Research Interests

C. vittatus under UV light.

My current research revolves around the population genetics of the bark scorpion Centruroides vittatus. Populations of this scorpion encompass a large geographic range that includes southern Colorado, eastern New Mexico, several of the states in northern Mexico, Texas, western Louisiana, western Arkansas, southern Missouri, Oklahoma, and much of Kansas.

This is the range of C. vittatus in the midwest and C.hentzi in the east. Shelley, R.M. and W.D. Sissom. 1985. Distributions of the scorpions Centruroides vittatus (Say) and Centruroides hentzi (Banks) in the United States and Mexico (Scorpiones, Buthidae). JOA 23:100-110.

My lab is working to develop genetic markers to conduct an analysis that will show the phylogeographic relationship among populations of this scorpion. We are investigating RAPDs (Random Polymorphic DNA), DNA sequences, AFLP's (Amplified Fragment Length Polymorphisms), and microsatellities (with Dr. Douglas Rhoads, UA-F) for this project.

Most recently, I have become interested in the differentiation of venom toxin genes among C. vittatus populations and how these toxin genes have evolved in this less toxic sister species to C. exilicauda. To investigate these genes, I plan to obtain genetic markers (microsatellities and SNP's) that will allow allow a comparison of genetic diversity among scorpion populations and diversification of toxin genes. Here I would be interested in if genetic divergence among populations can be correlated with toxin gene diversification. In addition, I plan to compare toxin genes in C. vittatus to homologous genes in C exilicauda to determine if changes have occurred in protein coding sequences.

Arkansas populations of this scorpion show reduced densities as compared to western Texas populations [AR populations: 0.818 individuals/100m2 (2000 estimate), 0.456 individuals/m2 (2003 estimate); Texas estimate: 7.36 individuals/100m2]. Arkansas scorpions were not active on the surface during December, January, February, and March but Texas scorpions were active all year. Arkansas scorpions exhibited lower biomass than Texas scorpions 0.133 kg/ha (2001) and 0.111 kg/ha (2003); TX- 0.31 kg/ha. Average female mass in Arkansas was 0.49 gm; male mass was 0.41 gms. Texas scorpions exhibited similar male mass (0.419 gms) but markedly larger female mass (0.765 gm). Lastly, Arkansas populations exhibited high cannibalism rates comparable to the sand scorpion (9.1% versus 9.52%, AR striped scorpions). These findings suggest Arkansas scorpions exhibit food stress. This stress may result from a recent expansion into eastern areas from western regions during a warming trend approximately 8,000 to 4,000 years before present. This scorpion maybe exhibiting incomplete adaptations to recent climatic changes in this region. The Texas estimates stem from Brown et al. 2002.

I plan to use this scorpion to show Arkansas' unique biogeographic history. The Ozarks and Ouachita mountains appear to possess a unique biogeographic history because many habitats show plants and animals representative of eastern forms but may also show species more common in the western United States.

Other projects with students at Tech include Mussel (L. hydiana) DNA sequencing analysis, ladybeetle RAPD analysis and the morphological analysis of C. vittatus populations.

Curriculum Vitae

PROFESSIONAL INFORMATION
Academic Degrees:

   1993 Ph.D.            Department of Biology,	Vanderbilt University, Nashville, TN 37235

   1985 B.A.             Hendrix College, Conway, AR 72032

Professional experience:

2003-present

Associate Professor, Department of Biological Sciences
Arkansas Tech University

1998-2003

Assistant Professor, Department of Biological Sciences
Arkansas Tech University

Adjunct Assistant Professor, Department of Biology
Northeast Louisiana University

Assistant Professor (Graduate Faculty), Department of Biology
Northeast Louisiana University

Post-doctorate, Division of Hematology
Vanderbilt University Medical School

Teaching Assistant
Vanderbilt University

Grant Awards:
2006 (J Stoeckel and T Yamashita) Status and genetics of the stargazing darter in Arkansas. Arkansas Game and Fish Commission. $25,000.00

2005 (T Yamashita) Molecular biology of the striped scorpion ( Centruroides vittatus): toxin gene analysis. ATU Sponsored Programs. $3,300.00

2004 (T Yamashita and DR Rhoads) Identification and characterization of microsatellite loci, SNPs, and toxin genes for genetic analysis of a medically important scorpion species. Arkansas BRIN. $16,985.00

2003 (T Yamashita) Genetic Analysis of Scorpion Toxin Genes. Faculty research grant, ATU Undergraduate Research Office. $2,500.00

2003 (T Yamashita) BRIN Equipment Supplement to Summer BRIN award. Arkansas BRIN. $25,350.00

2003 (T Yamashita and DR Rhoads) Identification and characterization of microsatellite loci for genetic analysis of a medically important scorpion species. Arkansas BRIN. $15,590.00

2001 (T Yamashita and Joe Stoeckel) Employing genetic markers to reveal taxa in a morphologically similar mussel complex. Arkansas Tech University Undergraduate Research Office $3750.00

1999 (T Yamashita) An evaluation for investigation of genetic markers for population analysis. Center for Energy, Natural resources and Environmental Studies. $7,732.00

1998 (R Buchholz and T Yamashita) Investigation of the parasitological and genetic mechanisms shaping sexually selected characters in the wild turkey in Louisiana. Louisiana Education Quality Support Fund (LeQSF). $70,000.00

1998 (A Findley, S Hecht, T Yamashita, and M Taylor) Teaching Molecular Biology in the Laboratory. NLU developmental Grants Program. $10,000.00

1996 (T Yamashita) Improving the undergraduate genetics laboratory. NLU Teaching and Learning Resource Center Grant Award. $2,855.00

1995 (T Yamashita and K Tolson) PCR detection of Mycobacterium leprae in armadillo lymphatic tissue. NLU Faculty Research Award. $3,510.00

1994 (T Yamashita) Population genetics analysis of cottonmouth populations in the upper Saline River. NLU Faculty Research Award. $3,000.00

1988 California Academy of Sciences: Exline-Frizzell Fund for Arachnological Research. $500.00

Publications:
Yamashita, T. 2004. Surface activity, biomass, and phenology of the striped scorpion, Centruroides vittatus in Arkansas. Euscorpius -Occasional Publications in Scorpiology 17: 25-33.

J Lewter, T Yamashita, and AL Szalanski. 2003. DNA sequence analysis of the freshwater mussel, Lampsilis hydiana (Bivalvia: Unionidae), in select Ozark and Ouachita mountain streams of Arkansas. J. of the Arkansas Academy of Science 57: 216-220.

Yamashita, T. and V. Fet. 2000. Molecular approaches to Biogeography. In G. Polis and P. Brownell (Eds) Scorpion Biology. Oxford University Press.

Bondurant, M.C., T. Yamashita, K. Muta, S.B. Krantz, and M.J. Koury. 1996. c-myc expression affects proliferation but not terminal differentiation or survival of explanted erythoid progenitor cells. Journal of Cellular Physiology 168: 255-263.

Yamashita, T and G.A. Polis. 1995. A Geographic Analysis of Scorpion Populations on Habitat Islands. Heredity 75 (5): 495-505.

Yamashita, T. and G.A. Polis. 1995. A test of the central-marginal model using sand scorpion populations (Paruroctonus mesaensis, Vaejovidae). Journal of Arachnology 23: 60-64.

Polis, G.A. and T. Yamashita 1990. The ecological importance of predaceous arthropods in desert communities. In G. Polis (Ed) The Ecology of Desert Communities. Univ. of Arizona Press, Tucson, AZ

Abstracts:
T Yamashita, Maria Longing, and Nick Pridgin, Phylogeography of the striped scorpion, Centruroides vittatus in the southwestern United States. American Arachnological Society Meeting, June 2005.

T Yamashita and DR Rhoads. Identification and characterization of microsatellite loci , SNPÕs, and toxin genes for genetic analysis of a medically important scorpion species, Centruroides vittatus. Arkansas BRIN Research Mentoring Program-Research Day. July 2004

T Yamashita. Surface activity, biomass, and phenology of the striped scorpion, Centruroides vittatus in Arkansas. American Arachnological Society Meeting, June 2004.

T Yamashita and DR Rhoads. Microsatellite identification in a medically important scorpion species, Centruroides vittatus. Arkansas BRIN Research Mentoring Program-Research Day. July 2003

T Yamashita. Phylogeography of the striped scorpion, Centruroides vittatus. Arkansas Academy of Science, April 2003

J Lewter, T Yamashita, and AL Szalanski. DNA sequence analysis of the freshwater mussel, Lampsilis hydiana (Bivalvia: Unionidae), in select Ozark and Ouachita mountain streams of Arkansas. Arkansas Academy of Science, April 2003

Yamashita, T and D. Hodgson. A screening of two scorpion populations, Centruroides vittatus (Say) for random amplified polymorphic DNA markers. American Arachnological Society Meeting, July 2000.

Yamashita, T and J. Qin PCR detection of Mycobacterium leprae in the armadillo, Dasypus novemcinctus. Association of Southeastern Biologists meeting, April 1998.

Williams, R and T Yamashita. Population genetics of an introduced ladybird beetle (Harmonia axyridis) Louisiana Academy of Sciences meeting, February 1998.

Bondurant, M., K. Muta, T. Yamashita, L. Kelley, S.B. Krantz, and M. Koury 1993. Erythropoietin stimulates expression of c-myc without stimulating cell division in explanted mouse and human erythroblasts. Abstract submitted for the American Society of Hematology meeting, December 1993.

Awards and Honors:
Alpha Lambda Delta -the freshman honor society- Favorite professor (Spring 1994)
Baptist Student Union- Favorite professor (Spring 1995)

Teaching experience and interests:
Courses taught:
Lecture: Introduction to Zoology, Genetics, Principles of Biology, Non-majors Biology (Living World, Man and the Living World, Introduction to Biological Sciences), Population genetics, and Evolution
Laboratories: Genetics, General Biology, General Zoology, Introduction to Biological Sciences, and Cell Biology.
University Activities:
ATU Convocations and Programs Committee: 1999-2000
ATU Whos Who Committee: 1998
Adjunct Assistant Professor of Biology at NLU 1998

Departmental Committee Duties:
Biological Science Lab Revision Committee 1999
Arkansas Academy of Sciences Local Organizational Committee 1999

Other Departmental Activities:

Advisor ATU TriBeta Chapter

NLU:
Coordinator for an undergraduate honors project: Population genetics of an introduced ladybird beetle (Harmonia axyridis). This work was presented at the 1998 Southern Regional Honors Conference in Savannah, GA. February 1998.

Attended Workshops:
Summer Institute in Statistical Genetics at NC State University. Summer 1999
LaCEPT (Louisiana Collaborative for Excellence in the Preparation of Teachers): Science reform and methodologies at the university level. 1995

Membership in Professional Organizations:
Society for the study of Evolution, American Arachnological Society

Community Activities:
Arkansas Canoe Club Rendezvous Chair 1999/2000
Assistant Scoutmaster Boy Scout Troop 400 (Russellville, AR) 1999-2000
Assistant Scoutmaster Boy Scout Troop 28 (Monroe, LA) 1995-1998
First Assistant Scoutmaster BSA Jamboree Troop 1823 (Monroe, LA) July-August 1998
Ouachita Valley Council Advancement Committee Chair (Monroe, LA) 1998
Instructor for Arkansas Canoe Club's canoe school: 1997-2002
President- Piney Creeks Chapter, Arkansas Canoe Club 1999-2001

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