When you paleoZOOLOGISTS start speculating about plants, you always get in
trouble (e.g., Bakker). You may remember that Gingkos are gymnosperms,
thus do not have "fruits". The fleshy tissue surrounding Ginkgo seeds is
simply a fleshy integument, or seed coat, not a swollen ovary as in the
true fruits of angiosperms. [Note, though, that the Ginkgo seed does give
plant systematists much to ponder in the evolution of the Anthophyta.] As
far as its smell being an attractant for a dispersal agent, the Ginkgo
fragrance of rotting flesh would only attract those animals who are
scavengers. Are there many dinosaurs known to be scavengers?
Another possible adaptationist explanation of the high-sugar content of
fleshy seed coats and ovaries is that the decomposing sugary coat would
facilitate the growth of soil microbes, who are typically C-limited rather
than N-limited, and some of these soil microbes (particularly fungi) may be
mycorrhizal species that develop mutualistic associations with the
developing roots of vascular plants. These mutualisms increase nutrient
uptake potential for the plants.
One must remember, though, that not every feature is adaptive, and
certainly not every adaptive feature of a plant is related to an
association with animals.
Wendy Anderson, Ph.D. (Plant Ecology)
Assistant Professor of Biology
Springfield, MO 65802