Independent introductions and sequential founder events shape genetic differentiation and diversity of the invasive green anole (Anolis carolinensis) on Pacific Islands

Abstract

Aim: Natural range expansions and human-mediated colonizations usually involve a small number of individuals that establish new populations in novel habitats. In both cases, founders carry only a fraction of the total genetic variation of the source populations. Here, we used native and non-native populations of the green anole, Anolis carolinensis, to compare the current distribution of genetic variation in populations shaped by natural range expansion and human-mediated colonization.Location: North America, Hawaiian Islands, Western Pacific Islands. Methods:We analysed 401 mtDNA haplotypes to infer the colonization history of A.carolinensis on nine islands in the Pacific Ocean. We then genotyped 576 individuals at seven microsatellite loci to assess the levels of genetic diversity and population genetic differentiation for both the native and non-native ranges.Results: Our findings support two separate introductions to the Hawaiian Islands and several western Pacific islands, with subsequent colonizations within each region following a stepping-stone model. Genetic diversity at neutral markers was significantly lower in the non-native range because of founder effects, which also contributed to the increased population genetic differentiation among the non-native regions. In contrast, a steady reduction in genetic diversity with increasing distance from the ancestral population was observed in the native range following range expansion.Main conclusions: Range expansions cause serial founder events that are the spatial analogue of genetic drift, producing a pattern of isolation-by-distance in the native range of the species. In human-mediated colonizations, after an initial loss of genetic diversity, founder effects appear to persist, resulting in overall high genetic differentiation among non-native regions but an absence of isolation-by-distance. Contrasting the processes influencing the amount and structuring of genetic variability during natural range expansion and human-mediated biological invasions can shed new light on the fate of natural populations exposed to novel and changing environments. K E Y W O R D SAnolis lizards, founder effects, human-mediated colonizations, islands, microsatellites, mtDNA, range expansion | 667 MICHAELIDES Et AL.

An island‐hopping bird reveals how founder events shape genome‐wide divergence

“…The relatively minor impact of single founder events on silvereye genetic diversity and divergence, compared to the obvious TA B L E 3 Best parameter estimates from demographic modelling implemented in fastsimcoal2. cumulative effects of sequential founder events, supports theoretical (Le Corre & Kremer, 1998) and experimental (Bryant & Meffert, 1993) expectations, along with results from a small number of microsatellite studies of sequential colonization in the wild (Lambert et al, 2005;Michaelides et al, 2018;Pruett & Winker, 2005;Thulin et al, 2011),…”

“…The relatively minor impact of single founder events on silvereye genetic diversity and divergence, compared to the obvious cumulative effects of sequential founder events, supports theoretical (Le Corre & Kremer, 1998) and experimental (Bryant & Meffert, 1993) expectations, along with results from a small number of microsatellite studies of sequential colonization in the wild (Lambert et al, 2005; Michaelides et al, 2018; Pruett & Winker, 2005; Thulin et al, 2011), including a microsatellite study of the silvereye (Clegg, Degnan, Kikkawa, et al, 2002). The greater power and precision provided by the large number of SNPs used here convincingly shows that the erosion of diversity with population founding stems primarily from loss of rare alleles during the colonization process.…”

Admixture of hybrid swarms of native and introduced lizards in cities is determined by the cityscape structure and invasion history

“…It is defined as 'reproduction between members of genetically distinct populations, producing offspring of mixed ancestry', which applies to both inter-and intraspecific interactions [35]. While founder effects usually increase genetic drift and differentiation caused by a loss of genetic diversity [36], hybridization increases genetic diversity [37]. Depending on hybrid fitness, fitness of parental taxa and relative hybrid abundances, hybridization can result in heterosis and adaptive introgression [38], formation of stable hybrid zones [39], admixture, formation of hybrid swarms [40] or hybrid speciation [35].…”

Genetic Variation May Have Promoted the Successful Colonization of the Invasive Gall Midge, Obolodiplosis robiniae, in China

“…Multiple introductions are considered to produce invasive populations that are much more genetically diverse than a single source population (Sakai et al, 2001). As such, the successful establishment and invasion of many invasive species have been attributed to multiple introductions (Meixner et al, 2002;Kolbe et al, 2004;Cheng et al, 2008;Zalewski et al, 2010;Michaelides et al, 2018). For O. robiniae, in light of the short history in China, its high genetic diversity and colonization success might be also related to multiple independent invasive events.…”