Temperature modulates sexual reproduction in a globally invasive plant species via self‐fertilisation

Sexual reproduction is critical for the success of plant invasion, but is constrained in novel environments by mate availability and temperature. Self‐fertilisation is hypothesised to overcome this reproductive barrier, serving as a key mechanism for population establishment and geographical spread. However, it remains unclear whether alien plants have the potential to evolve increased self‐compatibility during invasion, and empirical evidence on the drivers of geographical variation in selfing capacity remains limited.

The rapid expansion of Spartina alterniflora across a wide latitudinal gradient in China (20°–40° N) offers an ideal system to study self‐fertilisation. Here, we conducted four field surveys over a 10‐year period and 2‐year pollination experiments in low‐ and high‐latitude greenhouse common gardens to determine whether there were evolutionary shifts in self‐incompatibility and to identify the latitudinal cline of self‐fertilisation. Furthermore, we transferred a subset of plants from the low‐latitude greenhouse to a controlled chamber to assess the effect of temperature on sexual reproduction.

We found that seed set increased consistently with latitude over a 10‐year period. In particular, a positive relationship between latitude and seed set under the control and self‐pollination treatments was observed only in the high‐latitude common garden, providing evidence for enhanced selfing capacity of high‐latitude populations. Moreover, the chilling treatment improved the seed set under the control and self‐pollination treatments. We also found that the optimal temperature for seed set during pollen shedding was 22–25°C in the greenhouse common gardens.

Synthesis . These findings offer new insights into geographical variation in self‐fertilisation and highlight that temperature is a key driver modulating sexual reproduction and facilitating invasion through enhanced self‐compatibility evolution in invasive plant species.