Author ORCID Identifier

https://orcid.org/0000-0003-0227-1982

Date Available

5-8-2024

Year of Publication

2024

Document Type

Doctoral Dissertation

Degree Name

Doctor of Philosophy (PhD)

College

Arts and Sciences

Department/School/Program

Biology

Advisor

Dr. Jeremy Van Cleve

Co-Director of Graduate Studies

Dr. Steven J. Price

Abstract

Metapopulations are shaped by the dispersal between populations in a landscape. Disturbance events can disrupt this connectivity resulting in local population extinction. For my dissertation, I used a combination of empirical and theoretical techniques to examine dispersal in response to disturbance and assessed it’s population-level consequences. My research used capture-mark-recapture sampling techniques to evaluate stream salamander movement in response to (1) a supraseasonal drought and (2) mountaintop-removal-mining (MTR) and valley-filling (VF) and (3) agent-based simulation modeling to evaluate population extinction risk in response to varying dispersal and mortality rates.

First, I evaluated the effects of a supraseasonal drought, a severe drought that occurs outside of predictable seasonal dry periods for an extended period of time, on the movement frequency distribution, survival, and growth rates of adult Desmognathus fuscus. I found that salamanders were more likely to move immediately after the supraseasonal drought compared to before or during the drought. Salamanders who moved experienced slightly higher growth rates post-drought. Although movement frequency was low during the drought, survival was higher for individuals who moved in comparison to individuals who remained in their original capture location. My results suggest that adult salamanders were potentially displaying an adaptive movement strategy to resist drought conditions by moving away from affected (i.e., dry) areas within the study stream during the drought and moving towards replenished resources in other areas after the drought ended.

Next, I evaluated movement pathways (e.g. within-stream, overland), movement frequency distribution curves, individual body condition, and dispersal rates for two common stream salamander species (D. fuscus and D. monticola) within a reclaimed MTR and VF landscape and compared these populations with populations from an undisturbed, reference landscape. I found that stream salamanders utilized within-stream dispersal pathways in the reference and MTR and VF landscape. However, overland movement was only detected in the reference landscape, not in the MTR and VF landscape. Body condition was a potential driver for individuals engaging in dispersal and was overall lower for individuals in the MTR and VF landscape compared to the reference landscape. My results indicated that overland connectivity between salamander populations in the MTR and VF landscape was disrupted compared to the undisturbed landscape and resulted in population isolation, which, if left unchanged, could result in local population extirpation.

Finally, I constructed two agent-based models with different metapopulation structures and investigated how differences in extinction risk was affected by differences in dispersal and mortality probabilities between populations and between areas. I found that differences in dispersal and mortality did influence population extinction risk. My models demonstrated that increased dispersal into a population decreased it’s extinction risk but only when population differences in mortality was low. In addition, when mortality was higher for an area, populations located on the fringe of the metapopulation network had a higher extinction risk compared to the populations that bordered other populations. My results indicated that maintaining connectivity between populations lowers population extinction risk, especially in areas of lower habitat quality resulting from a disturbance event.

This research demonstrates that long-distance movement allows populations to resist the negative effects of environmental and anthropogenic disturbance. Therefore, maintaining and, when applicable, restoring both aquatic and terrestrial habitat is likely vital for stream salamander population persistence.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2024.80

Funding Information

  • Kentucky Society of Natural History Research Grant. 2020.
  • National Science Foundation Graduate Research Fellowship Program. 2019.
  • Eller Billings Summer Research Mini-Grant, UK Appalachian Center Research Grant. 2019.
  • University of Kentucky’s Biology summer Fellowship Summer Research Grant. 2018.
  • Gertrude Flora Ribble Research Fellowship. 2018.

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