A groundbreaking study from the Indian Institute of Science (IISc) reveals that a plant's ability to self-fertilise is a crucial factor driving its invasiveness, significantly impacting local ecosystems and biodiversity.
Key Points
- IISc study identifies self-fertilisation as a key trait for plant invasiveness.
- Invasive plants can reproduce uniparentally, establishing new populations without cross-pollination.
- The study compared 28 plant species, including invasive, non-invasive alien, and native types.
- Aggressive invaders like Ageratum conyzoides and Bidens pilosa evolved uniparental reproduction in India.
- Reproductive strategy should be a core component of future weed-risk assessment programmes.
A plant's ability to reproduce on its own -- through self-fertilisation -- could be a key trait that helps it become invasive, according to a recent study from the Indian Institute of Science (IISc), Bengaluru.
Invasive plant species are non-native organisms that spread aggressively, displacing local flora, altering local ecosystems and reducing biodiversity.
While most flowering plants need pollen from another individual of the same species to produce seeds, plants of some species can reproduce using their own pollen, or even without pollen -- this way even a single plant can establish a new population.
Understanding Uniparental Reproduction And Baker's Law
The idea, known as Baker's law, suggests that plants capable of 'uniparental reproduction' or self-fertilisation should be better invaders, researchers said.
Saskya van Nouhuys, associate professor at the Centre for Ecological Sciences (CES), IISc, and Narashiman Nagendra Rao, a former MSc student at CES, examined 28 species from the daisy family (Asteraceae), comparing 11 invasive species, eight non-invasive alien species, and nine native species.
The study, published in the journal Biological Invasions, involved collecting plants from disturbed habitats such as roadside and open spaces across Karnataka and Tamil Nadu over a year.
Seeds or plant cuttings from at least five individuals of each species were grown on campus, while a few hard-to-grow native species were studied in the wild, with a total of about 900 plants examined.
Key Findings On Invasive Plant Traits
The researchers tested whether the plants could reproduce without cross-pollination by comparing self-pollinated and naturally pollinated flowers, and then assessed seed viability and germination.
They found that all the 11 invasive Asteraceae species studied could reproduce uniparentally, while most native and non-invasive alien species remained self-incompatible -- they usually required a pollen from another plant.
"Uniparental reproduction is a conceptually simple trait. It has been exciting to see such clear evidence of its advantage for invasive species," van Nouhuys said.
Evolutionary Shifts In Reproductive Strategies
Two especially aggressive invaders, Ageratum conyzoides and Bidens pilosa, were found to be largely self-incompatible in their native range of Mexico.
However, in India -- where the species are alien -- they had evolved to become uniparental, suggesting that individuals capable of self-fertilisation were favoured during the invasion process.
"Before our experiments, the idea of reproductive strategies shifting during invasion seemed like a very far-fetched idea to me and I thought that previous evidences of such shifts were very rare occurrences," Rao said.
"The results from our experiments and that of our collaborators absolutely baffled me," Rao said.
Implications For Weed-Risk Assessment
As invasive species continue to spread worldwide, reproductive strategy should become a routine part of weed-risk assessment programmes, which researchers suggest are used to predict which introduced plants are most likely to become future invaders.
"Invasive species are called invasive for a reason. They establish and then flourish in a new location. When this happens, existing species decline or disappear entirely, which changes the whole landscape," van Nouhuys said.
