Jacob
Tennessen
PhD in Zoology, OSU 2009
B.S. in Biological Sciences, Cornell University 2002
I study evolutionary genetics, primarily adaptive molecular evolution. Much of my work has focused on herpetofauna, but I'm interested in all taxa.
Research projects from my undergraduate days have included a mitochondrial phylogeography of the striped plateau lizard, and a microsatellite-based paternity analysis of spotted salamander larvae resulting from field experiments to determine how male mating order affects reproductive success.
My dissertation work is on the evolution of animal antimicrobial peptides, which are produced by numerous taxa to kill bacteria and other pathogens. They frequently evolve via positive natural selection, which is unusual as most "normal" genes evolve neutrally. I have studied evolutionary patterns in antimicrobial peptide gene sequences from frogs and fishes, to see whether positive selection drove their evolution, how selection and mutation cause different regions of the genes to evolve at different rates, and whether different regions of the genes evolve in a coordinated fashion with each other. Using both functional and sequence data on antimicrobial peptides from many different animals, I am studying the evolutionary conditions associated with positive selection, and how adaptive changes affect a peptide's ability to kill different microbes. Finally, I am sequencing antimicrobial peptide genes in the northern leopard frog (Rana pipiens) and related species to look for evidence of adaptive evolution, count the number of duplicated loci, and assess intraspecies allelic diversity.
The fundamental process of adaptive evolution is still poorly understood at the molecular level where it actually happens, and antimicrobial peptides are ideal for research in this area. For example, hypotheses about how selection and gene flow interact to produce microevolutionary patterns can be tested with genes that regularly evolve adaptively. Beyond just building evolutionary theory, understanding the genetic basis for the evolution of disease resistance is important for the conservation of biodiversity, because emerging infectious diseases threaten many species, especially amphibians. Furthermore, antimicrobial peptides with different fitness effects are likely to be functionally divergent, which could lead to different biotechnological applications.
Make your own discoveries in molecular evolution at home!
Publications:
Tennessen JA, Blouin MS (2008) Balancing selection at a frog antimicrobial peptide locus: fluctuating immune effector alleles? Molecular Biology and Evolution 25:2669–2680
Tennessen JA (2008) Positive selection drives a correlation between non-synonymous/synonymous divergence and functional divergence. Bioinformatics 24:1421-1425
Tennessen JA, Zamudio KR (2008) Genetic differentiation among mountain island populations of the striped plateau lizard, Sceloporus virgatus (Squamata: Phrynosomatidae). Copeia 2008:558-564
Miranda RR, Tennessen JA, Blouin MS, Rabelo EM (2008) Mitochondrial DNA variation of the dog hookworm Ancylostoma caninum in Brazilian populations. Veterinary Parasitology 151:61-67
Tennessen JA, Blouin MS (2007) Selection for antimicrobial peptide diversity in frogs leads to gene duplication and low allelic variation. Journal of Molecular Evolution 65:605-615
Tennessen JA (2005) Molecular evolution of animal antimicrobial peptides: widespread moderate positive selection. Journal of Evolutionary Biology 18:1387-1394
Tennessen JA (2005) Enhanced synonymous site divergence in positively selected vertebrate antimicrobial peptide genes. Journal of Molecular Evolution 61:445-455
Tennessen JA, Zamudio KR (2003) Early-male reproductive advantage, multiple paternity, and sperm storage in an amphibian aggregate breeder. Molecular Ecology 12:1567-1576
Contact info:
Jacob Tennessen Zoology Dept. 3029 Cordley Hall Oregon State University Corvallis, OR 97330 (541)737-4360 E-mail: tennessj AT science DOT oregonstate DOT edu
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Last updated March 7, 2009