Fruits of Vaccinium myrtillus species are berries, that is flashy fleshy fruits. They are appealing, and not only to humans. Indeed, they’ve been selected to be attractive. That’s the way this plant generally disperses seeds, just like many other plants betting on animals to go away.
To natural dispersers of bilberries, the post ingestion trip is a nice digestive walk (or flight, if you’re a bird). To the berries, the travel is also a digestive walk through, though I suspect less enjoyable. We tend to find it disgusting, but that’s because we are dys-guts-ive. The berry doesn’t really care of course. But what about seeds?
Well, seeds probably enjoy getting through digestive tract, at least of birds. The gut trip through the gut and tripes actually increase their germination rates, compared to seeds who don’t* (well the main point of the study is more to highlight variation within and between years, with a neat decline in germination during the season). This is not so surprising, for we would expect fleshy fruits whose fates are tied to consumption by animals to have somewhat evolved adaptations to this kind of dispersal. But I was wondering to what extant such adaptations would exist. Would it be species specific (i.e. varying across different species of dispersers)? And would it be a function of specific frugivore abundance? I mean, an ideal adaptation™ would be to see the best increase in germination occuring with digestion by the most frequently encountered berry-eater. But would we see otherwise that it would be exciting.
Well, the problem is that we don’t really have the data yet. Different species of Vaccinium with different species of birds between studies, and different germination conditions don’t make the comparison reasonable. Moreover, this also varies seasonally and between years so… Who will have the guts for such experiment? Wait! There’s something if we want to extend the comparison a bit. There’s an animal who seems not to change germination rates of bilberries after ingestion. Bear with me. A bear**.
* Honkavaara, J., Siitari, H., Saloranta, V. & J. Viitala. 2007. Avian seed ingestion changes germination patterns of bilberry, Vaccinium myrtillus. Annales Botanici Fennici 44: 8–17.
**Well, this is discussed in the present study so I don’t have the details. But I wonder what the Material & Methods section of the “bear study” would be…