Katrina Degenhardt
(PhD Candidate)
Pollinator-mediated selection on
floral traits in a buzz pollinated plant
Most flowering plants depend on foraging animals to facilitate gamete dispersal. Floral design and display traits that promote pollinator attraction are therefore thought to be a primary driver of floral diversity and should be subject to pollinator-mediated selection. However, pollinator attraction is only one component of the pollination process. In addition to traits that influence pollinator attraction, some floral traits may influence pollination efficiency via morphological fit between floral reproductive parts and the pollinator’s body. These functional traits can influence the quantity of pollen deposited onto the stigma as well as the quality of pollen deposited, such as the proportion of self and outcross pollen. Since traits that influence pollinator attraction and traits that influence pollination efficiency both contribute to reproductive success, it is important to measure selection on both types of traits. However, few studies have measured selection on such morphological traits not directly involved in pollinator attraction.
My research explores pollinator-mediated selection on both functional traits and pollinator attraction traits in a buzz pollinated prairie plant. Primula meadia (eastern shooting star) offers an ideal system to study how variation in floral morphology affects reproductive success. This wetland perennial is native to wet or wet-mesic prairies across central-eastern North America and is pollinated primarily by bumble bee queens. It is nectarless, offering only pollen as a reward, and flowers early in the spring when pollinator abundances are low. Theory predicts that selection on floral traits will be especially intense when pollinator services are insufficient and seed production is strongly pollen-limited, and in my study populations I have found a very high level of pollen limitation. To measure reproductive success and link it to certain floral traits, most studies compare seed set in open pollinated flowers and pollen supplemented flowers. However, this only describes reproductive success in one part of the pollination process. By quantifying visitation, pollen receipt, and seed set, I am able to examine reproductive success throughout the whole pollination process.
My research explores pollinator-mediated selection on both functional traits and pollinator attraction traits in a buzz pollinated prairie plant. Primula meadia (eastern shooting star) offers an ideal system to study how variation in floral morphology affects reproductive success. This wetland perennial is native to wet or wet-mesic prairies across central-eastern North America and is pollinated primarily by bumble bee queens. It is nectarless, offering only pollen as a reward, and flowers early in the spring when pollinator abundances are low. Theory predicts that selection on floral traits will be especially intense when pollinator services are insufficient and seed production is strongly pollen-limited, and in my study populations I have found a very high level of pollen limitation. To measure reproductive success and link it to certain floral traits, most studies compare seed set in open pollinated flowers and pollen supplemented flowers. However, this only describes reproductive success in one part of the pollination process. By quantifying visitation, pollen receipt, and seed set, I am able to examine reproductive success throughout the whole pollination process.
Wendy Shelton
(PhD Candidate)
Exploring the causes and consequences
of variation in flowering patterns
The timing and duration of flowering (flowering phenology) is crucial to reproductive success because it determines the number and identity of potential mates. However, most studies examine singular components of flowering phenology in natural populations, such as date of flowering onset or total flower number, and fail to account for temporal variation in flowering schedules among individuals. Studies of among-plant variation in patterns of flower deployment can provide important insights concerning mating patterns, especially the extent of among-flower, within-plant self-fertilization.
In this study, we raised individual plants grown from seed from 9 natural populations of Mimulus ringens in a common garden. M. ringens is a wetland perennial native to central and eastern North America, and plants produce flowers that last for only half a day. We recorded the daily floral display for the duration of the flowering period for 20 individuals from each of the 9 populations. We then analyzed the components of flowering phenology, including date of flowering onset, total flower number, flowering duration, and flowering synchrony. Individual flowering schedules and components vary widely within and among populations in the common garden. Plants that flower early also flower for longer and therefore have greater fecundity. Within populations, individuals are asynchronous in their peak flowering, which may reduce mate diversity and effective population size.
In this study, we raised individual plants grown from seed from 9 natural populations of Mimulus ringens in a common garden. M. ringens is a wetland perennial native to central and eastern North America, and plants produce flowers that last for only half a day. We recorded the daily floral display for the duration of the flowering period for 20 individuals from each of the 9 populations. We then analyzed the components of flowering phenology, including date of flowering onset, total flower number, flowering duration, and flowering synchrony. Individual flowering schedules and components vary widely within and among populations in the common garden. Plants that flower early also flower for longer and therefore have greater fecundity. Within populations, individuals are asynchronous in their peak flowering, which may reduce mate diversity and effective population size.