Abiotic pollen and pollination: ecological, functional, and evolutionary perspectives

The transport and capture of pollen in similar to 20% of all angiosperm fam ilies occurs in air and water. In other words, pollination is abiotic and o ccurs via the fluid media, not an animal vector. Whereas some early concept s considered abiotic pollination to be largely a stochastic phenomenon, the re is sufficient evidence to indicate that wind pollination (i.e. anemophil y) and water pollination (i.e. hydrophily) have deterministic features and are sophisticated fluid dynamic solutions to the problem of pollen release, dispersal, and capture. An abiotic pollination syndrome is defined in which there is spatial or tem poral separation of carpellate and staminate flowers, which are drab, a red uction in perianth parts, stigmas and anthers are exposed to the fluid, and typically unclumped pollen may be produced in large amounts. Separate poll ination syndromes are defined for anemophilous (i.e. wind-pollinated), ephy drophilous (i.e. surface-pollinated). and hydrophilous (i.e. submarine-poll inated) plants. Distinctions are based on habitat and physical conditions f or pollination. pollen size, shape, and ultrastructure, morphology and ultr astructure of stigmas, and outcrossing rates. For example, anemophilous pol len are spherical and small. ephydrophilous pollen are spherical or renifor m and large, while hydrophilous pollen are filiform (i.e. filamentous) or f unctionally filiform. The pollination mechanisms and mechanics associated w ith these syndromes reveals a strong evolutionary relationship between plan t morphology and fluid dynamics.