Research in the Eppley Lab
The functional role of moss in structuring biotic interactions, and terrestrialization of Antarctica: Despite the harsh abiotic conditions, one hundred and eleven moss species occur in Antarctica (compared with only two flowering plants). As the continent becomes warmer and wetter mosses are colonizing newly exposed ground, and are predicted to become even more dominant. Recent research has focused on the importance of mosses in Arctic tundra systems, where their role in the global carbon cycle is a matter of immediate concern. These studies have revealed the surprising importance of bryophytes as ecosystem engineers, with roles in regulating nutrient cycling, controlling trophic structure, and amelioration of abiotic conditions. In contrast to Arctic systems, we know relatively little about the role of Antarctic mosses in organizing communities or shaping ecosystem processes, and less still on how individual moss species and genotypes influence Antarctic ecology. With this in mind, we propose to test hypotheses concerning the effects of warming on how Antarctic mosses structure terrestrial ecosystems. We will use Open Top Chamber passive warming experiments, which have been installed for five years by our Chilean collaborator on King George and Livingston Islands, and we will concentrate on how warming impacts bryophyte productivity, sexual systems, and secondary chemistries, and how these changes affect community processes. We propose to pursue three integrated research hypotheses: 1) Warming will alter moss species composition, moss sex ratio, and differentially impact moss productivity and reproductive success in Antarctica; 2) Warming will impact the production of moss secondary compounds, influencing the dynamics of biotic interactions and biosphere-atmosphere exchange in terrestrial Antarctica; and 3) Warming will alter moss-microbe interactions, resulting in alterations to the moss food web and community dynamics in terrestrial Antarctica. These data will be the first comprehensive measures of how Antarctic mosses engineer their environment and thereby drive terrestrial responses to global warming.
Sex in extreme environments: testing the ecological and physiological contraints to sexual reproduction in bryophytes: Producing offspring by sexual reproduction is potentially genetically and physically risky, yet most Eukaryotes reproduce primarily via sexual rather than asexual reproduction. Many studies have found positive correlations between environmental stress and sexual reproduction, suggesting that under stressful conditions sex has an adaptive function. However, the correlation between sex and stress has not been found to extend to extreme environments, although there has been only a few studies in this area. Understanding how sex functions in extreme environments has striking implications for the evolution of sex, which may have evolved in organisms in extreme environments, and the maintenance of sex in organisms that inhabit extreme environments today. It has been suggested that when environmental stress is extremely high only a few genotypes are adaptive; if this is the case, then recombination would not be an adaptive strategy.
To test whether the positive correlation between genetic variation, sexual reproduction, and environmental stress occurs in the majority of environments except extreme environments, we are using bryophytes around geothermally heated hot springs as a model system. Preliminary data for this project were collected around hot springs on New Zealand’s North Island, and we are currently developing this project at Lassen Volcanic National Park, California. We plan to use a series of greenhouse experiments to determine the effects of environment and genetics in sexual versus asexual reproduction in extreme environments and to develop microsatellite markers for a handfull of bryophyte species to estimate the relationship between sexual reproduction and environmental stress.
We are growing several bryophyte species in the greenhouse that were collected from around fumeroles at Boiling Spring Lake and Devil's Kitchen at Lassen Volcanic National Park to determine the heat tolerance of individual species. Moss plants were found green and growing (see photo below) at soil surface temperatures above 58ºC, and soil temperatures at 10 cm of 77ºC.
PSU student, Camille Graves, collecting data on
moss communities at Lassen Volcanic National Park
Moss community around a fumarole
Boiling Spring Lake, Lassen
Moss mating systems: Although land plants evolved with mating systems that relied on motile sperm swimming across stressful environments for fertilization, this reliance has often been considered the weak link in the life-history of non-vascular plants. New research, however, suggests that moss sperm may actually move an order of magnitude farther than previously believed and possibly be dispersed by microarthropods, building on much earlier work suggesting arthropods as sperm vectors. We are using the emerging model system Ceratodon purpureus to comprehensively examine male mating success in light of recent findings.
Spatial segregation of the sexes in Distichlis spicata: Understanding the evolution of ecological niches is a focal area of evolutionary ecology. This project examines the genetic, physiological, and ecological factors that allow male and female plants in the wetland grass species Distichlis spicata to have evolved and maintain different ecological niches. Despite the fact that sex ratio theory suggests that such a spatial structure should be highly disadvantageous in a sessile organism because it reduces mating success, patterns of intraspecific niche dimorphism, also known as spatial segregation of the sexes, are quite common in dioecious plants. Currently, we are using greenhouse experiments and plan to set up long-term reciprocal transplant experiments in the field to test evolutionary hypotheses and physiological mechanisms that have been proposed to explain spatial segregation of the sexes in D. spicata.
More information on spatial segregation of the sexes in D. spicata can be found on our project website: SSS inDistichlis spicata.
Students planting D. spicata seedlings at Tomales Bay, CA
The effects of Hedra helix management strategies in Portland, Oregon’s urban ecosystems: The aim of this project is to test the effects of management strategies for an invasive plant, Hedra helix (English Ivy), and overall habitat disturbance on native biodiversity in Portland, Oregon’s urban environment. The project is being conducted by undergraduates at Portland State University in collaboration with The No Ivy League, Forest Park, Portland and the City of Portland’s Parks and Recreation Department. The No Ivy League is a non-profit organization that has been removing H. helix from Portland parks for many years and has reliable management records that can be used for this study. Long term plots have been established in Himes Park to assess the effects of ivy management strategies on understory vegetation.
Dr. Angélica Casanova-Katny, Facultad de Química y Biología, Universidad de Santiago
Dr. Linley Jesson, University of Victoria, Wellington; University of New Brunswick
Dr. Phil Garnock-Jones, University of Victoria, Wellington
Dr. Nicholas McLetchie, University of Kentucky
Dr. John Pannell, Universite de Lausanne
Dr. Todd Rosenstiel, Portland State University
Dr. Lloyd Stark, University of Navada, Las Vegas
Phil Taylor, University of Victoria, Wellington
Dr. Olga Tsyusko, University of Georgia, Savannah River Ecology Laboratory
Dr. Gustavo E. Zúñiga, Department of Plant Physiology and Biotechnology, University of Santiago