Divergent introduction histories among invasive populations of the delicate skink (<i><scp>L</scp>ampropholis delicata</i>): has the importance of genetic admixture in the success of biological invasions been overemphasized?

Abstract

Abstract Aim Invasive species are predicted to experience a reduction in genetic diversity during the introduction process because of founder effects, yet they are able to successfully establish in new regions and outcompete the native biota. Admixture has been proposed as a potential solution to this genetic paradox. We adopted a phylogeographic approach to investigate the invasion history of the delicate skink ( L ampropholis delicata ) in the P acific region and test the hypothesis that admixture is important for the success of biological invasions. Location Eastern A ustralia and the P acific region ( L ord H owe I sland, N ew Z ealand, H awaii). Methods We obtained mitochondrial DNA sequence data ( ND 2 , ND 4 ) from across the native Australian range (238 samples, 120 populations) and 371 samples from the introduced range of L . delicata . Genetic distances and Analysis of molecular variance ( AMOVA ) were used to examine the level of genetic variation across the native and introduced ranges. Results Fourteen haplotypes were evident in the introduced range (1 in H awaii, 7 in N ew Z ealand, 7 in L ord H owe I sland), with a shared haplotype present in both N ew Z ealand and L ord H owe I sland. Five source regions were identified ( B risbane, T enterfield, B order R anges, Y amba‐ C offs H arbour, S ydney) from across four distinct native‐range genetic lineages. The H awaiian population stems from a single introduction from B risbane, whereas one or more introductions from the T enterfield region led to the N ew Z ealand populations. Multiple introductions from across all five source regions have resulted in extreme admixture (up to 8.3% sequence divergence) within L ord H owe I sland. Main Conclusions L . delicata introductions are capable of being successful both in the presence and absence of admixture. Contrary to the predictions of the sequential two‐step model, the presence of admixture was not related to the time since initial introduction. We suggest that the importance of admixture in determining the success of biological invasions has been overemphasized.