Contemporary range expansions are often simply attributed to global change (Hickling et al. 2006), but instead might be caused by a complex interplay of factors. A combination of global change, ecological processes, phenotypic plasticity, and finally adaptation might pave the way for the currently observed massive expansions of many species (Gienapp et al. 2008; Franks and Hoffmann 2012). This might also hold true for the yellow sac spider. Warming climate and the increasing availability of fallow land could have initially enabled an expansion into novel habitats. The expansion did not occur on a broad front. Instead, several suitable patches of habitat were colonized outside of the native range. First isolated occurrences of the yellow sac spider were in fact reported from northeastern Germany in the mid‐20th century (Muster et al. 2008). Like many other spiders, C. punctorium probably possesses high dispersal ability, due to passive, wind‐mediated ballooning of young spiderlings (Bell et al. 2005; Krehenwinkel et al. 2016). The range wide homogeneity of 28S rDNA and overall low microsatellite differentiation within the native range also suggests connectivity of populations by gene flow. Suitable emerging habitat and changing temperatures can probably be quickly reached by the species.