Invasive plants’ success may start with invasive pollen

How plants cope with pollen from other species, heterospecific pollen (HP), may explain some of the success of invasive plants, according to a paper recently published in the American Journal of Botany. “Our results showed that, in the field, HP receipt negatively affected the pollination success of native species but not of the invasive species,” said Alexander Suárez‐Mariño and colleagues in their article. “Our results also showed that the invasive Bidens pilosa received four times more HP than natives. These results combined, suggest that the invasive B.pilosa may be tolerant to the negative effects of HP transfer, which could contribute to its invasion success in the studied area.”

The study is the first to look at the effect of native pollen on invasive plants. The authors say that so far, all pollen studies have examined the impact of invasive pollen on native species.

The scientists went to the Yucatan Peninsula of Mexico to examine how pollen interacts between native and invasive species. The invasive species the studied was Bidens pilosa, an invasive species found around the world. The native plants were Cakile edentula and Scaevola plumieri

C. edentula, American searocket, is a wind, insect and self pollinated plant typically found in coastal areas. While it is invasive in Asia and Australia, it is native in Mexico. S. plumieri is another plant with a mixed mating system, which is found in Africa, but is also native to Mexico.

The team examined pollen deposition in the field. They also used hand-pollination experiments. By doing this, they could observe how the time of arrival of heterospecific pollen affected pollen tube success.

“Interestingly, the invasive species not only received approximately four times more HP than the natives but also received almost double the number of HP donor species…,” say Suárez‐Mariño and colleagues in their article. “Although the HP reception on invasive species has been scarcely studied, this result is not entirely surprising. Invasive plants typically have a generalized pollination system, and they usually share a high level of pollinators with native plants.”

However, when it came to interference, the HP load size had an adverse effect on the native plants, but not the invasive plant. “This result suggests a differential “tolerance” to HP between the invasive and both native species,” say the authors.

It’s this differential that most interests the authors. It opens yet another area where invasive and native plants may compete. Yet while the experiments were interesting for B. pilosa, Suárez‐Mariño and colleagues say that similar hand-pollination analyses for other species in other contexts need to be done. “Such experiments will allow us to fully understand the role of HP transfer interactions in mediating invasive species success in novel communities.”