PS 33-1 - Correlation of habitat factors and presence or absence of eastern collared lizards

Wednesday, August 10, 2011
Exhibit Hall 3, Austin Convention Center
Ashley A. Grimsley, Biological Sciences, University of Arkansas, Fayetteville, AR and Gary R. Huxel, Department of Biological Sciences, University of Arkansas, Fayetteville, AR

Crotaphytus collaris collaris (eastern collared lizard) distribution includes southwestern United States, Northern Mexico and peripheral locations in the Ozark Mountains. The peripheral Ozark populations have declined strongly mainly due to wildfire suppression.  Decreased fire has resulted in increased cedar encroachment in rocky glades, the preferred habitat of C. c. collaris in the Ozark region.   The total available habitat has dramatically declined resulting in smaller populations, including local extirpations, and greater isolation.  

To determine habitat requirements for the C. c. collaris, two questions were developed: (1) What habitat structure features are associated with the presence of C. c. collaris populations? (2) Are there habitat structure differences between lizard and non-lizard sites? Previous studies have shown that C. c. collaris prefers open rocky habitat avoiding closed canopy sites. 

The study area consisted of the River Valley and Ozark regions of Arkansas. The sampling method included a habitat survey using a line-transect method at six glade sites that were previously known to have C. c. collaris populations. Two transects, 25 m long, were sampled every meter to estimate canopy cover. Percent ground cover of rock, vegetation, and bare soil was estimated using 4 m-squared  quadrats every five meters along the same transect. 


A PCA was carried out using PC-ORD© to determine the relationship among glade sites due to habitat variables. The first two axes explained approximately 98% of the variance.  There was not a significant difference (P>0.1) in habitat variables among all sites. However, there was a strong grouping of sites with lizards and sites without; study sites with lizard presence were negatively associated with canopy cover and bare soil and positively correlated with plant cover and bare rock. 

An analysis of variance was carried out using the first axis scores of the PCA to examine the influence of habitat factors on lizard presence/absence. There was a significant difference (F=0.0112) among sites with and without lizards with 83% of variation explained, indicating sites with high ground cover and low canopy cover are preferred.

These results suggest that fire suppression leading to increased cedar canopy cover has decreased the habitat quality for C. c. collaris and increased isolation resulting in extirpation over much of the former suitable glade habitat in the Ozark region.  Identifying specific site characteristics and lizard habitat and diet requirements will benefit development of restoration protocols in glades aimed at C. c. collaris recovery.

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