Julia Ajello

No Evidence of Sexual Selection in Brassica rapa, a Hermaphroditic Plant

April 10, 2021   /  

Name: Julia Ajello
Major: Biology
Advisor: Dr. Jennifer Ison

The presence of sexual selection has been identified in animals since Darwin first wrote On the Origin of Species in 1859. However, it took much longer for this concept to be applied to plants. Two prominent mechanisms of sexual selection, female choice and male-male competition are evident in animals, but these same processes look very different in plants and they often take many different forms. Advantages to reproductive fitness are often incurred due to sexual selection, however, these effects are less well known in plants. In order to experimentally determine the influence sexual selection has on the reproductive fitness of a plant, I hand-pollinated flowers on Brassica rapa plants, a hermaphroditic annual. To indicate the presence of female choice, one or five sires were used to pollinate a single flower. Likewise, in order to simulate pollen competition, low or high pollen loads were also used to pollinate the plants. The seeds that the plants produced after pollination were counted as an indication of reproductive fitness. No evidence was found that supported the notion that sire number and pollen load size affected the number of seeds produced. Sire number and pollen load size also did not affect the probability of producing at least one seed. However, the maternal plants could better predict the number of seeds produced as well as the production of at least one seed. The differences due to maternal plant is a clear indication that maternal effect is playing a larger role on affecting the reproductive fitness of the plants used in this study versus female choice and male-male competition.

Julia will be online to field comments on April 16:
4-6pm EDT (PST: 1-3pm, Africa/Europe: late evening)

56 thoughts on “No Evidence of Sexual Selection in Brassica rapa, a Hermaphroditic Plant”

  1. Julia, this presentation was excellent! You made your project very easy to understand for us “non-science” folks. Congratulations!

    1. Hi Sanne! It’s a long story, but the short version is that in one of my early classes that I took at the college, we talked about sexual selection but only in the context of animals. That led me to think about how the concept of sexual selection can be applied to plants. Through my research, I realized that there was a big gap in literature concerning sexual selection in plants so I wanted to contribute to the field through an experiment!

  2. Julia, what a great accomplishment! Your presentation was interesting and easy to follow- even for those of us who know nothing about botany. Congratulations

    1. Thank you! I’m really glad you enjoyed it! One of my goals was to challenge myself to format my project in such a way that everyone could understand it.

  3. Great job Julia! It’s great to see the results from all your hard work in the greenhouse. Congratulations!

    1. Thank you! It was fun to work in the greenhouse and I appreciate all of the help you provided me in the greenhouse through the use of the space, supplies and expertise in plant care.

  4. Julia this was an awesome presentation! Congrats and amazing job, proud of you!

    1. Thank you! I really appreciate all of the support you have provided me throughout this year!

  5. Congratulations Julia! I really enjoyed your presentation – it is clean and comprehensive, and I really appreciate your explanation of the theory and methods for non-bio majors. What was your favorite part of investigating this research question? Also, do you expect that a plant species that is does not have reproductive organs for both sexes would have different results under similar experimental circumstances?

    1. Hi Tess! My favorite part of this project was contributing to a field that is understudied, and opening people’s eyes to the complexity of plants. As to your second question, I would think that similar results would be seen in plants that have separate biological sexes. Since hermaphroditic plants possess both male and female function, processes that take place in non-hermaphrodites will look much the same way as they do in hermaphrodites, they’d just be on the same plant. Usually processes of sexual selection affect either males or females, or the male or female function in plants, but one difference that arises due to hermaphroditism is that some processes affect both the male and female function. Sexual selection in hermaphrodites is a very interesting albeit an understudied field so it’s hard to know exactly how it would look in non-hermaphrodites.

  6. Great Job and Congratulations Julia! Before, I simply enjoyed the beauty and fragrance of a flowered plant. Now, I will be wondering if maternal effect is directing its reproductive fitness.

    1. Hi Kathee! One of the best things about this project is that it forces you to look at plants differently. Plants are much more complex than previously thought, so it interesting to learn more about the complex processes that take place in plants.

  7. Excellent talk! What a clear explanation of sexual selection and why it is so understudied in plants. What other traits would you want to study to look for sexual selection in plants?

    1. Hi Julia! I watched your talk early because I wrote down the time wrong. But I wanted to say ‘hi’ during your actual presentation slot. Great job!

    2. Hi Dr. Ison! Thank you for all of your help with this project! I would like to look for traits that would definitively show whether sexual selection occurred. For example, that could be the presence of pollen tubes that pollen create in order to reach the ovum. I think studying the offspring (the seeds) would have been interesting to see if traits relating to flower structure were selected for since flowers serve as a big indicator for sexual selection.

  8. Awesome job Julia! Do you think your results could be applicable to other species of plants?

    1. Hi Lydia, I would think that this could be applicable to other plants species. One big difference though, is the fact that Brassica rapa are hermaphrodites, and while it is extremely common in the plant kingdom, its hard to know what these results would look like in non-hermaphrodites.

  9. Great job! What do you think were the differences between the maternal plants that caused differences in the number of seeds they produced?

    1. Hi Maggie! Great question! It could be any number of factors that I would have liked to looked more into. For instance, the genes of the mothers due to variations between individuals could have caused differences that were passed on to their offspring. Even the environment that the mother was raised in and their phenotypes could influence the phenotype of their offspring which would have manifested in differences in their seeds. Without proper genotyping, it is difficult to know which factors were at play.

  10. Awesome presentation, Julia!
    Is there anything you would have done differently if you had more time?

    1. Hi Nicole! Great question because there are so many things I would have liked to do with more time. The biggest thing I would have liked to do was to do paternity tests on the seeds to see which fathers actually sired seeds. Even looking to see if certain paternal plants were chosen more than others and what traits they could have would have been very interesting to look at. Continuing the project so that more generations were looked at would have been beneficial to the project since fitness is better looked at through multiple generations.

  11. Congratulations, Julia! Your presentation was very well done and your research was really interesting!

    1. Hi mom! Thanks for stopping by! What surprised me the most is that the two key forms of sexual selection that we tested did not affect the fitness of the plants. It was surprising because many other studies that looked at sexual selection in plants did see differences to fitness.

        1. I would like to continue the study with the seeds that were produced to see if any changes to fitness continue in later generations or become more evident.

  12. Great job Julia! I really enjoyed hearing about your project! Has this project influenced the way you look at plants? For example, do you feel you are less likely to experience “plant blindness” because of this project?

    1. Hi Erica! Thanks for stopping by! I would like to think that this project really has opened my eyes to the complexity of plants. I think I’ll definitely be more aware of plants because of this project! I hope it has done the same for other people.

  13. Great presentation! I was wondering how you thought this data might change if the experiment were done outside. Do you think the presence of non-conspecific pollen or pollen from the same individual (resulting in self-incompatibility) would change the outcome?

    1. Hi Ren, thanks for stopping by! Excellent question! In the real world, i.e. outside, the type of pollen definitely would have changed the outcome. Brassica rapa are self-incompatible so if pollinated by pollen from the same plant, fertilization probably wouldn’t have occurred and seeds wouldn’t have been produced causing a huge detriment to fitness.

  14. Julia,
    Congratulations on all of your hard work. What an interesting topic and method. What surprised you the most about your findings?

    1. Hi Julie! Thank you! The most surprising thing about my study was that the manner in which we tested sexual selection did not cause differences to the fitness of the plants. Many previous studies have shown that female choice and male-male competition do provide differences, usually benefits, to fitness so it was surprising that the same was not found in my project.

  15. Great job Julia! I love seeing all the pictures of your plants and hearing about your process. I know this was a long process with a lot of watering, I’m glad to see your project turned out so well!

  16. Great presentation, I didn’t know much of anything about plants before this but I feel that I have learned just a bit about how much more complex plants can be than I first thought.

    1. Hi Michael! Thanks for stopping by! One of my main goals with my project was to open people’s eyes to the complexity of plants. Plants are capable of performing complex tasks so it’s interesting to learn about them and teach other people about them.

  17. Hi Julia, Great job! I learned a lot from your presentation. Congratulations completing such interesting research.

  18. Congratulations Julia! Thanks for sharing your research, it’s a very interesting topic!

      1. Whoops this was meant for my dad, which you are not. Still, thanks for stopping by and I’m glad you enjoyed the presentation.

  19. Your project is amazing! I can tell that you worked really hard on it, congratulations on finIShing 🙂

  20. As much as I love plants and gardening, this was a subject I never thought about. One day I hope I will get to see your garden as I’m sure it will be fabulous. Congratulations on completing your paper …. much love and luck for your future. (Kath’s grandmother)

    1. Aw thank you so much! I can only hope to have such a nice garden. If I do, I’ll be sure to show you and everyone!

Comments are closed.