Integrative Taxonomy in Camassia
CamasCamassia (wild hyacinth or camas) is a species complex which is distributed across North America and which contains taxa with widespread morphological and ecological variation. Several species and subspecies also occur in areas of sympatry with hybridization potential, thus often creating confusion in terms of the taxonomy of this group. We are using the camas system to examine the question of "What is a species?" using an integrative taxonomical approach. Working with Drs. Susan Kephart and Kathryn Theiss of Williamette University and Dr. Jenny Archibald at University of Kansas, we are examining species delimitation using several different approaches: morphometric analysis, phylogenetics, reproductive studies, ecological niche modeling, and population genetics/gene flow studies.


Genetic and Ecological Effects of Urbanization
woodlotCincinnati is a highly urbanized environment and consequently is ideal for examining effects of urbanization, such as habitat fragmentation, introduction of invasive species, and air pollution. Past research with violet species (Viola pubescens,V. canadensis and V. pedunculata [in California]) has focused on measuring the effects of fragmentation of natural areas on population-level genetic variation as well increased genetic differentiation. More currently, we have been working with Drs. Guy Cameron and Arnie Miller to quantify effects of the urban gradient on vegetational composition and diversity across southwestern Ohio. Our lab is also working with environmental engineers, Drs. Tim Keener and Mingming Lu to examine the effects of particulate matter (a major contributor to smog) on the health and reproduction of plant species.
The Evolution of Dioecy in the Hawaiian Genus Schiedea
SlogobsaBreeding system evolution is also the subject of my research with Schiedea, a genus that has undergone extensive radiation in the Hawaiian Islands and contains a full range of breeding systems - including hermaphroditism, gynodioecy (co-occurrence of females and hermaphrodites), and dioecy (co-occurrence of females and males). I have previously worked with Drs. Stephen Weller, Ann Sakai, and Diane Campbell on a quantitative genetics experiment in which we conducted artificial selection to study the genetic potential for sex allocation shifts to male and female function in two gynodioecious species, Schiedea salicaria and S. adamantis. Many traits associated with increased male and female function have a heritable basis and thus may contribute directly to the evolution of dioecy. In addition, we also measured the quantitative genetics of ecophysiological traits using plants from our initial crossing program for both species. We found that some ecophysiological traits are heritable, but only in certain sexes within different species. This is of particular importance because the heritability of ecophysiological traits have rarely been measured on the scale of our study. We are now continuing to use microsatellite markers we developed to examine issues of population genetics, migration rates, and gene flow.

Invasiveness in the Callery Pear (Pyrus calleryana)

pearThe Callery Pear (Pyrus calleryana) was originally introduced into the United States from China in the early 1900's as a rootstock species and as a source for fireblight resistance. It has quickly become one of the most popular ornamental tree species planted in urban areas. Known as the 'Bradford', 'Aristocrat', 'Cleveland Select', etc. (see list), these cultivars are highly desired for their springtime display of white showy flowers, vibrant fall leaf color, and tolerance of excessive drought and pollution. Within the last decade, wild Pyrus calleryana have begun appearing and multiplying in natural areas. Furthermore, many cultivated Callery Pears in urban yards have also begun producing fruits even though each cultivar is self-incompatible. Many of these fruits are dispersed by introduced birds such as starlings. In our lab, we are studying why Pyrus calleryana is beginning to spread and becoming invasive. Based on a combination of ecological and genetic studies, we now know that the recent expansion of Callery pear is due to intraspecific hybridization between different cultivars as well as rootstock. We are continuing to study this intriguing species to understand what impacts it may have on ecosystem processes as well as to develop practical suggestions for management of invasive populations. Our most recent work explores the effect of photosynthetic ecophysiology on the spread of the species in the US.

The Evolution and Expression of Cleistogamy in Violets (Viola)

CHCLMany Viola species have mixed mating systems because they produce both open, chasmogamous (CH) flowers and closed, cleistogamous (CL) flowers on the same individual. CH flowers are often assumed to be outcross-pollinated while CL flowers are automatically self-pollinated. One purpose of my research in Viola is to determine why these two very different types of flowers are produced, using two violet species found in the northeastern United States, Viola pubescens and V. canadensis. Contrary to the assumption that showy CH flowers are primarily outcross-pollinated, CH flowers exhibit delayed selfing and are capable of variable levels of selfing. In addition, levels of inbreeding depression are low in CH flowers, which appear to be responsible for a larger portion of seed production than CL flowers. In general, the dual system of chasmogamy and cleistogamy in Viola is a means of adapting to unpredictable pollinators in the early spring (through outcrossing of CH flowers) and to a lack of pollinators during the rest of the season (through CL flowers).

Molecular Marker Development

GelI am continue to be interested in the development of laboratory techniques which can promote key advancements in the plant sciences. For example, we have developed microsatellite markers for a wide number of species, including V. pubescens, Schiedea adamantis, Rhamnus cathartica, Monotropa hypopitys, and Spiraea virginiania, as well as devloping various DNA extraction protocols.  For protocols of all types used in our lab, see the Protocol Page...


Last Updated: May 1, 2014