A research paper on the role of spines in seed dispersal was recently published in Ecology and Evolution. The authors: Dr. Marc Johnson, an associate professor of biology at UTM, his wife, Reagan Johnson, and their two school-aged kids, Mae and Oscar Johnson.
Johnson has been working on the Galápagos Islands since 2015. His original topic of study was the co-evolution between Darwin’s finches and the food they eat. “Finches can rapidly evolve and adapt to the environment, largely due to the distribution of seeds they eat. It’s one of our best examples in nature of rapid evolution, yet we know little about [the] plant ecology,” he explains.
The plant Tribulis cistoides produces a fruit that breaks into sections called mericarps. The finches must open up the mericarp to reach the seeds; however, mericarps have spines—which are parts of leaves and resemble thorns in their pointiness—to protect them from predation. The mericarp usually has four spines: two upper and two lower, although variations are also common. A bird’s beak size determines which mericarps it can easily open and which it cannot. Johnson’s research demonstrated that birds can impose natural selection on the seeds since they have less preference for mericarps with long or lower spines. However, Johnson also noticed that the variation in spine characteristics across the different islands was not consistent with predictions based on the predation pressure from the birds.
In January 2018, Johnson, his wife, and their children moved to the Galápagos Islands for Johnson’s research on how cities and towns influence the finches and plant ecology. Johnson and Reagan were homeschooling the kids, who, at the time, were twelve and nine years old, respectively. “[Reagan and I] thought this could be a great opportunity to actually do some science with the kids. It could be a part of their learning—their science and math and English and geography,” Johnson relates.
“I started asking the kids, ‘We know that the spines influence the birds, but do you think anything else could be important in influencing this? Do you think these spines could be involved in dispersal?’” Both Mae and Oscar did think that the spines were involved in the dispersal of the plants’ seeds, so Johnson probed further and asked them how the spines might me involved. After brainstorming sessions, “[Mae and Oscar] proposed that maybe the spines help[ed] the [plant seed] wedge into things like tires on cars or shoes.” Johnson then asked both kids “how can we test that?”
Together, Johnson, Mae, and Oscar designed three different experiments. First, they manipulated the spines to resemble those found in nature, by cutting either the upper pair, lower pair, or both pairs. They then tested the role of people’s shoes by walking over the mericarps, the role of towels on beaches by laying out towels over mericarps, and the role of cars by measuring how far the mericarps travelled on a road when they were driven over. In each condition, they recorded how far the mericarps travelled or how many mericarps were picked up by the shoe or towel. They began to see that the presence of upper spines increased seed dispersal in all three experiments. While Johnson carried out the advanced statistics for the research paper, Mae and Oscar formed their own conclusions by plotting and interpreting the data themselves.
The Johnsons also designed a fourth experiment in which they compared the seed dispersal rate in natural areas with the seed dispersal rate in areas of anthropogenic activity. They placed fifty mericarps in three different regions: roads, pedestrian walkways, and natural areas with limited human activity. The results showed that the dispersal rate was nearly 90 percent higher on the roads and walkways than in nature—effectively illustrating the role humans play in the dispersal of spines.
The paper describing the Johnson family’s research was published in the journal Ecology and Evolution in December 2019. Johnson shares that they “had a hard time getting the paper reviewed because [reviewers] could see [that the authors were] Johnson, Johnson, Johnson, [and] Johnson” and some reviewers tended to have false perceptions of the work. However, as Johnson explains, “most journal have criteria for authorship —typically individuals need to have significantly contributed to the ideas, research questions, methods, experimental design, collection of data, analyzing the data, and writing the paper, or at least to a couple of those.” While Johnson took the lead on the statistics and writing the paper, Mae, Oscar, and Reagan “not only met but exceeded the criteria.” Ecology and Evolution judged the article based on the quality of the science in the paper and decided to publish it.
“It is a solid and novel piece of scientific work that kids in grades seven and four were able to do, and that’s pretty special. It’s been a privilege to work with them,” Johnson says of the experience. He adds that work-life balance can be difficult, so this “was a once in a lifetime trip.”
Reagan Johnson’s favorite part of the research was when she “took the kids…to collect seeds and other data.” She says it “was neat to see them being real scientists.” Johnson’s son Oscar, who is now 11, loved “recording the data on the laptop” while Mae, who is now 14, says that the part she liked best was “where [the experiment] actually started working.” She explains: “We were doing a lot of experiments and we didn’t know if it would work or not. When we started getting conclusive results—that was kind of amazing because we had asked a question and we were actually making a discovery.”
Mae also remarks that “it was really nice because they were working with people [they knew] and so [she] really enjoyed it. The hardest part of it was being cooped up with the same people for six months, which can be really tough.” Overall, Mae thought that “it was a good experience. [They] got to know each other really well and got a lot closer.” Oscar also thought the experience “was kind [of] nice.” He quips, “We spent all this time together and we got really, really, really close – figuratively and literally.”
Reagan finishes off: “It was very special to share this unique experience. But it was difficult as well to walk the fine line between being a parent, a teacher, and a co-scientist/collaborator. Some days, we just wanted to go snorkeling.”