Date of Award

Summer 8-2022

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biological Sciences

Program/Concentration

Ecological Sciences

Committee Director

Lytton J. Musselman

Committee Director

Eric L. Walters

Committee Member

Christopher P. Randle

Committee Member

Daniel J. Barshis

Abstract

Mistletoes are shrubs that typically parasitize the branches of host trees and rely on avian frugivores for seed dispersal. Because mistletoes are restricted to a narrow range of suitable recruitment sites and avian frugivores are more visible than other guilds of seed dispersers, mistletoe-frugivore systems afford opportunities for assessing the roles of dispersal limitation and local environment in determining plant distribution. These mechanisms have been proposed as determinants of the observed association of oak mistletoe [Phoradendron leucarpum (Raf.) Reveal & M. C. Johnst.] with forested wetlands in eastern Virginia and North Carolina, USA. I tested the alternative hypothesis that variation in host availability drives this habitat relationship, instead finding a significant positive effect of forested wetland habitat on oak mistletoe occurrence after correcting for differences in host availability.

I used a community occupancy model to analyze avian occurrence data and estimate species-specific relationships between disperser occurrence and forested habitat type. I did not find statistically significant relationships between occurrence and forested wetland habitat for either of the two principal dispersers of oak mistletoe in the study area, the eastern bluebird (Sialia sialis) and cedar waxwing (Bombycilla cedrorum). While these results suggested avian dispersers to be more widespread with regards to habitat type than oak mistletoe, the potential remained for these species to show cryptic habitat specificity. As such, I looked at patterns of oak mistletoe genetic structure versus habitat type. Analyses showed evidence for gene flow across habitat types and the presence of a genetically distinct population of oak mistletoes restricted to hosts in the genus Nyssa L.

I used seed sowing experiments to quantify the roles of light availability and flood regime in determining the initial survival of oak mistletoe. These experiments allowed me to evaluate the potential for establishment limitation to determine variation in oak mistletoe occurrence across different forested habitats. I found support for a relationship between manipulated local light availability conditions and seedling establishment rates. Variation in oak mistletoe establishment success across forested habitat types is a potentially important mechanism in determining observed habitat relationships in oak mistletoe.

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DOI

10.25777/6h7t-f859

ISBN

9798352695197

ORCID

0000-0003-1934-7779

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