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
Species climate requirements are useful for predicting their geographic distribution. It is often assumed that the niche requirements for invasive plants are conserved during invasion, especially when the invaded regions share similar climate conditions. California and central Chile have a remarkable degree of convergence in their vegetation structure, and a similar Mediterranean climate. Such similarities make these geographic areas an interesting natural experiment for testing climatic niche dynamics and the equilibrium of invasive species in a new environment. We tested to see if the climatic niche of Eschscholzia californica is conserved in the invaded range (central Chile), and we assessed whether the invasion process has reached a biogeographical equilibrium, i.e., occupy all the suitable geographic locations that have suitable conditions under native niche requirements. We compared the climatic niche in the native and invaded ranges as well as the projected potential geographic distribution in the invaded range. In order to compare climatic niches, we conducted a Principal Component Analysis (PCA) and Species Distribution Models (SDMs), to estimate E. californica's potential geographic distribution. We also used SDMs to predict altitudinal distribution limits in central Chile. Our results indicated that the climatic niche occupied by E. californica in the invaded range is firmly conserved, occupying a subset of the native climatic niche but leaving a substantial fraction of it unfilled. Comparisons of projected SDMs for central Chile indicate a similarity, yet the projection from native range predicted a larger geographic distribution in central Chile compared to the prediction of the model constructed for central Chile. The projected niche occupancy profile from California predicted a higher mean elevation than that projected from central Chile. We concluded that the invasion process of E. californica in central Chile is consistent with climatic niche conservatism but there is potential for further expansion in Chile.
Assuntos
Eschscholzia , Espécies Introduzidas , Altitude , Chile , Clima , Conservação dos Recursos Naturais , Modelos Biológicos , Dispersão VegetalRESUMO
PREMISE OF THE STUDY: We isolated and characterized microsatellite markers for the California poppy, Eschscholzia californica, which is an invasive species in central Chile. METHODS AND RESULTS: A total of eight polymorphic and six monomorphic loci were developed for the species. Between one and 12 alleles were observed per locus. Polymorphic loci showed heterozygosity ranging from 0 to 0.875 in a sample of 96 individuals obtained from four populations. Only one locus showed significant departures from Hardy-Weinberg equilibrium at all sites. CONCLUSIONS: The successful microsatellite amplification makes this set of primers an important tool for understanding the recent and future patterns of invasion and adaptation of E. californica into the new Chilean geographic area. The variation detected is currently being used in a more inclusive study that assesses population expansion in central Chile.
Assuntos
Eschscholzia/genética , Espécies Introduzidas , Repetições de Microssatélites/genética , Chile , Primers do DNA/metabolismo , Loci Gênicos/genética , Genética Populacional , Dados de Sequência MolecularRESUMO
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.