Rapid northwards expansion of a forest insect pest attributed to spring phenology matching with sub-Arctic birch

Abstract

Species range displacements owing to shifts in temporal associations between trophic levels are expected consequences of climate warming. Climate-induced range expansions have been shown for two irruptive forest defoliators, the geometrids Operophtera brumata and Epirrita autumnata, causing more extensive forest damage in sub-Arctic Fennoscandia. Here, we document a rapid northwards expansion of a novel irruptive geometrid, Agriopis aurantiaria, into the same region, with the aim of providing insights into mechanisms underlying the recent geometrid range expansions and subsequent forest damage. Based on regional scale data on occurrences and a quantitative monitoring of population densities along the invasion front, we show that, since the first records of larval specimens in the region in 1997-1998, the species has spread northwards to approximately 701N, and caused severe defoliation locally during [2004][2005][2006]. Through targeted studies of larval phenology of A. aurantiaria and O. brumata, as well as spring phenology of birch, along meso-scale climatic gradients, we show that A. aurantiaria displays a similar dynamics and development as O. brumata, albeit with a consistent phenological lag of 0.75-1 instar. Experiments of the temperature requirements for egg hatching and for budburst in birch showed that this phenological lag is caused by delayed egg hatching in A. aurantiaria relative to O. brumata. A. aurantiaria had a higher development threshold (LDT A.a. 5 4.71 1C, LDT O.b. 5 1.41 1C), and hatched later and in less synchrony with budburst than O. brumata at the lower end of the studied temperature range. We can conclude that recent warmer springs have provided phenological match between A. aurantiaria and sub-Arctic birch which may intensify the cumulative impact of geometrid outbreaks on this forest ecosystem. Higher spring temperatures will increase spring phenological synchrony between A. aurantiaria and its host, which suggests that a further expansion of the outbreak range of A. aurantiaria can be expected.

How can forage production in Nordic and Mediterranean Europe adapt to the challenges and opportunities arising from climate change?

“…The distribution of many weeds, pests and pathogens are limited to the north by harsh winters. With global warming, many of these species can be expected to spread northward (Jepsen et al, 2011;Juroszek and von Tiedemann, 2013;Svobodová et al, 2014).…”

Moth herbivory enhances resource turnover in subarctic mountain birch forests?

“…Global climatic change is predicted to cause changes that will occur more rapidly in the subarctic and arctic areas compared to the rest of the world. Further, a wider dispersal of novel insect herbivores is predicted to increase the risk of severe damage to the region's plant communities (Jepsen et al 2011). In the present study, we investigated soil biological and chemical properties along moth herbivory gradients in subarctic mountain birch forests.…”

Future changes in the supply of goods and services from natural ecosystems: prospects for the European north

“…For example, warmer weather may increase forest pests such as pathogens, diseases, invasive herbivorous insects, and plants (Niemelä et al 2001, Wolf et al 2008b, Valtonen et al 2011. In northern Fennoscandia, northward expanding geometrid moth outbreaks have caused massive devastation of subarctic birch forests (Jepsen et al 2011), most likely owing to warmer winters and springs (Jepsen et al 2008(Jepsen et al , 2011. Climate change is also expected to lead to more severe winter storms and icing events (Chapin et al 2007).…”