by José Montalva @josemmontalva
From our series “Friends of the Valdivian Rain Forest”, today, we bring “The Beauty and the Beast”, reminiscent of the classic French tale “La Belle et la Bête”, where our Belle, is with her stylized figure and red-purple dress, the beautiful Flower of the chilco (Fuchsia magellanica) and the Beast, this time using another meaning of the term – that speaks of how monstrous it becomes to its size and its heavy and clumsy flight – is our beloved bumble bee (Bombus dahlbomii). In our history, these two characters are faced with the problem of a third party; in our version, Gaston is the European bumble bee (Bombus terrestris).
Mutualistic relationships in ecological terms are those in which different species obtain mutual benefits from their interactions. In the case of pollination, the plant obtains a potential aid in fertilization; in return, a pollinator obtains resources, either nectar or pollen coming from the plant¹. That is the simple tale (and passed down for thousands of years) involving our protagonists.
The arrival of the European bumble bee (B. terrestris) interrupts this union. Pollination in many cases depends on a match, a fit between the interactors, whether morphological, phenological or ethological. This is why pollination can often not be carried out, even though there are actors (flower- flower visitor). ” There is simply no feeling”; no co- adaptation.
In the case of the European bumble bee morphologically, it is not adapted to the chilco; it has a too-short tongue and so is unable to reach the nectaries of the flower to gain that sweet resource. But, B. terrestris has an alternative, it has mandibles strong enough to break the corolla and thus reach nectar, an act known as nectar robbing ². In this action, B. terrestris uses the flower* and its resources and does not pay for its nectar by not pollinating the flower. It furthermore, leaves it without nectar for when its co-adapted pollinator arrives.
In a study by a researcher from the University of Washington, it was observed that B. terrestris, by stealing the nectar of the chilco and not pollinating the flowers, directly affects the fitness of the plant. The plant produces fewer fruits and fewer seeds. this short-medium term will be having an impact on the populations of F. magellanica³; in other words, when fewer seeds are produced, fewer plants will be generated in the future, potentially leading to population extinction. In addition, the nectar resource is reduced for future visits of the native bumble bee (or other true pollinators). During the study period, it was observed that the frequency of visits of the introduced bumble bees was 10 times greater than the one of the native bumble bee on the flower of the chilco. Apparently, this dynamic is maintained or has increased subsequently4. No doubt, conservation measures are needed, regulating the importation and indiscriminate sale of the introduced bumble bees. If everything continues as it has hitherto; then, this beautiful story will definitely not end with the classic phrase “and lived happily ever after.”
* Occasionally, when the corolla is broken, there is also a rupture of the ovary (leaving the flower unable to produce fruit – or post-plant infections mediated by fungi and viruses.
** stamens contain the pollen (the male gametes of the plant), upon arrival on a con-specific stigma surface (part of the female part of the flower), pollination occurs; they then grow down the style through and the arrive at the ovule at which point fertilization may occur.
1 Medel R., M. Aizen & R. Zamora (2009) Ecología y Evolución de Interacciones Planta-Animal. Editorial Universitaria, S.A. Santiago de Chile. ver
2 Leadbeater E & L. Chittka (2008) Social transmission of nectar-robbing behaviour in bumble-bees. Proc Biol Sci. 275(1643): 1669–1674. ver
3 Combs J (2011) Predispersal seed predators and nectar robbers: the influence of plant and animal traits on plant reproduction and bumblebee foraging behavior Ph.D. Thesis. Washington University, Washington, USA.
4 Valdivia, C. E., Carroza, J. P., & J. I. Orellana (2016). Geographic distribution and trait-mediated causes of nectar robbing by the European bumblebee Bombus terrestris on the Patagonian shrub Fuchsia magellanica. Flora. 225, 30-36.
El Ataque del Bombus. Comic Científico Par Explora Los Lagos ver