Pollination is the transfer of pollen grains that leads to the germination of the pollen grain on a stigma and fertilization of a plant ovule resulting in seed/fruit set. Pollen grains can be transferred from the anther to the stigma of the same flower or they can be transferred to another flower of the same or another plant.

Pollen movement results in genetic exchange and the recombination of genes. Self-pollination (the transefer of pollen between anthers and stigmas of the same plant) can lower genetic diversity. To compensate, flowering plants use several modes of pollen transfer to cross-pollinate:

• Wind pollination (anemophily)
• Water pollination (hydrophily)
• Animal pollination (zoophily)
  

Pollination by insects (entomophily) occurs in ~67% of flowering plants throughout the world. In temperate environments, such as Montana, plants and insects are typically opportunistic with regards to one another because of the yearly and seasonal variations in diversity and abundance, therefore, neither plants nor insects usually depend on one species for their pollination or resource needs.

As altitude or latitude increases, greater proportions of plants are pollinated by opportunistic pollinators. Research has shown that the most important pollinators in the high arctic of the Northwestern Territories of Canada were Diptera, specifically the families Empididae and Syrphidae. Many of the flowers in these areas were pollinated primarily by flies where as others were pollinated by bumble bees. Similarly, another study near Springville, UT at elevations of 1495 m and 3170 m found that relative species richness of Hymenoptera decreased with increasing elevation, but dipterans richness increased. Beetle and butterfly richness was low, relative to bees and flies, at both sites but also decreased with elevation.

References