factors in driving plant invasion. We expect a gateway filter to drive alien establishment by selecting species with climatic requirements overlapping the gateway region. Then a system imminent filter acts along climatic gradients structuring alien niche widths within an island. Both filters select for alien generalists by favoring large niche widths due to the increased likelihood of generalists to overcome the gateway filter. Once established alien generalists are able to spread into other climatic conditions within the island, while this is not the case for alien specialists adapted to the gateway conditions. We test these assumptions by using thirteen elevational transects on windward and leeward sides of six high elevation islands. Understanding the basic mechanisms of plant invasions might help predict future invasions on islands, which are particularly vulnerable to human-induced alterations.