While most species have a single type of leaf shape, other species display a beautiful diversity in leaf shape. One such species is the sweet potato, where leaves of one variety can be so strikingly different from another that they can be confused as different species altogether. 

Sonal Gupta, graduate student in ecology and evolutionary biology, is studying leaf shape variation in sweet potato and how this variation may influence below-ground yield as part of her dissertation. Her research was published in New Phytologist, October 25, 2019. “Our research on 68 different varieties of sweet potato found that most of this leaf shape variation is due to leaf dissection and length-to-width ratio,” wrote Gupta. “We likewise found that leaf dissection and the length-to-width ratio are mostly controlled by genetic rather than environmental factors. Contrastingly, the environment was found to be highly influential when using more comprehensive measures of leaf shape. In the same study, we identified candidate genes associated with the variable leaf shape types, which could potentially help guide future crop breeding programs on this species.” 

Coauthors are her advisor Professor Regina Baucom, David M. Rosenthal, Department of Environmental and Plant Biology, Ohio University, and John R. Stinchcombe, Department of Ecology and Evolutionary Biology, University of Toronto.

The rhizotron greenhouse experiment. Each rhizotron was maintained at a thirty degree angle with the use of custom built wooden frames. Image credit: Sara Colom

Another paper from the Baucom lab looks at how belowground root-root competition influences plant diversity and evolution. “Roots provide structural support and likewise play a key role in nutrient and water acquisition from the soil,” according to EEB graduate student Sara Colom, who’s performing the research as part of her dissertation. “Roots are also key in mediating belowground plant-plant interactions. Despite these important ecological and functional roles, however, research on if and how belowground competition may influence the evolution of root traits remains relatively uncharted territory.”

Colom’s research with advisor, Baucom, fills this gap by addressing the potential that belowground competition acts as an agent of selection on root traits. They performed a series of greenhouse and field experiments at the Matthaei Botanical Gardens in Ann Arbor, Mich., using two sister species of morning glories (Ipomoea purpurea and Ipomoea hederacea) as their model system. The study was accepted in November 2019 and will be published in April 2020 in The American Naturalist. 

“We found that belowground root phenotypes varied between species – with I. hederacea being wider than I. purpurea, and I. purpurea exhibiting lateral roots that are more angled toward the soil surface than I. hederacea – but that there was still significant phenotypic overlap between them, such that they likely compete for the same resources when growing in close proximity. We also found evidence for genetic variation underlying root traits, and that competition between the two species negatively influenced fitness in field conditions. Importantly, we found that belowground competitive interactions between the two species altered the pattern of selection on root traits differently in each: competition with I. purpurea changed the pattern of selection on root angle in I. hederacea, and competitive interactions with I. hederacea changed the pattern of selection on root size in I. purpurea.

“Overall, this research shows that belowground competition can have important implications on plant diversity and evolution, and highlights that research on the evolutionary ecology of root traits has long been overlooked,” wrote Colom.

Read more from the American Society of Naturalists

Compiled by Gail Kuhnlein