Avoiding eating pollinators - myth?

[Alexis]

The general consensus seems to be that sarracenia flower after pitchering to avoid eating their pollinators, or keep their flowers away from the traps.

The latter seems to apply to purpurea and psittacina, but oreophila tends to flower after or with the first opening pitchers. Minor tends to flower late in the season, amongst the gaping pitchers and now I've just noticed this image of an alata stand:




(Barry's image, hosted on this site)


Is the idea of not eating pollinators a design feature do you think, or is it pure chance that some species flower before the majority of pitchers open, whereas others don't?

[Michael Catalani]

Apr 8, 2008 9:56:56 GMT Alexis said:

Is the idea of not eating pollinators a design feature do you think, or is it pure chance that some species flower before the majority of pitchers open, whereas others don't?

S. oreophila pitchers are open in full force before the flowers are in petal. I have theorized that the plant delays flowering because the areas that the plants grow in naturally are susceptable to late spring freezes, which could easily damage the flowers.

[DroseraBug]

I did some research into this years ago in college. In my opinion it is very much worth some field experimentation. S. flava shoots up flowers earlier than pitchers. S. minor hoods may interfere with Bombus spp. capture. However, the others mentioned above such as S. alata conflict with this hypothesis unless it somehow has to do with temporal pollinator vs prey attractant affects in pitchers vs. flowers or something. I'm glad you posted this thread. Good topic of discussion. I've discussed this topic with some very experienced carnivorous plant botanist and horticulturalists. I've thought of some ways to manipulate potted Sarras before. Someone needs to do an experiment.

[Alexis]

With regards to out in the field, is is possible to find alata stands full of flowers, but pitchers just only a few inches high?

[Dave Evans]

Well, with S. alata and S. minor the flowers are below the openings of the pitchers.

With S. purpurea and S. psittacina the flowers are high above the rosettes. But S. psittacina appears to be geared toward catching completely different prey so I don't see any connection between that species and this theory...

S. rosea flowers are held right above last season's pitchers, but they generally start to flower before the new pitchers open.

S. rubra, I don't know much about it. But I've seen that the flowers tend to open before the pitchers. Same for S. flava.

S. oreophila appears to be the one species most geared toward eating its pollinators...

S. leucophylla open their flowers before the pitchers open and the spring pitchers are shorter than the flowers.

However, I think most Sarracenia don't mind making a meal out of their pollinators and the theory about them going out of their way to avoid it doesn't hold water, but most species probably lower the chance of it happening by flower position vs. mouth position at least as much as using timing as neither possible method appears to be strictly adhered to.

I also think Droserabug could be right about the pitchers taking a few days to become fully functional.

[Alexis]

Cheers Dave.

Well, with S. alata and S. minor the flowers are below the openings of the pitchers.

Maybe so, but would the short distance make a difference? Do insects go straight for the flowers over the pitchers, in which case the efficiency of the pitchers would be compromised for a couple of weeks.

[DroseraBug]

Hymenopteran pollinators will associate a reward with a color/shape visual cue. This is why I mentioned the need for experiments. If there are small differences in the timing of pitcher vs. flower elevation this could be important in bee attraction. The bees could associate the flower color, shape, possibly elevation with a reward.

I've done experiments with honey bees. Example: take two cartoon pictures for example one with an apple and a separate one with a picture of bugs bunny and lay them on a flat surface. Next only drop some sugar water or some other sweet substance on the bugs bunny pictures. Most of the foraging bees will swarm to bugs bunny. OK, come back later and lay a new apple and bugs bunny picture down with no reward at all. The bees should have associated bugs bunny with a reward and should return to the bugs bunny picture even without the sugar.

Studying the temporal effects of flower vs. pitcher emergence and temporal attractant differences would be a good experiment. Not only is there a spatial difference in some species. If for example the pollinator receives a reward from the flowers instead of from pitchers, it should continually return to that flower shape/color for that reward and not to the pitcher. Just my opinion though.

V

[BarryRice]

I think that we make too much of the whole matter of how Sarracenia time their pitchers to avoid eating its pollinators. Sarracenia pitchers have an extremely low capture efficiency--think of all those times you've watched a fly, bee, wasp, or ant crawl around the pitcher opening but, despite the suspense, escape completely free. The capture rate is almost negligible.

I agree with Dave Evans, that S. oreophila is the species that seems most geared towards eating its pollinators. For example, see below. Sarracenia oreophila produces its flowers after the pitchers are mature, and has no problem with the green flowers being right at the same height and placement of the green pitcher openings.

At one point, I toyed with the notion that this apparent dysfunction might explain the small and spotty range of S. oreophila but a few trips to see them in the wild revealed the fruit are all filled with seed. Clearly this plant does not have a problem getting pollinated.

[Michael Catalani]

I've watched bumble bees pollinate my own Sarracenia. They will go from flower to flower, working all of them over. They seem oblivious to the hundreds of open pitchers among the flowers.

In the wild, it is not unusual for S. leucophylla pitchers that were produced in late fall to remain viable through the next spring. Theres always an enormous number of awaiting S. leucophylla pitchers in the spring when the plants are in flower.