What disadvantages do seedless vascular plants have over other extant species of vascular plants?
gardengallivant, she’s referring to seedless vascular plant species in comparison to seed plants, i believe, not the special case of seedless hybrids or varieties. The major disadvantage of seedless vascular plants (e.g., psilophytes, lycophytes, and sphenophytes) is that, unlike seed plants (e.g., gymnosperms, angiosperms), their gametes are not typically dispersed by biotic vectors. That is, many seed plants have their seeds dispersed by insects, birds and mammals, which often increases the probability that a seed will be able to establish itself in a new area (and not find itself competing with its parent for light, water, etc.). Also, being dispersed by an animal often means that the seed is often provided with a bit of fertilizer (feces) from the disperser, especially if the seed was originally in a fleshy fruit. Sporangia dispersed by wind, for example, will rarely get that advantage.
