Absence of Host-Associated Differentiation in the Rhopalomyia solidaginis and Solidago Relationship in Western Pennsylvania

Deicke, Matthew

Absence of Host-Associated Differentiation in the Rhopalomyia solidaginis and Solidago Relationship in Western Pennsylvania

Persistent URL

http://hdl.handle.net/10456/36001

Author(s)

Deicke, Matthew

Date Issued

March 31, 2014

Abstract

A sub-genre of cospecies evolution, known as host-associated differentiation (HAD), involves speciation attributed to a loss of gene flow between subpopulations of parasites due to varying preference for host organisms. Subpopulations of the galling midge, Rhopalomyia solidaginis, primarily parasitize both Solidago gigantea and Solidago altissima goldenrod; however, patterns of HAD have been observed in the Midwest United States by assessing the genetic diversity between host preference subgroups. Studying a previously unsurveyed geographic area helps to generalize the implications that host preference plays in the speciation of this galling midge. R. solidaginis samples were taken from old-fields in Pittsburgh, PA and Meadville, PA. Cytochrome oxidase 1 (COXI) sequences were then used in bioinformatic comparisons. Statistical tests, including Maximum Likelihood (ML) tree reconstruction and Analysis of Molecular Variance (AMOVA), did not lend support to the presence of HAD and population substructure in Western Pennsylvania. Analyses of variable site degeneracy lacked support for the presence of positive selective pressures imposed on the gall midge to shift hosts, regardless of the existence of R. solidaginis’s parasitoid wasp, Platygaster variabilis, which has been attributed to the host shift observed in the Midwestern United States. This result thus modifies the understanding of HAD as being a universal speciation mechanism, and supports the fact that it may instead occur in more geographically isolated instances.

Honors

Biology, 2014

First Reader(s)

Webb, Kristen