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Title:Population genetics of the Illinois chorus frog (Pseudacris illinoensis)
Author(s):Schneider, Ellen
Advisor(s):Phillips, Christopher A.
Department / Program:School of Integrative Biology
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Pseudacris illinoensis
Illinois chorus frog
population genetics
habitat loss
founder effects
Abstract:The Illinois chorus frog (Pseudacris illinoensis) is a fossorial species found only in sandy substrates of Illinois, Missouri, and Arkansas. The genetic diversity of the Illinois chorus frog (ICF) in Illinois has not been investigated prior to this study. Given its conservation status and the vulnerability of its ephemeral sand pond habitat, more knowledge about the genetic diversity of the ICF and its habitat use is necessary. The goals of this study were twofold, first, to assess the genetic diversity of the ICF in central Illinois (Mason and Tazewell counties) and secondly to assess the level of philopatry in the ICF. A total of 479 samples were collected from ponds in Mason, Tazewell, Menard, and Alexander counties in Illinois. Four microsatellite loci, originally developed for the ornate chorus frog (P. ornata) by Degner et al (2009), were used to evaluate genetic diversity in ICF at two levels: a local focus of geographically close ponds (called “clusters”) and a regional perspective at the county level (referred to as “counties”). Samples were partitioned into seven clusters, with five in Mason County and two in Tazewell County. Within clusters, heterozygosity was low (Range of HO for all loci in clusters: 0.03-0.10). Inbreeding coefficients could not be estimated with statistical confidence, because of insufficient data (i.e., small sample sizes, only four loci evaluated). However, three clusters showed deviations from Hardy Weinberg Equilibrium (HWE), potentially resulting from null alleles at two loci; results should therefore be treated with caution. Pairwise FST estimates showed slight genetic structure among clusters and a high FST between two clusters about 46 kilometers apart. Private alleles were detected in six of the seven clusters (i.e., alleles unique to a particular cluster and not found in any others). Heterozygosity was low (Range of HO for all loci: 0.03-0.19) in the counties. Three of four counties were not in HWE, likely due to the Wahlund effect. This suggests the potential presence of subtle population structure at the regional scale. Detection of low heterozygosity and slight population structure between clusters indicate low levels of gene flow and philopatric behavior in the ICF. The heavily agricultural nature of the study areas might be impeding movement of the ICF, further exacerbating genetic drift and founder effects. Additional population genetic work evaluating more loci and a larger number of ponds/samples, combined with a field study employing traditional tracking or mark/recapture methods will be necessary to better estimate genetic diversity and habitat use of the ICF. These data will be needed for management to ensure long-term survival of the ICF.
Issue Date:2012-02-01
Rights Information:Copyright 2011 Ellen Schneider
Date Available in IDEALS:2014-02-01
Date Deposited:2011-12

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