Dispersal Effects on Species Distribution and Diversity Across Multiple Scales in the Southern Appalachian Mixed Mesophytic Flora Public Deposited

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  • March 20, 2019
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  • Tessel, Samantha
    • Affiliation: College of Arts and Sciences, Curriculum in Environment and Ecology
Abstract
  • Seed and spore dispersal play important roles in the spatial distribution of plant species and communities. Though dispersal processes are often thought to be more important at larger spatial scales, the distribution patterns of species and plant communities even at small scales can be determined, at least in part, by dispersal. I studied the influence of dispersal in southern Appalachian mixed mesophytic forests by categorizing species by dispersal morphology and by using spatial pattern and habitat connectivity as predictors of species distribution and community composition. All vascular plant species were recorded at three nested sample scales (10000, 1000, and 100 m2), on plots with varying levels of habitat connectivity across the Great Smoky Mountains National Park. Models predicting species distributions generally had higher predictive power when incorporating spatial pattern and connectivity, particularly at small scales. Despite wide variation in performance, models of locally dispersing species (species without adaptations to dispersal by wind or vertebrates) were most frequently improved by the addition of spatial predictors. Patterns in plant communities were also compared among dispersal categories, and though it was shown that species without dispersal adaptations were less likely to co-occur, this was more likely to be caused by differences in frequency across dispersal categories than by dispersal limitation per se. Spatial pattern, distance, and connectivity were significant predictors of non-random patterns of species turnover at all scales and were stronger among dispersal-limited species groups. Species with limited dispersal were also less frequent at all three sampling scales than those with adaptations for vertebrate dispersal and had smaller geographic ranges than either wind- or vertebrate-dispersed species. Species with no dispersal adaptations were overrepresented among southern Appalachian endemics and lineages endemic to North America, whereas species dispersed by vertebrates were overrepresented among Tertiary disjunct lineages, and species dispersed by spores were cosmopolitan. Relationships among dispersal and biogeographic affinity reflect the evolutionary history of the mixed mesophytic flora owing to adaptation of dispersal mechanisms to regional environmental conditions, the relative ages of lineages, and the effect of dispersal mechanism on the distributions of plants across time and space.
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  • In Copyright
Advisor
  • Peet, Robert K.
  • Weakley, Alan S.
  • Urban, Dean
  • Hurlbert, Allen
  • White, Peter
Degree
  • Doctor of Philosophy
Degree granting institution
  • University of North Carolina at Chapel Hill Graduate School
Graduation year
  • 2017
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