Lizard community structure across a grassland – creosote bush ecotone in the Chihuahuan Desert

Abstract

I investigated the distribution and abundance of lizard species (Aspidoscelis inornatus, Aspidoscelis tesselatus, Aspidoscelis tigris, Aspidoscelis uniparens, Cophosaurus texanus, Crotaphytus collaris, Eumeces obsoletus, Gambelia wislizenii, Holbrookia maculata, Phrynosoma cornutum, Sceloporus magister, and Uta stansburiana) across a desert grassland – creosote bush (Larrea tridentata) ecotone in Dona Ana County, New Mexico. The ecotonal area in the Jornada del Muerto basin has increased dramatically in the past 150 years because of the rapid spread of creosote bush. I asked four related questions: how large and where is the ecotone based on vegetative structure, and do lizard abundance and diversity change across the ecotone? Vegetation data were analyzed using discriminate function analysis to determine the extent of the ecotone. Changes in lizard abundance across the ecotone were analyzed by analysis of variance. During two summers, 677 individual lizards of 9 genera and 12 species were captured. Lizard abundance increased with increasing distance from the ecotone and was similar in grassland and creosote bush habitat. Grasslands had higher species richness than both the creosote bush and ecotone habitats. Grassland sites had greater habitat heterogeneity than did creosote bush sites. No ecotone specialist species were detected, and all common lizard species could be found in each habitat. Three potential explanations for decreased abundance in the ecotone are presented: (1) increased risk of predation, (2) decreased prey abundance, and (3) lack of species-specific microhabitat requisites.

Effects of livestock removal and perennial grass recovery on the lizards of a desertified arid grassland

“…At a similar grazing exclosure also in southeastern Arizona, where there is a cross-fence difference in vegetation, Bock et al (1990) found the lizard Sceloporus scalaris to be less abundant outside the livestock exclosure; the authors posited increased predation due to decreased vegetation complexity was responsible for the disparity. Another study in similar Chihuahuan desert habitat in southwestern New Mexico also posited that changes in lizard abundance across a gradient of vegetation complexity were due to variation in predation (Menke, 2003). Therefore we used one-tailed binomial tests to compare cross-fence relative number of tail-breaks for each species.…”

“…Mechanisms that may produce this relationship include increases in niche separation (Schoener, 1974;Fischer et al, 2004), variation in prey abundance (Vitt and Ohmart, 1977) and variation in predation risk (Bock et al, 1990;Menke, 2003). However, we do not know of any empirical tests of either the prey abundance or predation mechanisms.…”

Three Species of Ectoparasite Mites (Acari: Pterygosomatidae) Infested Geckos in Indonesia

“…Groups of gecko migrated between islands through human activity (Jesus et al 2001). Human activity leads to vegetation changes and trigger migration of Geckonidae species (Menke 2003). In Florida, acceleration in the population of invasive H. garnotii could replace the native species (H. tursicus) (Meshaka 2000).…”

Vulnerability of species to climate change in the Southwest: terrestrial species of the Middle Rio Grande

“…We expect riparian associates including checkered gartersnake, blacknecked gartersnake, desert spiny lizard (Menke 2003;Vitt and others 1981), Chihuahuan spotted lizards (Catron and others 2008), and checkered whiptail to be negatively impacted by declines of associated habitat. Coachwhips, though they depend on open grasslands and thick clumps of vegetation, also are reported to be sensitive to fragmentation (Mitrovich and others 2009), and we considered this species likely to experience disruption to their preferred habitat with potential negative effects on population size.…”