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Via Lab
Department of Biology and Department of Entomology Phone: 301-405-8942 Via faculty page |
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Contents
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Via Lab and friends
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What IS ecological genetics?
In most biology curricula, ecology, evolution and genetics are taught as separate courses that may appear to have little overlap. However, ecology and genetics together form the mechanisms of evolutionary change: Ecological interactions or organisms with the biotic and abiotic environment are the context of natural selection -- they determine the phenotype that does the best in a given situation. The ecological structure of populations (size, degree of fragmentation, etc.) also determines the potential for genetic drift (non-adaptive genetic change in populations). Genetic variability within populations for phenotypic characters that are ecologically important determines the speed and directionality of the response of populations to the selection resulting from ecological interactions . Thus, to understand the potential for (and constraints on) evolution in contemporary populations, one must consider both ecological and genetic issues. Further context is provided by placing analysis of contemporary populations into a phylogenetic context (either through phylogeographic analyses within species or through broader systematic analysis of sets of taxa).
Ecological genetics is thus a point of view in which awareness of variability among organisms is involved in the study of all kinds of ecological interactions, both biotic and abiotic. In this outlook, key ecological parameters (population growth rate, competitive ability, attack rates of predators, etc) are not considered fixed properties of populations or species, but are allowed to evolve in an ongoing feedback between ecology and genetics. This outlook underlies everything we do in the Via Lab.
Descriptions of Current Research Projects
1. Genetic architecture of specialization
and reproductive isolation in pea aphids on two hosts.
From my previous work, we know (1) that sympatric populations
of pea aphids on two hosts (alfalfa and red clover) are highly genetically
differentiated and locally adapted,
(2) that these populations are significantly reproductively isolated from one
another, despite a lack of physical
barriers to gene flow, (3) that much of the reproductive isolation is due to
strong genetically based host plant
discrimination, and (4) that an ecological disadvantage of migrants and hybrids
in the parental environments is
also responsible for some reproductive isolation.
We are currently using techniques of Quantitative Trait Locus (QTL) mapping to attempt to answer several crucial questions in the evolution of specialization and reproductive isolation of populations in sympatry: (1) Does performance attained on the two hosts map to the same segment of chromosome? (2) Does host choice behavior map to the same location as performance? (3) How many genes are involved in specialization and host choice, and what is the range of gene action of alleles at these loci? Remarkably little is known about the genetics of speciation and reproductive isolation outside Drosophila. We are hopeful that this study will provide new insights into the process of speciation.
We are currently doing the phenotyping of F2 progeny of a cross between an alfalfa and clover specialist in the Via Lab. Genotyping and linkage mapping is being done using AFLPs in the lab of David Hawthorne, Department of Entomology.
2. Mechanism of resource specialization in pea aphids: specialized feeding behavior. (In collaboration with Dr. Marina Caillaud , Cornell University and INRA, France). We are studying the detailed feeding behavior of specialized aphids and their F2 progeny on the two hosts. Marina uses a technique to study aphid feeding in which aphids are attached to a very fine gold wire and then a small DC current is passed through them. When they probe into the plant, a circuit is completed, and the waveforms visualized reveal where in the plant the aphid's stylets are located. Using this method, we can determine the time an aphid spends searching for phloem, how long it takes to find the phloem, and for how long it feeds. We are using these methods in conjunction with the QTL analysis described above to evaluate the genetic architecture of a highly specialized feeding behavior.
3. Phylogeography of pea aphids on two hosts. Pea aphids on alfalfa and clover are locally adapted in New York, Iowa and Sweden (work of Jonas Sandstrom). Did the host-associated races diverge once in Europe, before they were introduced to North America, or have they evolved specialization to the two hosts multiple times independently? In collaboration with David Hawthorne, we are using MtDNA analyses of collections from across Europe and North America to answer this question.
4. Ecological genetics and the prospects
for coevolution of insects and their parasitoids and pathogens.
How can coevolution be studied in action? How
much genetic variation is there in resistance and virulence of the interacting
species? How strongly do species
act as agents of selection on one another?? The genetics of interactions
between aphids and their natural enemies
has, so far, largely been the province of graduate students in the Via Lab.
Former graduate student Heather Henter
showed that single fields of aphids and wasps both harbor amazing amounts of
genetic variation in resistance (aphids)
and virulence (wasps). Read more about this in Evolution, 1995. Ruth Hufbauer
(current student) tested whether
the host-associated races of aphids might be different environments for the
wasp parasitoids and whether wasps
might be locally adapted. Kirsten Hural studied the genetics of the interaction
between pea aphids and their fungal
pathogen, and, again, documented surprising amounts of genetic variation among
aphid genotypes in resistance to
the fungus. Clearly, a typological view of species interactions will not be
adequate to produce a deep understanding
of how species affect one another.
Current Personnel in the Via Lab
Graduate Students: Ruth Hufbauer (Cornell University, rah4@cornell.edu ): ecological genetics of aphid-parasitoid interactions
Technicians: Carrie Wicklund (BS, Harvey Mudd College, 1998) Christy Olson (BS, University of Minnesota, 1998)
Undergrads: Seyad Zeyad, Barry Hammen, John Arigo, Evelyn Yates, Meera Srinivasan
Postdoctoral Associate: Marina Caillaud (Cornell University and INRA, France, cmc27@cornell.edu )
Former Personnel:
Graduate Students and position upon graduation:
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Alison Shaw (M.S. 1993, left science) Heather Henter (Ph.D, 1995, Ecological
genetics of aphid-
parasitoid interactions; Asst. Prof., Cal. State LA)
Saskya van Nouhuys (Ph.D, 1998, Postdoc, Ilkka Hanski, University of Helsinki)
Kirsten Hural (Ph.D. 1998, Instructor, Dickinson College)
Postdocs:
Dianna Padilla (1988-89, Asst. Prof., University of Wisconsin)
Jeff Conner (1989-92, Asst. Prof., University of Illinois)
Technicians and position upon leaving:
Jordan West (1986-88, graduate student, Ecology and Systematics, Cornell
University)
Jill Rogers (1991-93, graduate student, Biochemistry, Berkeley)
Donna Conlon (1993-95, went into science education)
Jan Schlesinger (1995-96, technician for Dr. Tom Eisner, Cornell)
Amy Bouck (1995-98, graduate student, Genetics, University of Georgia)
Stasia Skillman (1996-98, graduate student TBA)
Undergraduates:
Rebecca Zufall (1995-97, graduate student, Duke University)
David Gilley (1995-97, graduate student, Cornell University)
Spencer Hall (1995-97, graduate student, University of Chicago)
For prospective grad students: graduate
student life in the Via Lab
An extremely important part of graduate school is the discovery of questions
worth asking. Thus, I don't encourage
my students to work on my projects. However, there are a number of ancillary
issues to the ongoing pea aphid work
that would be great projects, and I would be happy for grad students to pick up
on these and develop them. When
choosing a topic, I encourage students to focus on some issue in ecological
genetics and evolution. My students
have mostly worked on insects, but there is no reason why work on plants is not
possible.
We try to have regular lab meetings in which we discuss ongoing and planned
work, or in which we read current papers
of interest to the group. My hope is that students will read and think broadly
when considering their projects,
and lab meetings are a good place to kick around ideas. The ideal is to have a
range of student expertise in the
lab, so that the more advanced students can help the newer ones. Since I
arrived at Maryland only a year ago, I
don't currently have this range, but this will hopefully build in the next few
years.
My students may enter graduate school at Maryland through either the Biology
Department or the Department of Entomology.
