Research
Our world exhibits extraordinary (and beautiful!) natural variation. I aim to understand the evolutionary forces shaping this diversity, and its ecological outcomes, with a focus on plant reproduction. How does plant sexual diversity shift spatially and temporally?
My research so far has examined the evolution of kin discrimination in plants and floral plasticity in response to variable pollinator visitation. You can learn more about each of these projects below.
Kin discrimination
STUDY SYSTEM: MIMULUS GUTTATUS
Illustration: Mimulus, by me.
Many species live in dynamic communities where they interact closely with the neighbours that surround them. The outcomes of these interactions can depend on the identity of neighbours – for instance, competitive responses may benefit the individual but compromise inclusive fitness if the surrounding neighbours are kin. In these cases, altruism towards relatives may evolve instead. While plants recognize and respond to the presence of kin, research into altruistic kin responses in plants remains limited. Do plants exhibit kin discrimination, and what do those responses look like?
To answer this question, I grew plants of Mimulus guttatus, a model species that reproduces both florally and clonally, in the greenhouse in pots surrounded by unrelated or sibling neighbours. To examine how floral and clonal growth might respond simultaneously, I measured responses in each. I found that plants decreased both floral and clonal growth when neighbouring siblings. While competitive increases in growth may increase direct fitness (i.e., floral through increased pollinator visitation, and clonal through increased use of resources and space), they are also costly investments. Reduced competition amongst kin may allow plants to simultaneously avoid indirect fitness losses while increasing direct fitness, through greater investment in reproductive output.
Identifying the selective pressures shaping interactions within plant neighbourhoods allows us to understand how communities persist in space and time. If kin discrimination increases the success of highly-related patches, it may result in spatial structuring of genetic diversity within populations. This research characterizes the nature and consequences of kin discrimination in plants, giving insight into plant neighbourhood dynamics.
Paper in progress!
Photos, in order: Early days, central focal plant surrounded by four neighbours. / Hectic flowering, innumerable visions of phenotyping in my dreams... / Neighbours in a pot, all grown up.
Floral plasticity
STUDY SYSTEM: SAPONARIA OFFICINALIS
Illustration: top, male-phase Saponaria; bottom, female-phase. By me.
For animal-pollinated plants, interactions with pollinators present a crucial selective pressure for floral traits. Flowers must mediate investment in advertisement traits with reproductive ones – including, for hermaphroditic flowers, balancing pollen donation, pollen receipt, and setting seed. The returns from these allocative choices differ with pollinator visitation, which is often dynamic – across ranges, years, and seasons. Thus, plasticity in these traits may be essential to reproductive success. How do floral advertisement and sex allocation shift under variable pollinator visitation?
To test this, I used Saponaria officinalis, an invasive weed with protandrous flowers that undergo a colour change as they change sex. Flowers begin as white in male phase, before transitioning to female phase and turning pink. In a common garden at the Queen’s University Biological Station, I manipulated the level of pollinator visitation and measured flower colour and sex phase transition responses. This was conducted across two field seasons – in 2022, I manipulated pollen removal from male-phase flowers and in 2023, pollen deposition on female-phase ones. Male-phase flowers with high pollen removal accelerated the transition to female phase and were pinker at three days following treatment than their counterparts with no pollen removal. Likewise, female-phase flowers with high pollen deposition were pinker in the days following treatment than flowers with no deposition.
Larger floral displays can increase fitness by increasing pollinator visitation, yet are costly to produce. Retaining colour-changed flowers may allow plants to increase display size from long ranges. At close range, provided that pollinators can discriminate based on colour, these changes can direct pollinators to more rewarding flowers. Colour change may be then most important for male-phase flowers, where pollinator visitation increases reproductive success linearly. Under low pollen removal, for example, staying whiter may allow flowers to increase pollinator visitation. Alternatively, anthocyanins may also protect maturing ovules from sun damage. Thus, colour change could occur in respond to pollen deposition or fertilization, with implications for female fitness.
Pollinator visitation and resulting fitness outcomes may vary greatly annually and seasonally, as well as between individual plants or even between flowers of a single plant. Quantifying the capacity of flowers to respond to this variation helps us understand how plants cope with changing environments, and predict future outcomes as pollinators decline.
If you’d like to read my undergraduate thesis on the first half of this project, feel free to send me an email!
Photos, in order: Flowers bagged to prevent pollinator visitation. / Common garden grid. / Colour variation in early male-phase flowers.