Dissertation/Thesis Abstract

Sky-island in the Mojave Desert: Demography of high and low elevation populations of Sceloporus occidentalis
by Hooper, Charles, Jr., M.S., California State University, Long Beach, 2016, 94; 10196448
Abstract (Summary)

Ord Mountain is a sky island found in the Mojave Desert. Populations are isolated from one another on sky islands and may differ in population size, body size, and behavior. On Ord Mountain, S. occidentalis populations are present from the top of the mountain (1925m) to near the bottom (1330m), but are absent from the desert floor (<1300m). The purpose of this study was to determine how abiotic factors (temperature and precipitation) affect population size, recruitment, and body size of lizards at high and low elevations using one-hectare sampling grids. Precipitation was highest in 2010, but declined from 2011-2013 and did not exceed more than 3cm throughout the year. Low temperatures and precipitation delayed the start of the breeding season at Upper Ord, but allowed for a longer activity season. At Lower Ord, the decline in rainfall caused high temperatures to occur earlier which shortened both daily and seasonal activity. Mark-recapture methods were used to estimate population sizes throughout the study period. Lizards were measured to determine changes in body size among years for adults, juveniles, and young-of-the-year (YOTY). Population size at Upper Ord declined by 52% from 2010-2013 (108 to 51), but population size estimates at Upper Ord were always larger than those at Lower Ord by approximately 2-fold from 2011-2013. At Lower Ord, population size estimates declined by 32% from 2012-2013. Adults, juveniles, and YOTY survivorship percentage increased across years, however, population size estimates reached their lowest levels in 2013 No YOTY were captured at either site in 2013. There was significant difference across years for SVL in adults and YOTY at both elevation sites. Temperature and precipitation may have limited movement of lizards both within the same year and between years. Precipitation had the greatest impact on population size estimates and demographic structure.

Indexing (document details)
Advisor: Archie, James
Commitee: Carter, Ashley, Lappin, Kristopher
School: California State University, Long Beach
Department: Biological Sciences
School Location: United States -- California
Source: MAI 56/02M(E), Masters Abstracts International
Subjects: Biology
Publication Number: 10196448
ISBN: 978-1-369-35638-0
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