Pre-adaptation as a driver of plant invasions in agroecosystems : empirical investigation and theoretical discussion with a historical perspective
In human-altered environments like agroecosystems, invasive plants are particularly harmful due to their adaptation to disturbances from livestock and cultivation. Pre-adaptation to these disturbances might explain their success in such systems. The Neolithic Plant Invasion Hypothesis (NPIH) suggests that European invasive plants are pre-adapted to agropastoralism due to its long history in the region. This thesis tests a key prediction of the NPIH: species with longer exposure to agropastoralism should better withstand its disturbances. I selected invasive species from West Asia (~12000 years), Europe (~8000 years), and America (~5000 years) to compare their responses to agropastoral disturbances. The first experiment studied germination and seedling performance of 30 species under various disturbance levels and space occupancy. While moderate disturbance aided germination, no significant differences were found between the groups. The second experiment involved 45 species, focusing on maturity, reproduction, and fitness. Seedlings were transplanted to a field where soil disturbance and clipping were applied. Over two years, growth and reproduction were monitored, followed by a fitness assessment in a lab. Soil disruption improved growth, while clipping reduced it, but species responses did not clearly correlate with long agropastoral exposure. Fitness differences were seen, but no clear link to historical exposure emerged. These results might reflect modern adaptation or convergent evolution, as agropastoralism has existed in many regions worldwide. Additionally, I reviewed literature on pre-adaptation and its role in invasions, discussing the NPIH and the AIAI hypothesis. With mixed support for NPIH, I explored its historical basis and proposed interdisciplinary approaches, including archaeobotanical research, to study the evolution of invasive plants. Future work on plant invasions should integrate ecological, evolutionary, and socioeconomic perspectives.
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