Question

One hypothesis for the high biodiversity of flowering plants is their coevolution with animals.  Why might coevolutionary relationships between plants and animals lead to diversification in plant (and insect) groups?

Answer 1

One special feature of angiosperms is that they produce flowers. Flowers help in cross pollination by attracting different insects and birds as pollinators. There happens a co evolution between a flower and the type of pollinator the flower or plant prefers. This evolutionary pressure drives further diversity in the angiosperic plants.

The reasons for coevolution between plant and animals leading to high biodiversity are following-

Each class of plants and pollinator target each other on several parameters like development of floral architecture for making suitable landing space for polliinators.

Production of nectar for the target pollinator- The flowers evolving for ornithophily develop-

Bright red colour for visibiity from long distances

Produce huge amount of nectar because of high energy need of birds than in comparison to insects

Accessibility of floral nectar by only that pollinator which can help in pollination- The flowers evolve differently to save it's nectar onlu for its pollinator like

Flowers evolved for ornithophily developed tube shaped corolla while birds evolved thin and longer beak

Some flowers lika Mimulus evolved nectar guides which are visible only to bees (UV light vision) and not to other animals.

So, this continuous striving of plant to protect it's nectar for only the pollinator for maximizing chances of better pollination is the reason for high coevolutionary diversity.