Wendy R. Semski

3 photo panel. Left: a bumblebee (Bombus vagans) in mid-air next to purple flower (Mimulus ringens) on a soft green background. A stripe of white pollen is on the bee's face. Center: Side view of Wendy Semski, a white, late-20's female, examining a flower. Right: black-and-white scanning electron micrograph of about 25 Mimulus ringens pollen grains, some of which have pollen tubes emerging. A photograph of a population of Mimulus ringens in NE Ohio. Multiple many-stemmed flowering plants are visible in the foreground, with green plants blurring into the mid-ground and a tree-line is visible in the distance. A photograph of a bumblebee (Bombus vagans) with an orange pollen basket and stationary wings perched on a Mimulus ringens flower on a blurred green background. White pollen dusts the bees face.

Hello! I am a plant evolutionary ecologist
at UW-Milwaukee, USA

A photograph of a white, late 20's female with long light-brown hair, black-frames glasses, wearing a blue and black striped top. In the background, a field of wildflowers and trees are visible. The woman is smiling at the camera.

My name is Wendy Semski and I am a PhD candidate in the lab of Dr. Jeff Karron. My research focuses on understanding how patterns of flower deployment influence plant mating in monkeyflower (Mimulus ringens). This work is especially important in the face of climate change because plants' response to altered environmental conditions results in novel flowering times and patterns.

A cartoon of a purple flower resembling those of Mimulus ringens with two stylized green curving lines on either side.

Flowering phenology is the timing and duration of the reproductive period of angiosperms, and is critical for reproductive success and fitness. Plants must flower during the time when environmental conditions are optimal, and for many species, they must also match their flowering phenology with the activity of their pollinators. Flowering phenology is influenced by temperature, photoperiod, and moisture. Climate change has resulted in a decoupling of these environmental factors so that plants experience novel flowering conditions. It is critically important, therefore, to tease apart the environmental and genetic factors associated with the initiation and progression of flowering.

Watch my recorded talk for Asilomar 2021 below!

There is marked variation in when individuals within a population begin to flower and in how their flowering progresses over the season (called the flowering schedule). This variation may affect patterns of gene flow, which shape the genetic structure of populations. For example, plants that begin to flower early in the season are unable to mate with plants that flower later, and this is especially likely if flowering duration is short. Consequently, these plants may have limited mating opportunites and therefore mate assortatively. When few mates are available, matings are more likely to occur with inferior individuals, reducing their fitness through decreased offspring quality.

However, variation in the onset of flowering does not tell the whole story. Individuals within a population may deploy their flowers on very different schedules, leading to varying floral abundance. Asynchronous flowering is more likely when flowers are deployed sporadically and increases the probability of mating with plants with similar flowering patterns. If these patterns are heritable, then it is probable that these matings will occur with more closely related individuals. This can lead to fine-scale genetic structure and population divergence.

A graph depicting the flowering schedules for 20 plants from population MSB. Flowering day is on the x-axis, and the y-axis is organized by plant ID in ascending order by date of first flower. Rows of white circles represent a day on which a plant flowered, and the size of the circle represents the size of the floral display so that larger circles indicate larger displays. There is wide variation among plants in the date of onset, number of days in flower, size of floral displays, and duration of flowering.

A photograph of a Mimulus ringens plant with four purple flowers and many green leaves and branches on a black background.

The number of flowers open simultaneously on an inflorescence, called the daily floral display, affects the amount of among-flower, within-plant self-fertilization that occurs because pollinators are more likely to move frequently between flowers on the same plant. Selfing can be advantageous if mates are hard to find, but high levels of selfing causes the accumulation of genes that cause birth defects in the population. Therefore, producing few flowers at a time (but flowering for a long period) may be an adaptation to decrease this kind of selfing, and may be reflected in their branching architecture and patterns of bud formation.

There is a critical need to tease apart the genetic and environmental factors that influence flowering patterns. This can be done by implementing a "common garden" study, where plants from different populations are grown in the same environment and then measured. If this is done well, any differences between plants must be due to genetic differences.

My research goals are:

To understand the extent of variation in flowering phenology and patterns of flower deployment in a common garden
To determine if there is a relationship between floral display size and population selfing rates
To discover whether individual flowering schedules can be predicted based on plant architecture and patterns of bud formation