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Jessica Wright
- Conservation Biology
The Wright lab is focused on a number of projects with an overall goal
to gain understanding of major issues in conservation biology through
the use of molecular and quantitative genetic techniques.
Population Fragmentation
Habitat fragmentation is of major concern to conservation biology, and
is considered one of the four threats by the Forest Service. To understand
the long-term dynamics of human-caused habitat fragmentation, the Wright
lab studies the conservation genetics of naturally fragmented populations
using Serpentine soils in California as a model system. Serpentine soils
are a particularly nasty place for plants to grow. They contain high levels
of heavy metals, are low in nutrients and have a low Calcium: Magnesium
(Ca:Mg) ratio, which leads to an odd ionic balance in the soils. Rather
than being barren wastelands, many plants are adapted to grow on serpentine
soils. Serpentine and non-serpentine soils are a naturally fragmented
habitat, with serpentine and non-serpentine soils occurring in close proximity.
The Wright lab focuses on species that grow both on and off of serpentine
soils. Listed below are some of our current projects.
Adaptation to serpentine soils in Collinsia sparsiflora
We have worked extensively with a native annual plant, Collinsia sparsiflora,
which grows on and off of serpentine soils. We have demonstrated local
adaptation to serpentine soils in this species through 2 reciprocal transplant
experiments using 3 serpentine and 3 non-serpentine sites. The results
of these studies clearly show that plants grow best on their home soil
type- in both directions (see graph below). That is, plants from serpentine
habitats grow best in serpentine habitats, and plants from non-serpentine
habitats do best in non-serpentine habitats. This result is fairly remarkable
in that the distance between study sites is less that 1 km, with the closest
two sites being 75 meters apart. Obviously, these results have practical
implications for management of serpentine areas. For example, restoration
efforts need to focus on collecting locally adapted seeds, as using non-serpentine
seed-sources in serpentine areas may lead to a failure in restoration
efforts.
This finding of local adaptation to serpentine and non-serpentine soils
has lead to a series of other research directions in both the field and
the lab. We are using microsatellite, AFLP and SNP markers to study population
differentiation and gene flow between and within populations growing on
and off of serpentine soils. These results are showing strong evidence
for gene flow between the populations, with little differentiation between
serpentine and non-serpentine populations. This result is very surprising,
given the result of the reciprocal transplant experiment, illustrating
the importance of combing field and molecular results.
In collaboration with K. Davies, J. McKay, A. McCall and J. Lau, we have
conducted a larger field experiment, where we used a model created by
K. Davies (University of Colorado) to predict the performance of C.
sparsiflora in well-characterized habitats. We planted seeds into
a range of habitats, and determined that the predictions of the model
were accurate, and that we had successfully described the niche of C.
sparsiflora. Moreover, further analysis revealed that the serpentine
ecotype has a different niche than the non-serpentine ecotype, as we were
not able to predict the performance of non-serpentine plants. Studies
such as these are important for understanding the distribution of species,
and will play a critical role in predicting and understanding the future
impacts of global climate change.
Tolerance of serpentine soils in ponderosa pine
We are investigating a reciprocal transplant experiment established in
1970 by J. Jenkinson, a PSW scientist. Trees were planted reciprocally
between serpentine and non-serpentine sites in El Dorado County. Our results
show that even in a long-lived, wind-pollinated species, growing in very
different habitats only 1.4 km apart, the results are similar to those
obtained for C. sparsiflora- local adaptation to both serpentine
and non-serpentine soil habitats. We have also collected allozyme data
from the surviving trees, and have archived DNA from each surviving tree
in the plantations. We are currently focused on the development of markers
to use in this experiment. This study is potentially very useful as most
P. ponderosa seed zones are based on climate and altitude data,
and do not consider soil characteristics.
Impacts on Native Species by Invasive Species
Invasive species come in all forms- plants, animals, pathogens. They each
have an impact on the ecosystem they invade. The Wright lab is part of
a collaborative effort, coordinated by Richard Sniezko, funded through
the PSW Sudden Oak Death Project, as well as the Midpeninsula Regional
Open Space District. A diverse group of scientists are conducting 4 concurrent
experiments on a set of maternal Tanoak trees, collected from populations
across California and Oregon. In the spring of 2006, 100 acorns were collected
from approximately 30 trees in 5 populations. These acorn collections
were then divided into 3 sets for use in a series of collaborative experiments.
Two experiments, coordinated by Mateo Garbelotto and Katy Hayden (UC Berkeley)
focus on resistance to the introduced pathogen, sudden oak death (SOD).
A third experiment, run by Richard Dodd (UC Berkeley), examines molecular
genetic variation using tissue from the maternal trees. The Wright lab
is conducting the fourth experiment, which looks at quantitative genetic
variation in these populations. Together these data will provide an understanding
of the relationship between disease resistance, molecular genetic variation
and quantitative genetic variation. As climate change continues, more
and more species will be able to invade new areas where they previously
could not occur. Understanding the relationship between genetic variation
in native populations, and their resistance to invasive diseases will
be key to managing future outbreaks of new invasive pests.
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