Ruth Kirkpatrick

Dissertation Summary:

My research interests are in evolutionary processes, history, and phylogenetic relationships among green plants, especially ferns. I use molecular, cytogenetic, morphological, and physiological data to help resolve the phylogeny of ferns. For my dissertation I plan to investigate the phylogeny of the traditionally problematic fern genus Pellaea sect. Pellaea whose members predominately occupy dry and rocky habitats. Many of the ferns of this genus show extraordinary morphological and physiological adaptations to xeric habitats. My research goal is utilize these data in order to elucidate the adaptive evolutionary history of ferns to xeric environments.

Previous Research Projects:

My research experience has been primarily during my graduate study while earning a Master's of Science degree in Botany at Washington State University. This research was accomplished under the guidance of Dr. Pamela Soltis, Dr. Douglas Soltis and Dr. John Thompson and focused on the analysis of the mating system of the homosporous fern Gymnocarpium dryopteris ssp. disjunctum. Homosporous pteridophytes are unique among vascular plants because they reproduce via free-living, potentially bisexual gametophytes. Because of the potential for intragametophytic self-fertilization, this extreme form of inbreeding was regarded as the predominant mating system of homosporous pteridophytes. However, conformance to Hardy-Weinberg expectations, suggesting random matings, has been reported for the majority of pteridophytes analyzed electrophoretically. Although mating systems have been investigated in numerous seed plants, relatively few fern species have been examined. To determine the mating system of Gymnocarpium dryopteris ssp. disjunctum, I electrophoretically analyzed 15 natural populations of sporophytes. All 15 populations were highly outcrossing, and mean values of intragametophytic selfing, F, and mean heterozygosity for the 15 populations were 0.000. -0.072, and 0.186, respectively.

To determine factors that promote outcrossing in G. dryopteris ssp. disjunctum, I examined ontogeny, antheridiogen production and response, and inbreeding depression of cultured gametophytes. In multispore cultures, large meristematic female gametophytes and small ameristic male gametophytes are initially established with the potential over time for either sexual type to develop into functionally bisexual gametophytes. This developmental sequence promotes intergametophytic mating and suggests antheridiogen activity. Most pteridologist agree that antheridiogen activity promotes intergametophytic matings in laboratory cultures of gametophytes, and increasing evidence indicates that it may also promote outcrossing in nature. Significant positive responses of gametophytes of G. dryopteris ssp. disjunctum and Onoclea sensibilis to treatment versus control media suggest that antheridiogen activity may be an important factor promoting outcrossing in natural populations of G. dryopteris ssp. disjunctum. The maintenance of a genetic load in G. dryopteris ssp. disjunctum was exhibited by significant differences in mean sporophyte production among mating treatments of variously related gametophytes. Furthermore, the number of lethal equivalents per zygote (10.35 to 11.35) also indicates a large genetic load in populations of G. dryopteris ssp. disjunctum. A genetic load of this magnitude should promote outcrossing in natural populations.

Electrophoretic data provide evidence for an outcrossing mating system in G. dryopteris ssp. disjunctum. Factors promoting outcrossing in this taxon include gametophyte ontogeny, an antheridiogen system and genetic load.

My graduate research described here was published in my thesis submitted in partial fulfillment of the requirement for my degree of Master of Science in Botany at Washington State University in August 1988. I presented these research results during a talk at the American Institute of Biological Sciences meetings at UC Davis in August 1988. Portions of this research were published in two articles, one entitled "Antheridiogen production and response in Gymnocarpium dryopteris ssp. disjunctum". Kirkpatrick, R. E. B. and P. S. Soltis. 1992. Plant Species Biology 7:1-9 and another in the American Journal of Botany, 77:1101-1110, 1990, entitled "Mating system and distribution of genetic variation in Gymnocarpium dryopteris ssp. disjunctum" by Kirkpatrick, Ruth E. B., Pamela S. Soltis, and Douglas E. Soltis. Please note that I have included a reprint of this second article in my application packet.

I was peripherally involved with floristic research while attending the University of Wyoming in Laramie. During the Summers of 1983 and 1984 I was a volunteer field assistant with a Rocky Mountain Herbarium floristic study in the southeast Absaroka Mountains of northwest Wyoming. I participated in field collection, pressing and drying of more than 10,000 plant specimens. During the school year I was employed by the Rocky Mountain Herbarium as a herbarium aide and performed a variety of duties.

As an instructor at Mendocino College I have developed and taught several plant inventory field courses with the purpose of collecting, preserving and inventorying native plants on college owned lands. Students participated in hiking through more than 1800 acres of oak woodland, mixed evergreen forests, riparian habitats, grasslands and coastal prairie. With my guidance, training and assistance students collected, identified, pressed, and dried more that 600 vascular plant specimens representing at least 50 families. These specimens are stored in the Mendocino College Herbarium which I established in 1998.