Shem D Unger
Purdue University
Dept. of FNR West Lafayette, IN 47906
phone: (765) 414-5435
email: sunger@purdue.edu
Research Interests:
My PhD research is on the ecology, genetic variation, and population status of the eastern hellbender (Cryptobranchus alleganiensis alleganiensis) in the Blue River, IN. These long-lived salamanders inhabit clear, cool streams with a mosaic of larger shelter rocks and gravel substrate for nest construction and larval development. Hellbender populations are in severe decline throughout their range due to increased siltation, water pollution, over-collection, and mortality by anglers. Indiana populations once found throughout the Wabash and Ohio River watersheds, are now restricted to the Blue River. Because this decline is likely the result of multiple causative agents, we will utilize a combination of field sampling techniques, laboratory simulation, and molecular marker development to investigate hellbender ecology and genetics.
Current Projects:
Diet of hellbender adults and larvae in Indiana and regionally
Relationships among trophic levels within lotic systems are complex. While adult hellbenders are known to feed predominantly on crayfish, information regarding juvenile prey base is lacking. We will use quantitative enclosures to sample dominant substrate habitats and estimate crayfish/macro-invertebrate diversity and abundance within hellbender home ranges. We will compare food availability on a local and regional scale.
Genetic variation and conservation genetics
Molecular markers (short tandem repeats) have recently become a powerful tool in conservation biology. We will use these polymorphic microsatellite markers to examine genetic variability between and within populations. Measures of genetic variability to examine include allele frequencies, observed and expected heterozygosities (Ho and He), inbreeding estimates (Fst), and fluctuations from Hardy-Weinberg equilibrium (HWE). Effective population size (Ne), often a more effective indicator of evolutionary potential, derived from our genetic analysis, will be compared with population census size (Nc), calculated from our mark-recapture study. Microsatellite data will be used to calculate the mean ratio of allele number to allele range (M-ratio) to detect evidence of recent reductions in population size (bottlenecks). Microsatellite library development will also allow for identification of source stock populations for future DNR augmentation efforts.
Population modeling
Populations exhibiting a combination of low gene flow and little recruitment may be at risks for reduced reproduction success and eventually extinction. Continually declining and increasingly fragmented population are more at risk for the deleterious effects of inbreeding depression. With the aid of Trent Sutton we will develop a stage-structured population model to examine the effects of sex ratios, reproductive success, growth, and body condition on hellbender viability. Information from our mark-recapture study and demographic parameters from previously published studies will be incorporated into the model. Environmental stressors, potential threats, and rehabilitation efforts will be simulated in the model to identify critical factors among life history stages and identify the greatest risks to long-term population viability.
Presentations given at professional meetings:
2005 Klamath Lamprey Conference and Workshop. Shasta and Scott River lamprey project. Arcata, California.
2003Hellbender Conference. Reproductive biology of hellbenders. Helen, Georgia.
2003 International Herpetological Conference. Reproductive biology of hellbenders. Manuas, Brazil.
2003 Southwestern Association of Naturalists. Reproductive biology of hellbenders. Norman, Oklahoma.
2003 Ozark Hellbender Working Group. Comparison of Sperm Parameters for male hellbenders. Mammoth Springs, Arkansas.
2002 Missouri Herpetological Society. Associative learning by gray-bellied salamanders. Steelville, Missouri.
2002-3 SMSU Interdisciplinary Forum for Graduate Research. Hellbender Reproduction and Conservation. Springfield, Missouri.
