Local adaptation, increased colonization ability, and resistance to natural enemies: The invasion of the California poppy (Eschscholzia californica) in Chile

Do invasive plants evolve in their new range? I have addressed this question with the California poppy, (Eschscholzia californica Chain.), native to the west coast of North America and invasive in Chile. Seeds were collected from native and invasive plants and grown in common gardens in California. Experiments were designed to answer the following questions: (1) are there genetic differences in size and fecundity between native and invasive poppies, and are these differences consistent across variable growing environments? (2) are there differences in herbivore resistance between native and invasive poppies? and (3) do native and invasive poppies show similar adaptations to the environments where they were collected?; Invasive poppies from Chile were found to grow larger and be more fecund than native poppies, but only when grown with reduced competition. This suggests that invasive poppies have evolved to take advantage of disturbed conditions. Secondly, two native herbivores performed better when fed on a diet of flowers from native populations. This result is contrary to the expectation that invasive plants may attain larger size by decreasing the amount of resources allocated to traits that provide resistance to herbivores. Finally, traits of both native and invasive poppies were correlated with their source environment. Plants collected from coastal areas in both Chile and California tended to be shorter, smaller plants with smaller seeds and flowers, and they germinated and flowered later than plants collected from inland locations. Size and fecundity traits in both native and invasive poppies were correlated with the latitude and average rainfall of the location where they were collected: the plants that grew the largest and were the most fecund in the common gardens were collected in drier areas closest to the equator in both California and Chile. This research demonstrates that invasive California poppies have diverged from native populations in the brief time since introduction, evolving an increased colonization ability and increased resistance to herbivores, but also possess local adaptations that parallel those found in Californian populations.