Ecology of an invasive plant, Senecio inaequidens : interactions with pollinators, herbivores and soil fauna : comparison with the native Senecio jacobaea
(2009)
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- Interactions with animals are thought to play a role in plant invasions, especially herbivores and pollinators. The importance of soil fauna in ecosystem processes is widely acknowledged and some invasive plants have been shown to affect their communities. In this thesis, field observations and experiments in natural or controlled conditions were conducted to investigate the interactions of these three faunic groups with the invasive Senecio inaequidens and the native related species, S. jacobaea. First, both plant species were visited by similar pollinator assemblages but S. inaequidens received more visitors per capitula than S. jacobaea. This difference could not be attributed to nectar or floral display. The reproductive success was higher for S. inaequidens than S. jacobaea, with 78 and 55% seed set respectively. The role of pollinators in seed set was not assessed but the difference between species may not be due to a higher self-fertility of S. inaequidens. Nevertheless, S. inaequidens had no impact on plant-pollinator interactions of S. jacobaea. Second, four out of the five studied herbivores attacked both S. inaequidens and S. jacobaea. The only herbivore restricted to S. jacobaea was the specialist caterpillar Tyria jacobaeae. Nevertheless, S. inaequidens was more impacted by overall herbivory than S. jacobaea, especially at the seedling stage by rabbit grazing. Pyrrolizidine alkaloids (main chemical defences) seem to play no role in the pattern of herbivore preferences. Third, soil arthropods were twice less abundant under S. inaequidens than S. jacobaea, essentially due to collembolan Arthropleona. No difference was found in the community assemblage but S. inaequidens was associated to higher arthropod diversity than S. jacobaea. These findings suggest that the two species interact with similar animal assemblages, but in different ways. The invasive success of S. inaequidens is more probably explained by an efficient reproduction than by a release from herbivores.
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Vanparys, V. (2009). Ecology of an invasive plant, Senecio inaequidens : interactions with pollinators, herbivores and soil fauna : comparison with the native Senecio jacobaea. https://hdl.handle.net/2078.5/124063