Temperature explains variable spread rates of the invasive woodwasp Sirex noctilio in the Southern Hemisphere

Abstract

The frequency of introductions of non-indigenous forest insects into new habitats is increasing worldwide, often with profoundly adverse consequences on natural and plantation forest ecosystems. Understanding rates and patterns of spread of invasive forest insects is important for predicting when and where these species will expand their geographical range, with the potential to improve mitigation strategies. The woodwasp Sirex noctilio is a damaging invasive forest insect 2 that kills numerous species of Pinus. Despite encountering highly variable eco-climatic conditions, S. noctilio has arrived and established in exotic pine forest production areas throughout the Southern Hemisphere. In this study, we compiled historical records of S. noctilio invasion to compare spread rates among eight contrasting eco-climatic regions in the Southern Hemisphere and to explore how spread rate is predicted by landscape variation in climate, habitat characteristics, and anthropogenic effects. Spread rates for S. noctilio varied considerably among the invaded regions, ranging from 12 to 82 km per year. Among regions, spread rates of S. noctilio increased with increasing mean annual temperature and isothermality. We hypothesize that temperature may directly or indirectly influence S. noctilio population growth and dispersal, thereby influencing spread rates.

Forest Insects and Climate Change

“…Of these, two non-native insects that became invasive in various parts of the world, the emerald ash borer, Agrilus planipennis [53], and the Sirex woodwasp, Sirex noctilio [76], have large expansion potential in their newly invaded areas. Human-mediated transportation has been attributed to have facilitated the expansion of A. planipennis in the USA.…”

Range-Expanding Pests and Pathogens in a Warming World

“…For example, subnational historical observations allowed the rates of spread of the invasive woodwasp Sirex noctilio across parts of South America, South Africa, and Australia to be related to high-resolution climate data, showing that dispersal rate increased with mean annual temperature and isothermality (78). The most intense spatiotemporal monitoring of any plant disease is the US network of soybean sentinel plots for soybean rust (Phakopsora pachyrhizi ) (158).…”

SirexWoodwasp: A Model for Evolving Management Paradigms of Invasive Forest Pests

“…Much remains to be learned about the ecology of the multiple components of mutualistic and parasitic interactions that either facilitate or restrict the development of S. noctilio populations. Substantial new insights are likely to arise from comparative studies across systems in different parts of the world, as has been well illustrated in recent studies on the spread, biology, and ecology of the wasp (4,10,21,64). Such information will be invaluable in the quest to refine and sustain management programs around the world.…”

“…The spatial dynamics, including both aggregation and flight potential, of S. noctilio populations represent important issues in understanding the development and spread of outbreaks (16,24,25,64,117). Such studies showed increasing spatial aggregation under preoutbreak and outbreak conditions, which became less evident as the outbreak developed (25, 117) (Supplemental Table 1 Table 1).…”