Patterns of flowering phenology can affect the success of plant invasions, especially when introduced species spread across a wide range of latitude into different climatic conditions. The distribution of intertidal plant Spartina alterniflora across a wide latitudinal gradient in its invasive (China, 19-41 °N) ranges provides a model system to evaluate the adaptive mechanism of flowering phenology in this widely distributed exotic species. The potential genetic basis in flowering phenology of S. alterniflora has been documented in our previous single common garden experiment at low latitude in a subtropical region (24 °N), however, we suspect that there would be an interactive effect of genetic basis and environment in this latitudinal pattern. Therefore, we employed common gardens at multiple latitudes (21 °N, 24 °N and 38 °N), where the high and low latitude common gardens were located in the northern and southern edge of S. alterniflora distribution range respectively, and we conducted a corresponding field survey as a test of this idea in 2019.
Results/Conclusions
The flowering time in the field showed a hump-shaped relationship with latitude, consistent with previous research. Flowering time varied among the gardens, with linearly positive relationship with latitude, which was different to the field pattern but accorded with the general bioclimatic law of phenology. Evidence of evolution was found as decreasing flowering time with increased latitude of provenances within common gardens. However, the effect differed among common gardens, with the greatest slope in the high-latitude garden and weaker effect in the southern gardens. These results indicated a distinct genetic-by-environment effect on flowering phenology with higher selection pressure at high latitudes, which completed our previous conclusion and documented the latitudinal adaptive mechanism in flowering phenology of the invasive S. alterniflora in China.