Biological Sciences, School of

 

Date of this Version

Summer 8-1-2013

Comments

A THESIS Presented to the faculty of the Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Biological Sciences, Under the supervision of Professor Scott Lyell Gardner. Lincoln, Nebraska: August, 2013

Copyright (c) 2013 Ethan Thomas Jensen

Abstract

In this study, gerbils collected in the Mongolia over the summers of 2009-2012 were examined for coccidia. In total, 171 gerbils of three species from 22 localities were examined for coccidia. Coccidian oocysts were identified from 21 gerbils, but those found in 1 of those gerbils were probably pseudoparasites of the host from which they were recovered. From the remaining 20 gerbils, 7 morphotypes of Eimeria and 1 morphotype of Isospora were identified. Four of the 7 morphotypes of Eimeria were attributed to new species which were described in this study. In addition, 10 previously described species of Eimeria were recommended to be considered junior synonyms or species inquirendae. Phylogenetic analyses of the species of Eimeria identified in this study based on 9 continuous and 12 categorical morphological characters were then performed. The anaylsis which produced the highest consistency index (CI = 0.6667, excluding uninformative characters) used all data with unweighted character states and produced 3 equally parsimonious trees. However, the tree score distribution for this analysis was only weakly skewed right with a g1 value of −0.25439, indicating a lack of phylogenetic information. The analysis which produced the most strongly right skewed tree score distribution (g1 = −0.4950) used only categorical data with characters weighted inversely to the number of states and produced seven equally parsimonious trees. In order to predict the spatial distribution of Eimeria spp. occurring in gerbils in Mongolia and identify any apparent ecological trends, ecological niche models (ENM’s) were produced using both GARP and Maxent, and chi-squared tests were performed to identify correlations between infection with species of Eimeria or Isospora and host species, sex, infection with helminths, and year and month of capture. ENM’s produced with GARP predicted that Eimeria spp. occur in 28.63% of Mongolia, while the model produced with Maxent predicted the Eimeria spp. occur in 28.70% of Mongolia. The environmental variables with the greatest percent contribution to the ENM predicting the distribution of Eimeria spp. created with Maxent were Normalized Differential Vegitative Index (NDVI), mean precipitation of the driest month, and aspect. The only significant (α=0.10) correlation found using a chi-squared test was that between host species and infection by Eimeria spp. (p=.07); oocysts of Eimeria spp. were recovered from 5% of hosts of Meriones meridianus and 14% of hosts of Meriones unguiculatus. The additions and revisions to the taxonomy of the coccidia of gerbils in this study contribute to the knowledge base of host-parasite associations which may serve as a foundation for future studies in a wide variety of fields, and while the distributions predicted and phylogenies produced in this study are tentative, they may serve as a starting point for future investigators.

Advisor: Scott L. Gardner