Impact of globalization on the spread of non-native insects
Bonnamour, A. (2025). Impact of globalization on the spread of non-native insects. PhD Thesis. Université de Lausanne, Faculté de biologie et médecine: Lausanne. 196 pp.
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Document type: Dissertation
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| Abstract |
With increasing global trade, thousands of species have been introduced, intentionally or accidentally, to new regions outside of their native range, and some of them have significant impacts on ecosystems and human societies. A better understanding of the human-mediated dispersal of species is therefore required in order to better predict and prevent future invasions. This thesis investigates the effects of globalization and human activities on the spread of non-native species, with a particular focus on insects, which are very successful and damaging invaders that are mostly transported and introduced accidentally. Chapter 1 addresses the temporal dynamics of insect and plants invasions over the past centuries. We used a statistical model that accounts for temporal variations in sampling effort to estimate insect and plant invasion rates. We found that, once sampling bias is accounted for, the rate of insect and plant invasions did not continuously increase over the past two centuries, but fluctuated, following the two waves of globalization (~1820–1914, 1960-present). In chapter 2, we show that the rise and fall of European colonial empires strongly influenced the spread of non-native species, using ants as a model system. Our results indicate that, before 1960, countries that belonged to a colonial empire received a higher number of non-native ant species than those that did not, and that ants spread preferentially between countries that belonged to the same empire. After 1960, however, former colonial ties no longer had an effect on ant invasions. We also found that most non-native ant species originated from colonized countries, which contrasts with the “Imperialist dogma”. Chapter 3 explores the importance of secondary introductions (i.e., the bridgehead effect) in non-native insect dispersal. We found that 34% of insect interceptions at ports of entry in the United States between 1913 and 1984 originated from previously invaded regions, rather than from the species’ native range. We found that the probability of secondary introduction increased over time, and was also linked to the size of the species’ non-native range. Our results show that the bridgehead effect creates a positive feedback loop between transport and establishment, leading to an acceleration of invasions. Finally, chapter 4 highlights the strong link between plant and insect invasions, and shows that non-native plant flows dating back to 1900 were the best predictor of geographical variation in current non-native insect flows. This time lag between plant and insect invasions leads to a substantial insect invasion debt globally. The estimated debt was most important in the Afrotropics and the Neotropics, suggesting that insect invasions are likely to strongly increase in those regions in the near future. Overall, this thesis improves our understanding of the socio-economic drivers of biological invasions, and highlights the need for more research on the human dimensions of invasions because biological theory alone cannot explain or predict the spread of non-native species. |
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