Pollinators and Robbers (and Squirrels)

The last tulips in my garden this morning…

It is finally flower season! How I love it! However the happiness of the season is constrained somewhat by the gray squirrels, which have systematically beheaded my tulips (despite the fact that I have been simultaneously trying to ward the pests away with foul chemical sprays and appease them with nuts).  Alas, most of my tulips now lie sad and beheaded beneath the cherry blossoms.

My (ineffective) struggles to protect my beloved tulips remind me of the struggles of wild flowers which face a similar arms race.  The tulips I plant are propagated by big nurseries, and the squirrels don’t really want to eat the blossoms: they merely tear them apart to see if there is any food inside (and (probably) because the miserable rodents enjoy my suffering).   Flowers are plant reproductive organs which exist to repopulate the species.  In the case of garden tulips this involves a complicated relationship between myself, Lowes, tulip farms, nurserymen, and squirrels.  In the world of wildflowers, the players are fewer and the stakes are much higher.

Buff-tailed Sicklebill (Eutoxeres condamini) by Ernst Haeckel

Flowers and their pollinators have a mutualistic relationship:  the hummingbird –or bee, or moth, or bat, or whatever–gets a meal while the flower directly shares its gametes (in the form of pollen stuck to the beak or fur) with distant members of the same plant species.  Some blossoms coevolve to provide nectar to specialized pollinators as with the famous sicklebill hummingbird (which feeds on the nectar of specialized Centropogon and Heliconia flowers which fit the bird’s beak and produce colors appealing to the hummingbirds).

This whole relationship falls apart sometimes though, thanks to a behavior first reported by Charles Darwin. Some animals are nectar robbers.  Lacking the long proboscis or curved beak or special senses necessary to obtain the sweet nectar which the plant offers as a reward for its reproductive interlocutors, some animals simply cut through the blossoms or rip them apart to take the pollen.  Although this can be beneficial (if a robber ends up pollinating a flower anyway, or forces a legitimate pollinating species to travel over a larger area—and thus provide greater genetic diversity), more often it is destructive.

Um, sure I guess…thanks, art department.

Interestingly, a recent study determined that bumble bees learn how to cut holes in flowers and steal the nectar directly from other bumble bees (you can read about the particulars of the study here).  Bumble bees are not the only pollen robbers–various lepidopterans, bats, and birds are guilty in various ways–but the bumble bee example is the first case to prove Darwin’s thesis that such robbing behavior was learned by insects.

It all begins to make more sense now…

Flowers, though passive, are not helpless.  Over generations, they coevolve with both the robbers and the pollinators—which is how they obtain so many convoluted and fanciful forms (and why there are so many toxicologically and pharmacologically active compounds therein).  It is worth thinking about when you encounter a spring landscape of beautiful flowers—beneath the surface lies a world of sex, appetite, and larceny.

The horror!

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