Millions of species inhabit Earth, and because all these different species often live in the same spaces, they must share or compete for the same resources. In the world of flowers, a vital resource is the insect pollinator. With an estimated 250,000 to 400,000 flowering species, the competition to attract an insect pollinator is fierce. Similar to how some humans will go to great lengths to get the attention of the opposite sex, so do flowers when it comes to courting the insects necessary to keep the flower family going. Generally speaking, flowers employ the characteristics of showy petals and sepals, offers of food in the form of nectar or pollen, nectar guides, appealing scents and the gamut of colors to attract insect pollinators. Evolution, however, has changed the game for some flower species, creating floral outliers that do things just a bit differently. When it comes to “luring” the popular pollinators, these floral outliers do so by means of deception. Seeing as flowers can’t don a wig, put on stylish clothes or get plastic surgery, how then do these sneaky species deceive?
Before heading down that road, let’s back up for a moment and have a refresher course in flower biology and anatomy.(No eye-rolls, please.) In plant taxonomy, flowering plants are known as angiosperms or magnoliophyta. They are vascular seed plants in which the ovule (egg) is fertilized and develops into a seed in a hollow ovary usually enclosed in a flower whose function is to ensure fertilization of the ovule. A flower may contain both male and female reproductive orgas, or it may have only one or the other. The male reproductive organs are called stamens, which are a stalk or filament that supports the pollen-producing anther. The female reproductive organs, which are collectively called the pistil, consist of the ovary, where ovules are produced, and the style with its sticky surface on top called the stigma.
In angiosperms, pollination is defined as the placement or transfer of pollen from the anther to the stigma of the same flower or another flower. Pollination takes two forms: self-pollination and cross-pollination. If a flower has both male and female reproductive organs, it is referred to as bi-sexual, and it self-pollinates by a mechanism in which the anther opens up and the pollen lands on the stigma of the same flower or another flower on the same plant. This method of pollination does not require an investment from the plant to provide nectar and/or pollen as food to attract pollinators. For flowers containing only one set of reproductive organs, a pollinator (wind, water, animals, birds, or insects) is required to transfer pollen from the anther of one flower to the stigma of another flower on a different plant of the same species, a method known as cross-pollination.
Living species are designed to ensure the survival of their progeny, and those that fail become extinct. Genetic diversity is essential to a species in a changing environment or under stressful conditions. Progeny as a result of self-pollination have less genetic diversity since the same genetic material is being used time and time again. Cross-pollination has the opposite effect. It leads to greater genetic diversity because the offspring are created from genetic material of different plants within the same species. Clearly, cross-pollinators stand a better chance of being around for the long haul. A savvy cross-pollinating flower knows it has to have “the right stuff” in order to get the pollinators to come hang out with it long enough to get all covered in its pollen before flying off to hopefully another flower of its kind for a pollen transfer.
As mentioned earlier, flowers have some standard characteristics used for attracting insect pollinators, but what if those fail? Maybe a flower’s petals aren’t showy enough to get an insect’s attention or perhaps an insect doesn’t have a palate for pollen or nectar? Oh, no, what’s a flower to do?
With the help of evolution, some flower species upped the ante with shenanigans when it comes to attracting those discriminating insect pollinators. Some flowers, unabashed in their deviousness, mimic the smell of the food, such as coconut, or even rotting meat, that certain picky eater insects want. And, if tricking by way of food to get attention doesn’t work, the promise of sex probably will. Some flower species have evolved to resemble female versions of certain insects, a strategy known as insect mimicry. Perhaps the cleverest and most effective deception technique of all for these sneaky Pete flowers is to look the part of a desired insect mate. Orchids are the most notorious species for this type of pseudo-sex promise, a strategy that allows the species to spread its genes widely and works nearly perfectly for them. Case in point, the Australian hammer orchid has taken advantage of the thynnid wasp’s mating ritual which consists of a female wasp waiting on top of a branch or plant for a male to spot her. The hammer orchid’s flower mimics a female thynnid wasp, complete with a fake shiny head and furry body, as though sitting on a branch, looking upward waiting to be spotted by a male. But wait, the deception continues. It’s not enough to just look like a female wasp, the orchid even releases an enticing scent similar to the female wasp pheromone. Poor fellow, he doesn’t stand a chance. When the male wasp tries to mate with the dummy female, he fails, but the orchid succeeds in a big way by getting its pollen on the wasp. He flies away only to be duped again by another hammer orchid pulling the same trick. In this process, the wasp transfers pollen from flower to flower.
But, to give the male wasp some credit, when a real thynnid female wasp is next to the orchid mimic, the male wasp spots the real deal immediately. Because the impostor can’t ultimately win against the true female wasp, it is here where natural selection has favored the flowers that bloom during the period when male thynnid wasps are flying, but the females have yet to emerge.
Although not as consistent across all flowers in the species, the South African daisy also employs pseudo-sex trickery, but the insect it chooses to mimic is the fly. Petal colors in this species range from pale yellow to bright red-orange, and some petals have spots that form a circle around the flower’s center. There is great variety in the appearance of these flowers. In some, the spots on the petals have transformed into green-black bumps that to a fly look exactly like its female mate awaiting seductively upon the petals. Male flies don’t stay long on flowers with simple spots, but the insect Don Juans are most definitely convinced by these fake flies, ultimately spending more time trying to mate, and in the process getting more and more covered in pollen to either transfer to another flower or rubbing off more and more pollen onto the flower, helping to pollinate it.
Talk about masters of disguise, these floral outliers of fake foodies and fake mates have indeed gone to the top spot when it comes to getting what they want! Hopefully this article offered a different kind of perspective when it comes to flowers and their relationship with insect pollinators. With that next walk in nature, take not only a moment to smell the roses, but also notice the “attraction” characteristics across the varieties of flowers and see if any flowers are “buzzing” with insect pollinator activity.
by JD Harper
JD Harper is a local author. GLINT, her debut novel, is set in Chattanooga amid its rich Civil War history and rock climbing culture. You can email her at firstname.lastname@example.org.