Background: Under the background of rapid economic globalization and increasing global climate change, biological invasions have become one of the three major environmental problems in the world and thus represent an important component of global change. The biogeochemical cycle of ecosystems under the influence of global change and human activities has facilitated the long-distance spread of invasive plants and animals, thereby accelerating the invasion rate of alien species. Spartina alterniflora, a global invasive plant in coastal wetlands, has imposed a serious threat to native ecosystems of coastal wetlands in different geographical regions. In recent years, studies on the ecological adaptability of S. alterniflora across latitudinal gradients have attracted extensive attention. Different life history traits of S. alterniflora have emerged latitudinal patterns in both invasive and native ranges.
Progress: The invasion mechanisms of alien species are complex and variable, and the existing studies on the invasion mechanisms of S. alterniflora mostly focused on only one aspect. The successful invasion of S. alterniflora across latitudinal gradients is the combined result of the interaction of multiple invasion mechanisms at various stages of life history. Through the integration of different traits, life history responses, and genetic structure of S. alterniflora along the latitudinal gradients, this review improves our understanding of the ecological adaptation of the invasive S. alterniflora to the latitudinal gradients during its life history. The successful invasion of S. alterniflora along the latitudinal gradients was achieved mainly through local adaptation, phenotypic plasticity, natural selection, rapid adaptive evolution, intraspecific hybridization, and genetic variation. Since S. alterniflora was introduced into China more than 40 years ago, its individual growth and developmental traits and life history responses have gradually formed significant latitudinal patterns and produced a series of ecological adaptive mechanisms to the latitudinal gradients. The role of phenotypic plasticity is greater than that of genetic differentiation in the ecological adaptation of vegetative growth to latitudinal gradients in invasive area. In addition, phenotypic plasticity and genetic differentiation both affect the ecological adaptation of reproductive traits (seed germination, seed set, and flowering phenology). Thus, reproductive traits are more likely to undergo rapid adaptive evolution than vegetative growth in S. alterniflora in China, where it was invaded. However, the evolutionary trends of these traits are contrasting between invasive and native populations.
Perspective: Based on the temporal scale of the invasion and dispersal history of the global coastal wetland invasive plant S. alterniflora in China for more than 40 years and the spatial scale of its wide latitudinal distribution, this paper reviews the geographic variation patterns of different biological traits of S. alterniflora. There is a lack of studies on the correlation between different traits of S. alterniflora, including the trade-offs among traits and the overall life history process, which will be important for a systematic understanding of the evolutionary response and invasion dynamics of S. alterniflora. Additionally, this paper systematically describes the genetic structure and variation of S. alterniflora at microscopic scale. However, there is still a lack of research combining macroscopic and microscopic scales. Subsequent work combining macroscopic and microscopic studies will help to clarify the influence of genetic structure on the life history adaptations of S. alterniflora, which will deepen our understanding of the invasiveness of S. alterniflora. S. alterniflora not only shows excellent ecological adaptability at a wide geographic scale, but also exhibits extremely strong invasive ability at small spatial scales such as tide levels and watersheds. However, at these scales, there are still a lot of research gaps in the study of the response and adaptation of S. alterniflora to environmental gradients at various life history stages. The combination of various methods from different spatial scales will be a key direction for future research on S. alterniflora, in order to further reveal the invasion process and mechanism of S. alterniflora invasion.
