Faculty Research

Check out a recent interview with Dr. Hendrixson on native U.S. Tarantulas.

As human populations continue to grow without limits, our planet’s most precious resource – biological diversity – is disappearing at an unprecedented rate. The consequences of this human-induced mass extinction are not yet well understood, but most scientists agree that the results will be devastating. Continued loss of biodiversity cannot be sustained indefinitely – that is, of course, unless humanity braces itself to experience the same fate. However, before we can begin to comprehend the consequences of extinction or devise conservation strategies, we must know what organisms exist in the biosphere. Many exciting species remain unclassified and millions more await discovery! At its core, my research program aims to identify genetic and species-level diversity in spiders, but ultimately seeks to address broader-scale questions with regards to their evolution, biogeography, and conservation. Students in my laboratory have unique opportunities to synthesize data collected through two seemingly dissimilar areas of biology (field-based and molecular lab-based) to tackle difficult questions that likely cannot be answered by either discipline in itself.

I am presently working on the tarantula genus Aphonopelma. Most species are inadequately defined and a substantial number of undocumented species (i.e., a species that has not been formerly named) exist, necessitating this research. A handful of students have traveled with me to California, Nevada, Utah, Arizona, New Mexico, Colorado, Kansas, Oklahoma, and Texas to assist collecting tarantulas so we can better assess the diversity of these spiders in the United States. A few novel spiders were discovered during the course of these field expeditions and future collecting trips into mainland Mexico and Costa Rica will surely uncover many more. In the molecular laboratory, students have learned how to extract DNA from spider tissues, perform PCR (polymerase chain reaction) to amplify genes of interest, and set-up DNA sequencing reactions. In the future, students will become familiar with phylogenetic and GIS (geographic information system) analyses. Generous financial support for my research program has been provided by the National Science Foundation and American Tarantula Society.

 
 

One of the hallmarks of cancer cells is loss of control of cell division, and understanding the regulators of cell division is essential to understanding the nature of cancer. The main focus of work in my laboratory is to understand the molecular and genetic mechanisms that control cell division. Since these mechanisms are highly evolutionarily conserved, cell division can be studied in lower organisms such as yeast and other fungi, and the findings can then be used to understand cell division in higher organisms, including humans. My laboratory uses two fungi, the budding yeast Saccharomyces cerevisiae and the fungus Aspergillus nidulans, to identify and characterize genes and proteins that control cell division, particular mitotic entry, and exit. We are currently studying a gene in yeast, Kin3, which is a poorly understood member of the NIMA family of mitotic regulators. Using high-throughput robotics and molecular techniques, we have screened the entire budding yeast genome to identify genes that interact with Kin3, as part of an ongoing study to reveal genes and cellular processes that Kin3 affects. We are also studying two genes in Aspergillus nidulans which were originally identified in our laboratory and which are involved in regulating cell division. Mutation of one of these genes causes a lethal interaction with a mutation in nimA, the Kin3 homolog of Aspergillus nidulans and the first identified member of this mitotic regulatory family. These studies should lead to a better understanding of the mechanisms that control cell division in these organisms.

 

Planet earth is warming up. In some areas, such as the Polar Regions and tropical mountains,
species already appear to experience changes in their distribution. How species will react to the
increase in global temperature will determine the success of many current conservation
programs. For instance, the type of species found in a nature preserve may rapidly change. Thus,
a preserve currently set up to protect certain species of endangered birds, butterflies, bears,
plants, or other organisms, may loose many of the species it purports to protect as these species
react to changes in the climate by moving outside of the preserve boundaries. It is, therefore, in
our best interest to be able to predict future changes in species’ distributions. In my research I
use two different approaches to evaluate future changes in species distributions.

Zooarchaeological and/or paleontological data allow me to assess species ranges in the past
and relate them to past climatic conditions. This historical approach is necessary to calibrate
mathematical and geographic information system (GIS) models to a past benchmark; in other
words, it shows us what actually happened past climatic fluctuations. Faunal material (bones of
birds, reptiles, and amphibians) I am currently analyzing comes from the Santa Elena Peninsula
of Ecuador, as part of a NSF funded study, lead by Drs. Peter Stahl, SUNY Binghamton, and
Karen Stothert, University of Texas. This is a collaborative effort by researchers from three
continents. In the near future I am also hoping to analyze faunal material found at Millsaps
College’s Kaxil Kiuic Biocultural Reserve, Yucatan, Mexico.

Animals are limited in their distribution by many factors, some of which relate to their
physiological tolerance to bioclimatic conditions. Using the basal metabolic rate (BMR) as a
standardized measure of energetic requirements, I will establish associations between metabolic
rate and ecological and climatic variables. Some of this work is done in collaboration of Dr.
Brian McNab, University of Florida. I will concentrate my efforts on the Yucatan Peninsula and
the northwestern Andes of Ecuador. Although my main focus are birds, I hope to expand these
studies to bats as well.