Q.According to a recent wildlife report, the biggest threat to the tiger's survival in Mudumalai Tiger Reserve (MTR) was found to be a small, beautiful flower, Lantana camara, a tropical American shrub, that invaded 40% of India's tiger range. Tamil Nadu department's Lantana weed eradication drive helped to restore the dying MTR thereby also reducing human-wildlife conflicts. MTR is home to 25 species of grasses and legumes. Answer the given questions based on the information given above.

Concept: Invasive species and ecosystem balance

Lantana camara is an invasive alien species that disrupts native ecosystems by outcompeting indigenous flora, altering habitat structure, and cascading through trophic levels.

1. How removal of Lantana helped restore MTR: Lantana forms dense thickets that smother native grasses and legumes—the primary food base for herbivores like deer and gaur. When Lantana was removed, native vegetation (25 species of grasses and legumes) regenerated, restoring grazing grounds. This increased herbivore populations, which in turn provided adequate prey for tigers. The improved habitat quality also reduced herbivore movement into human settlements, thereby lowering human-wildlife conflicts. Essentially, eradication restored the grassland-herbivore-carnivore food chain.
2. Why Lantana invasion is a concern: …

Understanding invasive species and ecosystem disruption

An invasive species is a non-native organism introduced into an ecosystem where it has no natural predators or competitors. Lantana camara, native to tropical America, behaves aggressively in Indian forests because the ecological checks that limit its growth in its native range are absent here. It spreads rapidly, forms dense thickets, and monopolizes resources like sunlight, water, and nutrients.

The key to understanding this problem lies in recognizing that ecosystems function as interconnected webs. A tiger reserve isn't just about tigers—it depends on a complete food chain: grasses and legumes support herbivores (deer, gaur, wild boar), which in turn support apex predators like tigers. When an invasive plant disrupts the base of this pyramid, the entire structure collapses.

(a) How removal of Lantana helped restore MTR

The restoration works through a cascade of ecological recovery:

1. Native vegetation rebounds

   When Lantana is removed, the 25 species of native grasses and legumes that evolved in MTR can reclaim their space. These plants are adapted to local soil, climate, and wildlife, forming the natural ground cover of the forest.

2. Herbivore food supply increases

   Native grasses and legumes are palatable and nutritious for herbivores like chital (spotted deer), sambar, and gaur. Lantana, by contrast, is toxic to most herbivores and inedible. With native plants restored, herbivore populations can grow and sustain themselves.

3. Prey base for tigers recovers

   Tigers are obligate carnivores that hunt medium to large herbivores. A healthy herbivore population means adequate prey density. More prey means tigers can hunt successfully within the reserve boundaries instead of wandering into human settlements.

4. Reduction in human-wildlife conflict

   When prey is scarce inside the reserve, tigers venture into villages and agricultural lands, leading to livestock predation and dangerous encounters. Restoring the prey base keeps tigers within their natural habitat, reducing such conflicts.

5. Overall ecosystem health improves

   Native plants support not just herbivores but also insects, birds, and smaller mammals. The entire biodiversity of MTR benefits, creating a resilient, self-sustaining ecosystem.

(b) Why Lantana camara invasion is a cause of concern

The invasion threatens MTR at multiple ecological levels:

1. Competitive exclusion of native flora

   Lantana grows faster and denser than native species, shading them out and depleting soil nutrients. The 25 native grass and legume species cannot compete, leading to local extinctions and loss of plant diversity.

2. Collapse of the herbivore population

   With native forage replaced by inedible Lantana, herbivores face starvation or are forced to migrate. A 40% invasion across India's tiger range represents a massive loss of grazing habitat.

3. Disruption of the predator-prey balance …