An ongoing study of the Kerala Forest Research Institute (KFRI) reveals that more plants have started to show its invasive nature in the forest areas of the Nilgiri Biosphere Reserve, including Wayanad Wildlife Sanctuary (WWS), a major habitat of Asiatic elephants and tigers in the country.
22 species identified
“The KFRI has already identified as many as 22 invasive plants in the sanctuary that have been posing a serious threat to its flora and fauna but, recently we have found that three more species including Lemon basil or Tea bush (Ocimum gratissimum); Red-flower rag leaf (Crassocephalum crepidioides) and Blue snake weed or cayenne snakeweed (Stachytarpheta cayennensis) have started showing invasive nature,” T.K. Hrideek, Scientist, Genetics and Tree Breeding, Kerala Forest Research Institute said.
Reproductive capacity
Invasive species generally have a high sexual reproductive capacity, ability to reproduce asexually, rapid growth from seed to sexual maturity, a great dispersal and colonization efficiency, a high tolerance to environmental heterogeneity and disturbances, a high adaptation to environmental stress (phenotypic plasticity) and a greater competitive capacity than native species, Dr.Hrideek who is leading the study said.
The Lemon basil is an aromatic perennial herb belonging to Lamiaceae family. It is native to Africa and Madagascar. It grows along with another invasive alien species like Siam weed (Chromolaena odorata) in Muthanga and Tholpetty forest ranges of the Sanctuary, says Suby, a research scholar of the team .
Red- flower rag leaf, a succulent herb belonging to family Asteraceae, is classified as one of the most aggressive weeds occurring in tropical and subtropical regions, Ms. Suby said.
Pioneer species
It is a pioneer species with the capability to produce large amounts of hairy wind dispersed seeds with silky hairs and are therefore easily blown by wind soon after detachment from mature inflorescence.
It is native to tropical Africa. Once established, its seedlings grow fast and have the potential to form dense thickets displacing native vegetation, she added.
“Cayenne snake weed is a perennial evergreen herb belongs to the family Verbenaceae.
It is native to South and central America and Caribbean. Snakeweed is introduced as garden plants from where they have spread and become a serious weed,” K .Muraleekrishnan, a research scholar, KFRI said.
Environmental tolerance
It has a wide environmental tolerance and often invades disturbed area where it can out compete with native flora. It grows on all types of soils, including infertile and dry soils, he added.
However, the spread of the plants can be managed by uprooting the plants before flowering and seed setting.
