Drivers of asymmetrical insect invasions between three world regions

Abstract

The geographical exchange of non-native insects can be highly asymmetrical, with some world regions 'exporting' or 'importing' more species than others. Several hypotheses have been proposed to explain such asymmetries, including differences in propagule pressure, environmental features in recipient regions, or biological traits of invaders. We tested aspects of these hypotheses in the context of the exchange of non-native insects between North America, Europe, and Australasia. Europe was the dominant exporter of non-native insect species between the three regions, with most of this asymmetry arising prior to 1950. The European dominance could not be explained by differences in import value, source species pool sizes, or native plant richness in the recipient regions. We identified that the introduction of non-native plants, driven in part by European colonization, best explains the asymmetrical exchange of non-native insects between our focal regions.

Global flows of insect transport and establishment: The role of biogeography, trade and regulations

“…Yet flows of established species were on average greatest for flows originating from the Western Palearctic, Neotropical and Australasian and Oceanian regions. Similarly, Isitt et al (2023) found that Europe (i.e. the Western Palearctic) was the dominant source of established non‐native insects between North America, Europe and Australasia.…”

“…As well as increasing opportunities for introduction, greater trade intensity could improve the chances of species establishing through repeated introductions (Lockwood et al, 2005). Isitt et al (2023) further found no evidence for the hypothesis that a larger pool of native species leads to proportionally more species being exported. However, the history of European colonization in North America, and Australia and New Zealand may have obscured the impact of native species pool size.…”

“…While the effect of broad socio‐economic variables like GDP or GNI on establishment success is debated (Brenton‐Rule et al, 2016; Sharma et al, 2010; Westphal et al, 2008), more precise measures, such as the value of relevant commodity imports, appear to be better predictors of invasion risk for unintentionally introduced taxa (Ollier & Bertelsmeier, 2022). Isitt et al (2023) conclude that plant introductions driven by European colonization is the most compelling explanation for the invasion asymmetry they observed, while native species pool sizes and total import values have little effect. The contrasting influence of trade value in our study may be due to using import values for plant products, a key insect introduction pathway (Fenn‐Moltu et al, 2022; Kiritani & Yamamura, 2003; Liebhold et al, 2012; Meurisse et al, 2019), rather than total import values to predict establishments and using trade value per commodity type at the transport stage.…”

Distribution, Invasion History, and Ecology of Non-native Pine Bark Beetles (Coleoptera: Curculionidae: Scolytinae) in Southern South America

“…2017; Corley et al 2020; Vilardo et al 2022).An interesting nding of our study is that, although the native pool of pine bark beetles from North America is similar to the one of Eurasia(Wood and Bright 1992), the six pine bark beetle species established in South America are native to Europe and/ or Asia. This patterns of "invasion asymmetry", where the Palearctic region is over-represented and the Nearctic region under-represented as donors of non-native established species, has been commonly observed in forest insects(Mattson et al 2007;Lantschner et al 2020;Isitt et al 2023). There is no clear explanation for this pattern in our case, since the Nearctic and Palearctic regions have been historically strongly connected with the Neotropical region via trade(Lantschner et al 2020), both regions have considerable areas with similar climatic conditions differences in the evolutionary pressures between regions(Mattson et al 2007), or because of the small size of our sample.…”