Abstract:
Globalization is triggering an increase in the establishment of alien insects in Europe, with several species having substantial ecological and
economic impacts. We investigated long-term changes in rates of species spread following establishment. We used the total area of countries
invaded by 1171 insect species for which the date of first record in Europe is known, to estimate their current range radius
(calculated as [invaded area] /π). We estimated initial rates of radial spread and compared them among different groups of insects for
all years (1800–2014) and for a subset of more recent decades (1950–2014). Accidentally introduced species spread faster than
intentionally introduced species. Considering the whole period 1800–2014, spread patterns also differ between feeding guilds, with
decreasing spread rates over residence time in herbivores but not in detritivores or parasitic species. These decreases for herbivorous
species appeared mainly in those associated with herbaceous plants and crops rather than woody plants. Initial spread rate was
significantly greater for species detected after 1990, roughly 3–4 times higher than for species that arrived earlier. We hypothesize that the
political changes in Europe following the collapse of the Iron Curtain in 1989, and the further dismantling of customs checkpoints within an
enlarged European Union (EU) have facilitated the faster spread of alien insect species. Also, the number of species first recorded in the
Eastern Bloc of the politically-divided Europe before 1989 was lower than for the rest of Europe. A detailed analysis of six recent invaders
indicated a dominant role of long-distance translocations related to human activities, especially with the plant trade, in determining rates of
spread.
Description:
This paper had its origin at a workshop on “Drivers, impacts, mechanisms and adaptation in insect invasions” hosted and co-funded by the
DST-NRF Centre of Excellence for Invasion in Stellenbosch, South Africa, in November 2014.