A Couple of Botanists, Literally

November 19, 2003

By Andrew Vowles

Botany professors Christina Caruso and Hafiz Maherali share research space in the Bovey greenhouse.
Photo by Martin Schwalbe

Those scarlet and blue lobelia plants growing in a section of the Bovey greenhouse have been busy, if the fuchsia-coloured stalks clustered among them are any indication. The eye-catching hybrids are an appropriate metaphor for the mingled research interests and personal lives of their human progenitors.

Profs. Hafiz Maherali and Christina Caruso brought their complementary research and teaching interests in plant physiology and ecology to Guelph's Department of Botany in January. To judge by the matching gold bands both wear in idiosyncratic fashion on their right hands, that's not all they brought.

As the first married couple hired jointly into the department, the husband-and-wife team of botanists meets in his-and-her studies of plant parts and plant evolution. Seated in his first-floor office in the Axelrod Building - directly across the hall from Caruso's - Maherali grins as he says: " She's the flower person, I'm the leaf person."

Where physiology and ecology meet is on the common research ground of biodiversity, an increasingly hot topic among the assorted botanists, zoologists and molecular geneticists in offices and labs throughout the Axelrod Building.

"Their research fits nicely with a developing strength both within the department and in the College of Biological Science," says Prof. Richard Reader, chair of the Department of Botany.

Maherali notes that ecologists or evolutionary biologists are "all in some way trying to understand how biodiversity evolved, how did we get here. What's gained by the two of us working together is that we basically bring a whole-organism perspective."

He and Caruso, who are members of the Biodiversity Institute of Ontario planned for U of G, together hope to learn more about the push-pull between flower structure and plant physiology in influencing evolution, including studying a chicken-and-egg conundrum: Do evolutionary pressures on floral traits account for speciation of plants, or do physiological changes push those plants down separate evolutionary paths?

To answer those questions, they're studying two closely related species of lobelia. The red one, Lobelia cardinalis, is known among perennial gardeners as cardinal flower. Less common is its blue cousin, L. siphilitica (so-called because it was once thought to cure syphilis). Even more obscure is the fuchsia hybrid nestled among its parents in that Bovey greenhouse.

Different flower structures in the two parent species mean that various pollinators prefer one or the other. L. cardinalis attracts hummingbirds; L. siphilitica, bees. Whereas the red species prefers boggy ground, the blue one favours a broader range of wet and dry habitats.

Those differences offer varying but complementary possibilities for botanists. Where Caruso saw a candidate for testing ideas about adaptive pollination strategies, Maherali saw it as a study of drought tolerance.

They also find L. siphilitica intriguing because it's gynodioecious, meaning some plants carry female-only flowers, and others mix male and female functions on the same flowers. What were the ecological and physiological consequences of one or the other?

"It's an evolutionary question," says Caruso, who wondered why female-only plants hadn't been squeezed out by hermaphrodites with their twofold breeding potential. "They have to make up for a disadvantage."

Their study found that female-only plants compensate for their disadvantage through a physiological difference that allows them to run a higher rate of photosynthesis to turn sunlight into more food.

By cross-breeding the two species, she says, "I'm trying to capture the genetic basis of differences in floral and physiological traits. What percentage is due to genetic variation?"

This summer, the couple set up a joint experiment to examine the effects on floral morphology and physiology of growing the plants in either dry or wet conditions.

The duo might not have met at all if Caruso had followed her initial path. "I started as an ornithologist," she says. She studied both plants and animals at Oberlin College in Ohio. It was during a pollination study that she realized that what attracted her was not the pollinator but the "pollinatee."

Maherali was more interested in the physiology of plants - how they do what they do. A Calgary native who had studied the topic as an undergraduate at McGill University, he wanted to learn more about possible effects of global climate change.

With a graduate scholarship in hand, he headed off for PhD studies at the University of Illinois, where Caruso was studying pollination and floral evolution. They met over pizza one evening after a lecture on plant ecology.

Married in 1998 before graduation, they lived apart for two years after Caruso landed a post-doctoral fellowship at Grinnell College in Iowa and Maherali went to Duke University. After racking up numerous frequent-flier points and long-distance telephone bills, they were ecstatic when Caruso received a post-doctoral award to Duke from the American Association of University Women.

That long-distance experience led to their resolution to find joint postings at one university, a quest that saw both turn down promising individual offers. They hit gold with Guelph, where they now share lab space and are team teaching a graduate seminar course this semester.

"We end up talking a lot about science at home," says Maherali, adding that they often vet each other's research papers and grant applications. They say they aren't afraid to criticize each other's work. For relaxation, they've found another shared interest in tending the vegetable garden at their recently purchased Guelph home.

Presumably, they've figured out a more equitable division of labour there than during their school days. Becoming partners at Illinois and then Duke had paid unexpected mutual benefits. Each automatically got an extra pair of hands for lab or fieldwork, but the benefit wasn't necessarily even.

Maherali helped Caruso complete her dissertation on floral evolution, which meant he got to spend time in mountain meadows in Arizona. And what idyllic prospect did he dangle in return? "She helped me grind ponderosa pine needles at Illinois."