People in the lab
Laura F. Galloway
Holly R. Prendeville
2012 Summer research position
prospective graduate students
CURRENT RESEARCH PROJECTS
Maternal effects on life history
Parents may influence their offspring through genetic
and environmental factors. We are using two approaches to evaluate intergenerational
effects on life history evolution in the native wildflower Campanulastrum americanum (until recently Campanula
americana). Our work focuses on the timing of seed germination because
C. americanum seeds that germinate in the fall grow as annuals while
those that germinate in the spring become biennials. Therefore maternal
effects on germination timing will influence life span, fecundity and patterns
|| Parental Environmental Effects
Etterson (Univ. of Minnesota, Duluth)
Maternal and paternal environments may influence offspring characters.
We found that parental light levels influence offspring germination
and life history in Campanulastrum americanum. Offspring have three times greater fitness when grown in their maternal light environment than an alternate environment, indicating that maternal effects make a substantial contribution to adaptive evolution.
Effect of Maternal Phenology on Offspring
with Kevin Burgess (Columbus State University)
Timing of flowering influences the timing of
fruit maturation in C. americanum. Seeds from early season flowers
ripen before those of later season flowers and have a greater potential
to germinate in the fall as annuals. Therefore selection favoring
the annual life history may act to either alter timing of seed germination
or timing of flowering. We created early and late flowering
individuals with artificial selection and environmental manipulation to determine the extent to which
flowering time influences whether offspring grow as annuals or biennials.
Maternal Genetic Effects
with Julie Etterson (Univ. of Minnesota, Duluth) & Joel McGlothlin (UVA)
Evolution may occur if phenotypic variation has a genetic basis. That genetic variation may be due to an individual's own genes, refered to as direct genetic effects, or to genes expressed in the maternal generation. For example, maternal genetic effects strongly influence yolk volume and hatchling size in fish. Although maternal genetic effects are expected to dimish with age, we found both direct and maternal genetic effects influence traits throughout the life cycle in Campanulastrum americanum. In addition, correlations between traits both within- and between-generations influence the evolution of C. americanum's polymorphic life history.
Evolution of Polyploids
Polyploidy, a doubling of the
chromosome number, is a very common evolutionary change in plants. In particular autopolyploidy (within species chromosome doubling), results in changes in the amount, but not the type, of nuclear genetic material. Having twice as much genetic material may influence the evolution of polyploid species. For example, polyploids are predicted to have reduced levels of inbreeding depression relative to diploids because the probability of expressing recessive deleterious alleles is much lower if there are four alleles at a locus instead of the two present in diploids. Similarly, polyploids may accumulate genetic differentiation among populations more rapidly than diploids if either mutation accumulation increases with more loci or genetic changes in the "extra" gene copies are less likely to be removed by selection. We are conducting studies to address these ideas.
Polyploidy & Mating System
Campanulastrum americanum is insect-pollinated and self-compatible. Although there is a greater potential for selfing from within plant pollen movement in larger biennials, population-level selfing rates are negligible suggesting mating system does not differ between annuals and biennials. Inbreeding depression measured in three sequential cohorts in the field resulted in selfed offspring having only 6% of the fitness of outcross progeny. Cryptic self-incompatibility appears to maintain high outcrossing rates and inbreeding depression in this self-compatible species. High levels of inbreeding depression are surprising in this autotetraploid as theory predicts polyploids will have reduced inbreeding depression relative to diploids.
Polyploidy & Population Differentiation
with Sheri Church (George Washington Univ.) & Karen Barnard (UVA, below)
Populations in separate locations may differ from one another due to a combination of natural selection and genetic drift. In autotetraploid C. americanum first generation (F1) hybrids between nearby populations express hybrid vigor, outperforming their parents, while hybrid inferiority is expressed in crosses between more distant populations. F2 hybrids had greater outbreeding depression than F1 in some cases and less in others. Both cytoplasmic and nuclear genes contribute to this outbreeding depression. Outbreeding depression is unusual in first generation within-species hybrids. We currently gaining further insight into these unexpected results by expanding the spatial scale and complementing the phenotypic studies with genetic analyses. Previous work with Charles Fenster (Univ. of Maryland) found hybrid vigor in F1 crosses and hybrid breakdown in F3 hybrids for populations of diploid Chamaecrista fasciculata separated by 100m to 2000km.
Range expansion in Japanese Honeysuckle: Intraspecific hybridization?
I study range expansion in the invasive vine Japanese honeysuckle (Lonicera japonica). In a set of common gardens I looked at whether honeysuckle populations from the northern range margin (established within the last 65 years) and older core populations (established 100-150 years ago) have adapted to conditions in the core and at the margin of the range. My findings indicate that margin populations have evolved an invasive phenotype that has higher survival and grows to greater size regardless of garden location. I am currently testing whether margin populations also perform better than core plants beyond the current range margin. I used population genetics approaches to determine how genetic variation is distributed between populations and regions, the level of admixture of populations and the degree to which horticultural varieties have contributed to the genetic make-up of the invasion. Preliminary results indicate that a high level of genetic diversity has been maintained at the invasion front and that admixture is common throughout the range. I am collaborating with undergraduate and graduate students to look at 1) cold tolerance in invasive honeysuckle; 2) the role of intraspecific competition in the invasion process; 3) and whether a niche modeling approach can predict future spread of honeysuckle in North America, particularly in the face of climate change.
Selection for mate choice
Ashley Can Dai
I am interested in sexual selection in plants. Sexual selection has been studied extensively in animals but has received less attention in plants. This is partially because plants don't have active behavior making sexual selection unlikely to be analogous to animals, and most plants are hermaphroditic and it is difficult to tease the contribution of selection to male and female function apart. I am using the passion flower (Passiflora incarnata), which is functionally andromonoecious, to explore how sexual selection plays a role in floral trait evolution. In particular, which floral traits experience sexual selection? Is sexual selection important in maintaining andromonoecy? Does sexual selection change in pollen-limited environments?
Population differentiation and outbreeding depression in Campanulastrum americanum
I am a first year graduate student, having recently completed my Masters in Environmental Sciences at the ETH in Switzerland. My masters work focused on the population genetic structure of an alpine caddisfly (Allogamus uncatus). Currently I am interested in the causes and consequences of outbreeding depression in plants. I plan on exploring this phenomenon by developing a project to examine outbreeding depression and population genetic structure in the American Bellflower (Campanulastrum americanum), with a focus on cyto-nuclear interactions. Initial studies have shown high levels of outbreeding depression in between population crosses of C. americanum, with asymmetrical hybrid fitness. I would like to determine how general this pattern of outbreeding depression is across C. americanum's range and whether it is correlated with population genetic structure.
Past lab members....
||My project compares C. americanum populations from the northern and southern edges of the species range. Plants may grow as annuals or biennials and I am focusing on traits that may influence life history schedule.
| Lidia Mikolaenko
F1 hybrids between Campanula rotundifolia from European and North American were very vigorous, despite the great distance between the parental populations. I am evaluating whether F2 hybrids between these tetraploid populations express outbreeding depression or hybrid vigor.
||Tim is evaluating population differentiation for greenhouse grown plants collected from throughout the species range. Of particular interest is differentiation in germination and flowering time as this may influencelife history schedule.
|A. Catherine Pham
||The invasive vine Japanese honeysuckle (Lonicera japonica) is believed to have been limited in its northward expansion by cold temperatures. Catherine found plants from the northern margin were more likely to survive freezing temperatures than those from the core of the distribution suggesting the evolution of cold tolerance in this invasive weed.
||Campbell's project addressed how invasive species spread using Japanese honeysuckle (Lonicera japonica) as a model organism. Using DNA markers he found there was no differences in the frequency of sexual reproduction and vegetative spread between the center and the edge of Lonicera‘s range.
|M. Brett Jones
||Maternal flowering time and individual germination time determine whether C. americanum grow as annuals or biennials. Brett found low elevation population both germinate and flower earlier than high elevation populations. This suggests that the frequency of annual and biennial life history schedules may differ between elevations.
Contact Laura Galloway (email@example.com)
if you are interested in graduate studies or undergraduate research at
UVA or Mountain Lake Biological Station
Evolution & Population Biology, University
Biology Department, University of Virginia
Mountain Lake Biological Station