Canadian Forest Service Publications
Climate change can reduce the risk of biological invasion by reducing propagule size. 2017. Gray, D.R. Biological Invasions 19(3): 913–923.
Issued by: Atlantic Forestry Centre
Catalog ID: 39556
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Climate change has been conclusively linked to species extinctions, and to expansion and contractions and shifts of species ranges. Climate change is exerting similarly profound pressures on the individual stages of biological invasion which can significantly impact the biodiversity and ecology of invaded areas. Propagule pressure is perhaps the single most important determinant of invasion success, but the effects of climate change on propagule pressure are still largely uncertain because we have few observations of introduction events (or their size) that can be analyzed together with climate records. The common surrogate variables for propagule pressure do not logically respond to climate. Here I use a process-based simulation model to examine the potential effects of climate change (specifically temperature) on propagule size of a common invading insect species by estimating in-transit survivorship rate of propagules using historical and future (projected) temperatures and two common trade routes between a donor and a recipient location (Yokohama, Japan and Sydney, Australia). Propagule size (=the number of individuals in an introduction event) was lower under climate change temperatures than under historical temperatures in both routes. The route had significant effects on propagule size through its influence on the duration (and also the timing) of exposure to temperature conditions that are of time-sensitive importance to the development of the invasive species. Under historical temperatures propagule size was higher and less variable in the direct than the indirect route in 20 independent iterations. Under the future temperatures propagule size was also higher in the direct route but it was more variable than in the indirect route. Increased trade is increasing the opportunities for introductions, but the results reported here suggest that climate change will have inconsistent effects on biological invasion because of the complex relationship between temperature and insect ontogeny.
Plain Language Summary
The Asian gypsy moth (AGM) is an alien invader whose usual method of introduction is via long-distance, international marine trade. Adult female AGM are attracted to the artificial lights in ports and deposit their egg masses on the containers and superstructures of vessels. Introductions of AGM occur when larvae emerge from the egg masses after arrival at the destination. Larval emergence will occur only after the egg masses have been exposed to a temperature regime that satisfies the complex requirements of embryonic development. The marine route between the port source and the port destination of an introduction affects the temperature conditions to which the transported egg masses are exposed, and therefore the viability of the onboard population of developing embryos. Computer simulations indicate that embryos that are transported directly from Japan to Australia (and which, therefore, experience a rapid and unnatural change in season and temperature regime) are not negatively affected, and larval emergence in Australia from an onboard population is high. An indirect route (via Alaska and Canada) can have negative consequences for the developing embryos. Successful development of onboard embryos is negatively affected by the warmer temperatures of a future climate scenario, regardless of the route.