RESUMO
The component Allee effect has been defined as 'a positive relationship between any measure of individual fitness and the number or density of conspecifics'. Larger plant populations or large patches have shown a higher pollinator visitation rate, which may give rise to an Allee effect in reproduction of the plants. We experimentally tested the effect of number of conspecifics on reproduction and pollinator visitation in Eschscholzia californica Cham., an invasive plant in Chile. We then built patches with two, eight and 16 flowering individuals of E. californica (11 replicates per treatment) in an area characterised by dominance of the study species. We found that E. californica exhibits a component Allee effect, as the number of individuals of this species has a positive effect on individual seed set. However, individual fruit production was not affected by the number of plants examined. Pollinator visitation rate was also independent of the number of plants, so this factor would not explain the Allee effect. This rate was positively correlated with the total number of flowers in the patches. We also found that the number of plants did not affect the seed mass or proportion of germinated seeds in the patches. Higher pollen availability in patches with 16 plants and pollination by wind could explain the Allee effect. The component Allee effect identified could lead to a weak demographic Allee effect that might reduce the rate of spread of E. californica. Knowledge of this would be useful for management of this invasive plant in Chile.
Assuntos
Comportamento Animal , Eschscholzia/fisiologia , Flores , Aptidão Genética , Polinização , Sementes/crescimento & desenvolvimento , Animais , Ecossistema , Eschscholzia/crescimento & desenvolvimento , Frutas , Insetos , Espécies Introduzidas , Pólen , Reprodução , Especificidade da Espécie , VentoRESUMO
Insight into the speed and predictability of local adaptation can be gained by studying organisms, such as invasive species, that have recently expanded their geographical ranges. Common garden studies were designed to address these issues with the California poppy, Eschscholzia californica, collected from a wide range of environments in both its native (California) and invasive (Chile) ranges. We found similar patterns of plant trait variation along similar abiotic gradients in plants collected from both areas. Multivariate analysis demonstrated that coastal plants from both areas tended to be shorter, smaller plants with smaller seeds and flowers that germinate and flower later than plants collected from inland locations. In addition, size and fecundity traits in both native and invasive poppies were correlated with average rainfall totals; the plants that grew the largest and were the most fecund during the first year of growth originated from the driest areas. This parallel variation suggests that these traits are adaptive and that these patterns have evolved in Chile during the 110-150 years since introduction.