The Himalayan range is rich in species diversity because

The Himalayan Range is very rich in species diversity.
Which one among the following is the most appropriate reason for this phenomenon?
  1. It has high rainfall that supports luxuriant vegetative growth
  2. It is a confluence of different bio-geographical zones
  3. Exotic and invasive species have not been introduced in this region
  4. It has less human interference
Answer: It is a confluence of different bio-geographical zones.

The Himalayan Range is Very Rich in Species Diversity:

The flora and fauna of the Himalayas vary with climate, rainfall, altitude, and soils. The climate ranges from tropical at the base of the mountains to permanent ice and snow at the highest elevations. The amount of yearly rainfall increases from west to east along the southern front of the range. This diversity of altitude, rainfall and soil conditions combined with the very high snow line supports a variety of distinct plant and animal communities. The extremes of high altitude (low atmospheric pressure) combined with extreme cold favour extremophile organisms.

The unique floral and faunal wealth of the Himalayas is undergoing structural and compositional changes due to climate change. The increase in temperature is shifting various species to higher elevations. The oak forest is being invaded by pine forests in the Garhwal Himalayan region. There are reports of early flowering and fruiting in some tree species, especially rhododendron, apple and box myrtle. The highest known tree species in the Himalayas is Juniperus Tibetica located at 4,900 metres (16,080 ft) in Southeastern Tibet.