Evidence of a climatic niche shift following North American introductions of two crane flies (Diptera; genus Tipula )
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ORIGINAL PAPER
Evidence of a climatic niche shift following North American introductions of two crane flies (Diptera; genus Tipula) Matthew J. Petersen
Received: 4 October 2011 / Accepted: 30 August 2012 / Published online: 11 September 2012 Ó Springer Science+Business Media B.V. 2012
Abstract Ecological niche models assume a species niche should be conserved over space and time. Increasingly, studies have determined that niche shifts may occur during biological invasion events. The aim of this study is to examine niche conservation for two invasive crane flies, Tipula oleracea Linnaeus and Tipula paludosa Meigen, after introductions into North America. These species have broadly sympatric invasive distributions but differ in time since introduction and dispersal abilities. As these factors may impact the area accessible to dispersal, I examined the impact of background area delineation on conclusions of niche conservation. Results indicated that alternative delineations of accessible area (i.e., background area) had no affect on measures of niche equivalence. Neither Tipula species was found to be occupying invasive niche space equivalent to that of their native ranges. Niche dissimilarity was found for both species, with results strongly impacted by the choice of background area. T. paludosa introductions displayed a niche shift across both invasive introductions when the model area drew climatic information from an area that buffered occurrences by 40 km. The eastern T. oleracea introduction displayed a niche shift when background information was drawn from within a 400 km buffered area. This study suggests that
M. J. Petersen (&) Department of Entomology, Cornell University, 630 W. North Street, Geneva, NY 14456, USA e-mail: [email protected]
invasive populations may be displaying a niche shift when evaluated against one scale of background but conserved when evaluated against another scale. Dispersal limitations for T. oleracea in its eastern introduction and anthropogenic habitat associations for T. paludosa across both invasive introductions are indicated as causes for the observed niche shifts. The results of this study highlight the importance of carefully delineating the area accessible to invasive species in studies of niche conservation. Furthermore, it indicates that examining several spatial extents of background areas can be beneficial when examining niche conservation for species in non-equilibrium states. Keywords Invasion biology Ecological niche modeling Maxent Tipula oleracea Tipula paludosa Tipuloidea
Introduction Predicting species distributions using occurrencebased ecological niche modeling (ENM), also called species distribution modeling (SDM), has emerged as an important tool for studying biological invasions (Peterson and Vieglais 2001; Peterson 2003; Thuiller et al. 2005). Predicting species occurrence with ENMs is based on the contention that ecological factors act as constraints on survival and ultimately determine a species’ potential distribution (Hutchinson 1957;
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