Deborah
A. Roach
Associate Professor
Recipient of the 2006 Cavalier Distinguished
Teaching Award
Recipient of the 2006 Cavalier Distinguished Teaching Award
Ph.D. Duke
University
(434) 982-4858
A note to prospective
graduate students:
I am currently accepting new
graduate students interested in topics related to plant ecology, life history
evolution, or evolutionary ecology. The
faculty and graduate students within the Ecology and Evolution Program at UVA
are a very lively and interactive group and one of our major strengths is in
plant evolutionary ecology. Students in my lab have the opportunity to design
projects either tangentially related to my current projects or using a study
system of their own choice. Please contact me by email if you are interested in
applying.
CURRENT RESEARCH
PROJECTS:
One major research project in my lab is a long-term investigation into the
patterns of mortality and aging in a natural plant population. Using a large
experimental field population of Plantago lanceolata we have been able
to demonstrate that mortality patterns depend not only on abiotic factors,
such as temperature and cumulative precipitation, but also on biotic factors
such as reproduction and size. The preliminary results of these studies suggest
that this species that can continue to grow after reproductive maturity may,
at least for some period of the adult stage, be able to escape the process
of aging. These studies have focused on measuring aging as a change in the
risk of mortality, and so far there is no evidence for an increasing risk
of dying for P. lanceolata as individuals get older. We are continuing
these observations to later ages and we are now also incorporating measures
of physiological functioning. Can this species that, so far, appears to be
able to escape demographic aging also escape physiological aging? Do these
patterns continue to extremely old age? If so, what unique features of the
biology of this plant species allow it to escape this deleterious phenomenon?
Temporal variation in traits
in a natural population.
We currently have an experiment, with Plantago lanceolata, that
uses multiple cohorts, with the same genetic composition, to address questions
about temporal variation in morphological, physiological, and life history
traits. In one project we showed that contrary to the assumption of
many demographic models, successive life stages are not independent. In other
words, the reproductive output of individuals as adults, for example, will
vary within a population depending on conditions experienced by those individuals
when they were younger. As a consequence, if different cohorts experience
different ecological and selective histories, then this may result in variation
in patterns of mortality and reproduction that may be due not only to age
but also to the history of individuals within the population. These historical
factors must be taken into consideration if we want to understand the dynamics
of reproduction and mortality within a population (Roach
2003).
An increasing incidence of disease in older
individuals is often considered to be a manifestation of aging. In this context
we were interested in measuring the temporal variation in the frequency of
a pathogen, Fusarium moniliforme, which infects Plantago. The
results of this study showed between year variation in infection frequency
and a decrease in frequency with increasing longevity (Dudycha
and Roach 2002). These results provide further evidence that P. lanceolata
may be able to escape the aging process.
Temporal variation may be important not only
across years but even within a single growing season. In a field experiment
with P. lanceolata we evaluated the consequences of temporal variation
in the time of flowering and fruiting within a growing season on both the
total seed set for a maternal parent and on the quality of the seed produced
(Lacey, Roach
et al. 2003). We found that individuals that began flowering earlier produced
seed for a longer time and produced more seed, but later-maturing seeds were
significantly heavier and germinated more rapidly. In other words, there are
cross-generational tradeoffs between parental and offspring components of
parental fitness that may influence the evolution of reproductive phenology.
Spatial variation in a natural population. Spatial location is critical
for the ecology of plants because plants cannot move. In a large experiment
with Plantago lanceolata, we planted individuals in the field in a
regular grid design. This allowed us to assign a coordinate to every individual
and thus to identify its exact location relative to other plants in the population.
We are now asking questions about the scale of micro-environmental change
across our experimental field. For example, are the locations in the field
that are favorable for juvenile growth also favorable for adult reproduction?
Or, are different spatial locations better for traits at different life
stages? We also know the exact location of the parents that we dug up from
this field before we transplanted them to the greenhouse to make the seeds
for these experimental plants. With this information we are now asking questions
such as: Do offspring located relatively close to the site from where one
of their parents was located perform better than their siblings located farther
from the parental site? In other words, is there any evidence for local adaptation
in this population of P. lanceolata?
UNDERGRADUATES IN THE
LAB:
There are opportunities in my lab for both paid undergraduate research assistant
positions and for independent study for academic credit. Paid research assistants
gain experience working on my projects on the field, greenhouse, and in the
lab. In addition to part-time positions in the semester, I hire several full-time
students for the summer field season. I also have had several recent graduates
working full-time in my lab to gain research experience before applying to
graduate school.
