Michelle Steinauer M.S. 1999 Southeastern Louisiana University Ph.D. Candidate   Email: UNLMichelle@aol.com

The effect of vicariance events of hosts on their parasites

Major Advisor: B. Nickol

Systematics and biogeography of the Leptorhynchoides thecatus (Acanthocephala: Rhadinorhynchidae) species complex

Leptorhynchoides thecatus is an acanthocephalan parasite of freshwater fishes. Collection of these parasites has uncovered geographically patterned variability in morphology, development, and biological characteristics, which indicates that L. thecatus may be comprised of multiple species. The first goal of this project is to identify and describe any distinct species within L. thecatus if they exist. Data for this analysis will be obtained from DNA sequences, morphology, and biological attributes of the parasites. The Internal Transcribed Spacer regions 1 and 2 (ITS) and a mitochondrial gene sequence will be used to create an intraspecific phylogeny of the group and a cluster analysis will be performed on the morphological data to elucidate cryptic species. Preliminary data from the ITS region indicate at least three distinct groups that correspond to host use, habitat use, and development.

The second goal of this study is to examine the biogeography of L. thecatus in relation to its hosts’ distributions. In the southeastern United States, freshwater fishes show distinct vicariant patterns at the interspecific and intraspecific levels. It is expected that coevolution between hosts and parasites will lead to concordant distibution patterns of their genetic variation. This concordance will be tested using a nested clade analysis which will be perfomed on the ITS and mitochondrial DNA sequences

The biogeography of the parasites of Lepomis (Pisces: Centrarchidae): the effect of vicariance events on the distribution of hosts and their parasites

The main goal of this project is to examine how vicariance events of hosts affect distribution patterns of their parasites. The distribution of fishes in the southeastern United States is divided into geographically distinct assemblages at the interspecific and intraspecific levels. It is hypothesized that this vicariant pattern developed from periodic changes in sea level that caused the retreat and isolation of organisms during high sea stands. Because parasites are intimately associated with their hosts, it is hypothesized that they share similar distribution patterns; however, biological attributes of the parasites such as host specificity, host use, and life cycle type may lead to non-concordant distributions. This project will explore this association at the interspecific and intraspecific levels and also the effects of the aforementioned characteristics on parasite distributions. At the interspecific level, parasite species assemblages of Lepomis spp. (sunfish) across the region will be investigated with a GIS analysis. The intraspecific analysis will involve a phylogeographic study of Leptorhynchoides thecatus, an acanthocephalan parasite that is widely distributed in Lepomis spp. and is morphologically and behaviorally variable throughout its range. This analysis will determine how the genetic variation of this species is allotted across its geographic range and in infrapopulations, metapopulations, and the suprapopulation.

Here's an image of the proboscis of Leptorhynchoides sp. nov. ("bald spot") from large-mouth bass (Apalachicola river)

More than anything, Michelle loves to fish, and no one beats her at getting bass!