Theses and Dissertations

Issuing Body

Mississippi State University

Advisor

Counterman, Brian A.

Committee Member

Brooks, Christopher P.

Committee Member

Brown, Richard L.

Committee Member

Vilella, Francisco

Committee Member

Welch, Mark E.

Date of Degree

1-1-2015

Document Type

Dissertation - Open Access

Major

Biological Sciences

Degree Name

Doctor of Philosophy

College

College of Arts and Sciences

Department

Department of Biological Sciences

Abstract

There is repeated evidence that hybridization is a major contributor to the production of adaptive diversity; however, the evolutionary fate of hybrids in natural populations remains poorly understood. In Heliconius butterflies, hybridization is common and responsible for generating a variety of warning color patterns across the genus. Predator avoidance of warning colorations appears to largely be learned, which drives strong positive frequency-dependent selection. This creates a paradox for hybrid lineages: how do novel hybrid forms manage to establish and persist under such strong selection? In this dissertation, I present a series of studies centered on the selection dynamics of Heliconius hybrid zones, to elucidate how novel adaptive traits establish in nature. Clines across hybrid zones have often been analyzed to estimate selection on ecologically important loci. Here, warning color clines were characterized and compared across multiple transects along a Heliconius hybrid zone in the Guiana Shield. Furthermore, a mark-resight experiment and communal roost observations were completed near the center of this hybrid zone to determine the survival and likelihood of establishment of native and foreign forms. These studies reveal similar survivorship of hybrid and pure color patterns, and specifically demonstrate that a rare putative hybrid form can survive and establish within a hybrid zone. Both hybrids and pure color patterns showed comparable life expectancies in the mark-resight experiment and similar patterns of presence at nocturnal roosts. These results suggest that selection on warning color pattern is relatively weak within the hybrid zone. Analyses of color pattern clines uncovered strong selection bounding the hybrid zone in bi-race areas, while weaker selection was estimated for a tri-race area. In fact, the tri-race area was three times wider than the bi-race areas. Collectively, these studies suggest that the selection dynamics across hybrid zones may play an integral role in the establishment of new adaptive traits, and offers a route by which a reputed hybrid race may have arisen. The investigations within this dissertation also provide a new view of hybrid zone dynamics, and improve our understanding of how hybridization and selection shapes the evolution of biodiversity.

URI

https://hdl.handle.net/11668/19613

Comments

genotype criteria||communal roosting behavior||cline analysis||mark-resight||frequency-dependent selection||warning coloration||Heliconius||adaptive variation||hybrid zones||artificial butterfly models

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