The incredible journey of pollen

Because most flowers are hermaphroditic, plant fitness often has both female (the number of offspring borne) and male (the number of offspring sired) components. Since it is easy to identify the mother of a seed, simply counting seeds from flowers allows us to determine the female component. However, very little is known about the male component because it takes paternity analyses to identify the fathers of seeds. But by tracking pollen grains from their source to their final destinations, much can be learned about the intricacies of the male fitness component. Unfortunately, this too has been difficult in the past because individual pollen grains are almost impossible to distinguish from one another, making it hard to know their origins. New technology, allowing us to label and track pollen grains has triggered a series of ‘thought experiments’ on how competition to fertilize a limited number of ovules may be shaping the male fitness pathway and the evolution of flowers. I would like to take you on a journey, the journey that pollen grains must make before they fertilize a seed. Along this journey, pollen grains must face a multitude of obstacles and most pollen grains are lost before they pass on their genetic information. I am interested in this journey because each obstacle represents an opportunity for natural selection to weed out pollen grains from the race and in so doing, hone plant traits that result in more efficient journeys. Some of the biggest obstacles may in fact be the presence of pollen grains from rival male flowers and I profess that flowers and their pollen grains are likely involved in previously unseen battles among one another which affect their ability to complete the journey. The ability of pollen grains to complete their journey can dictate how floral traits evolve, whether populations or species flourish or go extinct and whether you can have blueberries for breakfast or not.

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Kort biografie

Bruce Anderson has always loved fish, birds, snakes and anything creepy-crawly. It took him much longer to realize that plants are cool too. So cool in fact, that he has dedicated most of his career to studying them – especially their interactions with things that creep, crawl or fly. In his youth, he used to enjoy hitch-hiking to far-away places, including the University of Cape Town, where he completed his Bachelor of Science degree and PhD. He was a good hitch-hiker and remarkably was never late for lectures. Now he studies floral “stow aways”; that is, the seeds and pollen grains that catch unbidden rides with animals, embarking on journeys that often take them to unintended places. But because their animal-rides neither care what happens to them nor are they trying to do their passengers any favours, plants have have been forced to evolve a multitude of ways to flag down their animal rides and stay on them until they reach their destinations. Bruce is particularly interested in how interactions between different species can shape their evolution and behaviour, despite the fact that interacting individuals are seldom invested in each other’s mutual success. He marvels at the extraordinary diversity of life – continuously radiating as a product of entangled interactions within and between species. These radiations are set in the context of a dog-eat-dog world and are driven by an inherent will to survive, consume and reproduce.

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