Biotic pollination refers to the (mostly) mutually beneficial (mutualistic) interactions between some flowering plants and pollinators (insects, birds, bats, etc.). Pollinators carry or move pollen grains from the anther to the receptive part of the pistil within or between flowers. In return, pollinators typically receive a reward, such as nectar or protein-rich pollen, from the flower.
Pollination interactions range from highly specialized to widely generalized. Highly specialized pollination relationships include instances when only one animal species pollinates only one flowering plant species, which in turn is only pollinated by that animal (e.g. the yucca and the yucca moth). Generalized pollination systems occur when multiple animals pollinate a given species of plant or when a certain pollinator visits many different species of plants.
Some plants are self-pollinated, meaning that pollen is transferred within the same flower or among flowers on a single plant. But most plants are cross-pollinated, meaning that the pollen must be transferred from anthers on one plant to the stigmas of another individual. Such cross-pollination increases genetic variation in plants. Genetic variation may help plants evolve resistance to herbivores and pathogens.
When there is an strong interdependence between two species (a specialized interaction), those species may evolve together over time, exerting evolutionary pressure on each other. The coevolution between plants and their animals pollinators has long been considered to be a primary driver for the evolution of the tremendous variety of flowering plants on earth. However, through long-term field ecology projects, many scientists at RMBL have documented that both plants and pollinators in this ecosystem and others are characterized by generalized pollination interactions while well-documented instances of highly specialized interactions are relatively rare.
Pollination is clearly important to both flowering plants and their pollinators, but it is also important to any species that eats the fruits of flowering plants. Many economically important agricultural crops require biotic pollination. The list includes common fruits such as apples, blueberries, melons, and many others. It also includes crops we don’t often think of as fruits, like almonds, squash, tomatoes, and coffee beans or plants that humans don’t eat, like alfalfa or other grasses and grains used as feed.
But pollination is important for more than just agriculture - flowering plants are a critical component of many terrestrial ecosystems. Over 100,000 different invertebrates (butterflies, moths, bees, flies, beetles, etc.) and more than 1000 different vertebrates (birds, mammals, reptiles, etc.) pollinate roughly 75% of flowering plants, making the interactions between plants and pollinators a dominant mode of species interactions in terrestrial ecosystems.
anther - pollen producing male organ of a flower
mutualism - interaction between individuals of different species that benefit both partners
pistil - female organ of a flower