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The evolutionary history of interactions among short -tailed shrews (Blarina Gray, 1838) and their parasitic trichostrongylid nematodes (Longistriata Schulz, 1926)

Sara Vanessa Brant, University of Nebraska - Lincoln


This research offers the first comprehensive evolutionary framework for short-tailed shrews and their nematodes. The individual and collective evaluation of shrews and nematodes proved to be invaluable to understanding patterns and inferring coevolutionary processes that may have shaped this symbiotic relationship. The link between microevolutionary studies and macroevolutionary studies has been mired by the lack of phylogenetic framework, a requisite for all research programs that utilize the comparative method. The primary approach of this study was to reconstruct the phylogenetic relationships using mitochondrial DNA(mtDNA) markers among three congeners of trichostrongylid nematodes (Longistriata) and their hosts, short-tailed shrews (Blarina). The limited distribution of the hosts and commonness of the nematodes make this system ideal for coevolutionary study. Phylogenetic analyses of mtDNA haplotypes characterized for the three species of shrews resulted in monophyletic groups for each species. Additional analyses investigating the phylogeographic relationships among one species of shrew, Blarina brevicauda resulted in distinct western and eastern groups. The life history of the short-tailed shrews predicted that the phylogeographic structure within the nematodes occurring in a host with low vagility, no intermediate hosts, and with no mobile free-living stages should show a cophylogenetic pattern. Analyses at two levels were conducted to test the above prediction, a microevolutionary analysis of one species of nematode within a contact zone between two species of short-tailed shrews and a macroevolutionary analysis between three groups of congeneric nematodes and all three species of hosts. The microevolutionary analysis resulted in a parasite pattern that was discordant with that of its host. The macroevolutionary analysis resulted in a coevolutionary pattern between two species of host and two groups of nematodes, as predicted. There was no association by host or geography in the third group of nematode. This study is the first to include a complete sampling of hosts and parasites and to compare the genealogical micro-and macroevolutionary patterns significant in contributing to understanding the evolutionary history of this symbiotic relationship. ^

Subject Area

Biology, Molecular|Biology, Zoology

Recommended Citation

Brant, Sara Vanessa, "The evolutionary history of interactions among short -tailed shrews (Blarina Gray, 1838) and their parasitic trichostrongylid nematodes (Longistriata Schulz, 1926)" (2002). ETD collection for University of Nebraska - Lincoln. AAI3059939.