Personality shifts are inconsistent across two rapid range expansions of a non-native spider

Abstract

Successful biological invasions are characterized by the spread of a population across a landscape. Range expansion conditions can favour different phenotypes at the leading edges of the range compared to those at the core. Although Cyrtophora citricola is a non-native spider species that was documented in Florida, U.S.A. almost two decades ago, the status of its populations remains unstudied. We report two populations that have spread northward along both eastern and western coasts from a putative common origin. We asked whether the leading edges of these two range expansions are composed of different personality types compared to the original core and whether core-to-edge patterns in personality are consistent between the two replicate populations. More voracious, more exploratory and bolder spiders were predicted to occupy the leading edge, because these personality types are assumed to be associated with dispersive, successful colonizers in novel environments. While leading-edge spiders were indeed faster to respond and attack prey stimuli and active longer in novel environments compared to spiders from the core, the two populations diverged in boldness. On average, western spiders were less bold and exploratory towards newer colonization sites, whereas eastern spiders were bolder at newer sites. The divergence in exploratory behaviour and boldness between these populations highlights the difficulties in generalizing how traits may become assorted across an expanding range and stress the importance of using replicate populations when possible. These results suggest that range level processes can be inconsistent and highlight the importance of investigating how the strength of local adaptation may swamp processes such as spatial sorting.