Long‐distance dispersal has been important in explaining the present distributions of many plant species. Despite being infrequent, such dispersal events have considerable evolutionary consequences, because bottlenecks during colonization can result in reduced genetic diversity. We examined the phylogeographic history ofLycium carolinianum, a widespread taxon that ranges from southeastern North America to several Pacific islands, with intraspecific diversity in sexual and mating systems.
We used Bayesian, likelihood, and coalescent approaches with nuclear and plastid sequence data and genome‐wide single nucleotide polymorphisms to reconstruct the dispersal history of this species. We also compared patterns of genetic variation in mainland and island populations using single nucleotide polymorphisms and allelic diversity at theS‐RNasemating system gene.
Lycium carolinianumis monophyletic and dispersed once from the North American mainland, colonizing the Pacific islands ca. 40,100 years ago. This dispersal was accompanied by a loss of genetic diversity in SNPs and theS‐RNaselocus due to a colonization bottleneck and the loss of self‐incompatibility. Additionally, we documented at least two independent transitions to gynodioecy: once following the colonization of the Hawaiian Islands and loss of self‐incompatibility, and a second time associated with polyploidy in the Yucatán region of Mexico.
Long‐distance dispersal via fleshy, bird dispersed fruits best explains the unusually widespread distribution ofL. carolinianum. The collapse of diversity at theS‐RNaselocus in island populations suggests that self‐fertilization may have facilitated the subsequent colonization of Pacific islands following a single dispersal from mainland North America.