Novel spatial analysis methods reveal scale-dependent spread and infer limiting factors of invasion by Sahara mustard

scale analyses are essential for revealing how the infl uence of specifi c ecological factors changes with scale (Wiens 1989). In this study, we present a novel methodology that can be broadly-applied to assess the scale-dependency of species ’ distributions. Distribution changes – such as those that occur in response to species introductions or climate change – provide ecological experiments that can reveal the factors that set range boundaries at specifi c scales (Holt et al. 2005, Kinlan and Hastings 2005, Pysek and Hulme 2005, Ricklefs 2005, Sexton et al. 2009). Increasing number of studies have assessed the distribution of invasive species across multiple spatial scales. Most of them emphasize on how current extent of invasion changes with spatial scales (Foxcroft et al. 2009) and what ecological factors are associated with this scale dependency of existing invasion extent (Catford et al. 2009, Akasaka et al. 2012). But very few (Lonsdale 1993, Pysek et al. 2008) have examined how historical and current rate of range expansion change with spatial scales. It is important to reveal the temporal dynamics of scale dependent range expansion in order to infer historical and existing ecological factors that may infl uence distribution changes at specifi c scales. We suspect the lack of such study is largely due to methodological barrier. Here we illustrate the use of the Ecography 38: 311–320, 2015 doi: 10.1111/ecog.00722 © 2014 Th e Authors. Ecography © 2014 Nordic Society Oikos Subject Editor: Timothy Keitt. Accepted 25 June 2014