The role of geography in the evolution of gamete incompatibility in hybridizing blue mussels

UNCW Author/Contributor (non-UNCW co-authors, if there are any, appear on document)
Christin T. Slaughter (Creator)
Institution
The University of North Carolina Wilmington (UNCW )
Web Site: http://library.uncw.edu/
Advisor
Mike McCartney

Abstract: The examination of natural hybridization and hybrid zones are useful tools to examine the evolution of prezygotic and post zygotic mechanisms through which reproductive isolation develops in marine environments that typically lack the absolute physical barriers that are requisite for traditional allopatric models of genetic differentiation thought to lead to species formation. For blue mussels species that readily hybridize in areas of sympatry, post zygotic mechanisms have been the focus of the majority of investigations addressing isolating mechanisms. However, for free-spawning marine invertebrates, gametic incompatibility can facilitate the evolution of “complete” reproductive isolation in sympatric species through the strengthening of prezygotic isolating traits as a result of selection against hybrids and hybridization (i.e. reinforcement). The reinforcement of pre-mating isolation, as evidenced by a pattern of reproductive character displacement, was investigated in the hybridizing blue mussels, Mytilus edulis and M. trossulus within the Gulf of Maine. Using in vitro fertilization experiments, a simple comparison was made evaluating levels of heterospecific gamete compatibility, in allopatric, M. edulis females, compared to M. edulis females from a sympatric, hybridizing, population. Partial compatibility of M. edulis females in heterospecific crosses was observed in both sympatric and allopatric populations, however in a pattern opposite to that expected under a theory of reinforcement. Mytilus edulis females from allopatric populations were more strongly blocked to heterospecific fertilization than M. edulis females from sympatric populations. The absence of a signal of reproductive character displacement consistent with the process of reinforcement suggests that the “atypically” compatible female found in sympatric populations may be a product of introgression, with highly introgressed individuals undetected at the current level of resolution available. The absence of reproductive character displacement should not, however, eliminate the role that reinforcement may play in the pattern of interbreeding, and non-fusion, in these hybridizing species. A comparison of patterns in heterospecific gamete incompatibility between western and northeastern Atlantic hybrid zones may prove to be valuable for studying the process of reinforcement, as well as lead to a greater understanding of the role of hybridization in species formation.

Additional Information

Publication
Thesis
A Thesis Submitted to the University of North Carolina at Wilmington in Partial Fulfillment Of the Requirements for the Degree of Master of Science
Language: English
Date: 2009
Keywords
Mussels--Effect of environment on, Mussels--Reproduction, Mutation (Biology), Mytilidae--Effect of environment on, Mytilidae--Reproduction
Subjects
Mussels -- Effect of environment on
Mussels -- Reproduction
Mutation (Biology)
Mytilidae -- Effect of environment on
Mytilidae -- Reproduction