Escape from natural enemies during climate‐driven range expansion: a case study

Abstract

. 1. A major, and largely unexplored, uncertainty in projecting the impact of climate change on biodiversity is the consequence of altered interspecific interactions, for example between parasitoids and their hosts. The present study investigated parasitism in the Brown Argus butterfly, Aricia agestis ; a species that has expanded northward in Britain during the last 30 years in association with climate warming.2. Aricia agestis larvae suffered lower mortality from parasitoids in newly colonised areas compared with long-established populations. This result was consistent over four consecutive generations (2 years) when comparing one population of each type, and also when several populations within the historical and recently colonised range of the species were compared within a single year. Thus, A. agestis appears to be partially escaping from parasitism as it expands northwards.3. Reduced parasitism occurred despite the fact that several of the parasitoid species associated with A. agestis were already present in the newly colonised areas, supported predominantly by an alternative host species, the Common Blue butterfly, Polyommatus icarus .4. As the species expand their distributions into areas of increased climatic suitability, invasion fronts may escape from natural enemies, enhancing rates of range expansion. The results suggest that the decoupling of interspecific interactions may allow some species to exploit a wider range of environments and to do so more rapidly than previously thought possible.Key words . Aricia agestis , butterfl y , climate change , enemy escape , parasitoids , range expansion . [413][414][415][416][417][418][419][420][421] have not been explored in relation to climate change, and the outcome could be quite different in this context. The biological invasions literature has largely considered species that have been transported long distances by humans, and that have left some or all of their natural enemies behind ( Clay, 2003;Mitchell & Power, 2003;Torchin et al. , 2003 ; Gröbler & Lewis, in press). Such invasive species will often be taxonomically or biologically distant from native species in the area under invasion, so natural enemies may not switch quickly to the invading host or prey. In contrast, natural enemies might be able to track species expanding their distributions in response to climate change much more effectively, given that the initial distribution change does not usually involve long-distance movement away from the long-standing geographic range, and that related species harbouring shared natural enemies may already occur in the regions of expansion.The present study tests the hypothesis that a species that has moved northwards as the climate has warmed has escaped from its natural enemies. Materials and methods The study systemThe study organisms were the Brown Argus butterfly [ Aricia agestis (Denis and Schiffermüller)] and its parasitoids. Aricia agestis has expanded its distribution northwards in Britain, moving at about 10 km per year since the early...

Temporal and spatial variations in the parasitoid complex of the horse chestnut leafminer during its invasion of Europe

“…However, they considered the former to be more important, among other reasons because of fast host switches in some parasitoids, the low host specificity of the examined parasitoid complex in general and the fact that species richness gradients with latitude had already been demonstrated before (Noyes 1989). Menéndez et al (2008) also found declining parasitism rates in the butterfly Aricia agestis (Denis and Schiffermüller) with increasing latitudes and decreasing host residence times in the UK. In contrast to Gröbler and Lewis (2008), however, parasitism richness did not show the same trend and closely related native butterflies were heavily attacked at the newly colonized northern boundaries of the range of A. agestis.…”

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Does including physiology improve species distribution model predictions of responses to recent climate change?

“…This expansion may have been enabled by a reduction in thermal stress and may have resulted in range boundaries better corresponding to absolute physiological limits. Additionally, range expansion may have been facilitated by an escape from parasitism (Mene´ndez et al 2008). Life history trade-offs can result in different range constraints acting across a range and complicate predictions of range dynamics (Burke et al 2005).…”