Slide 1: Title: Mechanisms behind the successful invasion of American Bullfrogs (Rana catesbeiana) in the Northwest United States
Tiffany Garcia, Chris Funk, Selina Heppell, Andrew Blaustein,
Rebbecca Hill and Bert Cortina
Department of Fisheries and Wildlife
Slide 2: Invasive Species
Pressing Ecological Question:
What mechanisms allow exotic species to invade and establish in novel environments?
- American beach grass
- Nutria
- European starling
- Himalayan blackberry
- New Zealand Mudsnail
- Red swamp crayfish
Slide 3: Invasive Species
Pressing Ecological Question:
What mechanisms allow exotic species to invade and establish in novel environments?
- Canary Reed Grass
- Sudden Oak Death
- Feral Pig
- European Green Crab
- Yellow star thistle
Slide 4: Invasive Species
Pressing Ecological Question:
What mechanisms allow exotic species to invade and establish in novel environments?
- Bullfrog
Slide 5: Bullfrog background information
Native Range:
- Eastern North America
Invasive Range:
- Western North America
Mechanism:
- Frog farms
- Pet release
Slide 6: Bullfrog background information
Invasion impacts
Invasive Bullfrogs can negatively impact native species
examples: Rana draytonii, R. yavapaiensis, R. chiricahuensis
Joseph M. Kiesecker et al. (2001)
- Adult bullfrogs reduce larval Red-legged growth and survival rates
- Context dependent: respond only when habitats are disturbed
Mike Adams et al. (2003)
- Invasion of bullfrogs in the PacNW is facilitated by the presence of non-native fish
- Non-native fish reduce predatory macroinvertebrate densities
Slide 7: Chart: Comparison of Life History Characteristics
Slide 8: Bullfrog background information
Pilot study: S.S. Heppell
Experiment reared tadpoles from E.E. Wilson ponds
Slide 9: Bullfrog background information
Pilot study: S.S. Heppell
- Experiment reared tadpoles from E.E. Wilson ponds
- Tadpoles from permanent ponds did NOT develop faster under ephemeral conditions
- Tadpoles from ephemeral ponds DID devolop faster under ephemeral conditions
Slide 10: Hypotheses
3 hypotheses for successful establishment
1. Local adaptation to novel environment
Phenotypic divergence is genetically based
Invasive population has adapted to local conditions
2. Phenotypic plasticity in response to novel environmental conditions
Phenotypic divergence is environmentally induced
Individuals across populations can plastically adjust phenotype
3. Invasive acts as disease reservoir
Invasive species are carriers of a pathogen
The introduced disease decreases fitness of natives and facilitates the carrier’s invasion
Slide 11: Hypotheses
Invasive acts as disease reservoir
- Batrachochytrium dendrobatidis (BD) is a chytrid that attacks amphibians
- BD is found on all continents and has species specific infection rates
- Bullfrogs may be a carrier for BD
Slide 12: Chart: Predictive model
Slide 13: Research project
Objective 1: Determine the source population(s) of invasive bullfrogs in the Pacific Northwest
Methods: Use molecular markers to determine the geographic origin of source population(s) within the native range.
- mtDNA markers
- microsatellite
Slide 14: Illustration: Bullfrog tissue collection
Slide 15: Chart: Results: Objective 1
Slide 16: Results: Objective 1
Source Region:
- mtDNA analysis points to Mississippi River Valley haplotypes
- Austin Haplotype data in GenBank (Austin et al. 2004)
Novel environmental Factors:
- temperature
- altered hydrological regimes
Slide 17: Research project
Test Invasion Hypotheses:
- Local Adaptation
- Phenotypic Plasticity
- Disease Reservoir
Slide 18: Research project
Objective 2: Determine whether divergence in larval bullfrog phenotypes is genetically based
Methods: Large-scale Common Garden Experiment
- collect eggs from 2 Invasive and 2 source populations
- rear larvae in 2 temperature and 2 hydroperiod treatments
Design- 2x2x4 full factorial
- 4 populations
- 2 temperatures
- 2 hydroperiods
Quantify
- Growth Rate
- Time till Metamorphosis
- Morphometrics
Slide 19: Research project
Objective 3: Test whether bullfrogs can infect native amphibians with Batrachochytrium dendrobatidis (Bd)
Methods: Bd Exposure Experiment
- Expose native individuals to infected bullfrog individuals
- Quantify mortality
- Quantify infection using PCR
Slide 20: Significance
How do you stop bullfrog invasions? Depends….
- Local adaptation
- Delayed expansion into novel environments
- Time to adapt management plans
- Phenotypic plasticity
- Expansion only limited by dispersal speed
- Run for the hills
- Disease reservoir
- Target the pathogen
-
Bullfrog invasive range will have little/no overlap with native frogs
Slide 21: Map: Results
Expand Analysis to Global Bullfrog Distribution
Slide 22: Significance
Send me tissue samples!!!
Tiffany Garcia
tiffany.garcia@oregonstate.edu
Dept. of Fisheries and Wildlife
Slide 23: Acknowledgments
Dave Paoletti, Beth Hultman, Becky Hill, Chris Funk, Phil Rossignol, Randy Colvin, Anduy Blaustein
Additional Field Assistants: Sarah Abdulkarim,
Scott, Selina & Dylan Heppell,
Rob Hultman
For more information about this presentation, contact: tiffany.garcia@oregonstate.edu