Cristina García-De la Peña

NICHE SEGREGATION WITHIN A DUNE LIZARD COMMUNITY IN COAHUILA, MEXICO

Abstract We studied niche segregation among 3 syntopic lizards, Uta stejnegeri, Uma exsul, and Aspidoscelis marmorata, in the sand dunes of Viesca, Coahuila, Mexico. In 2004, we analyzed both microhabitat and substrate niches during a warm season and a cold season. Niche breadth and overlap were calculated, and a selection index was used. Each lizard species selected microhabitats that focused on a single perennial plant species and a specific range of sand compactness. Uta stejnegeri was highly associated with the perennial Suaeda nigrescens and highly compacted sand. Uma exsul was associated with sites with deep, loosely compacted sand and Larrea tridentata. Aspidoscelis marmorata was associated with the occurrence of Prosopis glandulosa and moderately compacted sand. Associations described here could help to develop a future conservation and management program for these sand dunes, where the endemic U. exsul and other species are protected.

Phylogenetic Constraints Do Not Block Food Chemical Discrimination in the Omnivorous Phrynosomatid Lizard Uma exsul

Abstract In lizards identification of food using chemical cues allows active foragers to locate hidden prey and omnivores and herbivores to identify palatable plant food, but ambush foragers identify food visually rather than chemically. Omnivores and herbivores derived from ambushing ancestors discriminate food chemicals from control substances. The only known exception is the omnivorous phrynosomatid lizard Sceloporus poinsettii, which lacks food chemical discrimination and which might have been constrained from evolving it by scarcity of chemoreceptors. We studied food chemical discrimination by the phrynosomatid Uma exsul, an omnivore whose diet is 25% plant by volume. In 60 s trials in which chemical cues from mealworms, romaine lettuce, cologne, and water were presented on cotton swabs, lizards responded more strongly to plant and animal chemicals than control stimuli. Food chemical discrimination by Uma exsul strengthens evidence that plant chemical discrimination evolves in tandem with plant diet and prey chemical discrimination also appears in omnivores or herbivores derived from ambush foragers. Confirmation of food chemical discrimination in U. exsul vitiates the evolutionary constraint hypothesis for S. poinsettii. That lizards tongue-flicked and bit infrequently, yet discriminated, is unusual, suggesting that lingually mediated plant chemical discrimination may have evolved recently, few tongue-flicks are needed to evaluate nutritive properties of plant foods, or plant chemical discrimination is an adaptively unimportant epiphenomenon of plant consumption. Because they do not search actively for prey or tongue-flick before attacking, phrynosomatids presumably evolve prey chemical discrimination by genetic correlation with plant chemical discrimination.

Eutrombicula alfreddugesi (Acari: Trombiculidae): New Host Records from Four Species of Lizards in the Sierra de Jimulco, Coahuila, Mexico

Abstract I collected larvae of Eutrombicula alfreddugesi for the first time parasitizing Gerrhonotus infernalis, Sceloporus poinsetti, S. jarrovii, and S. grammicus as new host records for Coahuila, Mexico. Lizards were collected in the submontane scrub of the Sierra de Jimulco, Coahuila, Mexico. In G. infernalis, there was a large number of mites in small groups, primarily along the flanks protected by the granular fold. All species of Sceloporus had mites in the neck region grouped behind the eardrums and protected by lateral gular folds. Type of vegetation and available substrates in this part of the Sierra de Jimulco create microhabitats that can support this mite.I collected larvae of Eutrombicula alfreddugesi for the first time parasitizing Gerrhonotus infernalis, Sceloporus poinsetti, S. jarrovii, and S. grammicus as new host records for Coahuila, Mexico. Lizards were collected in the submontane scrub of the Sierra de Jimulco, Coahuila, Mexico. In G. infernalis, there was a large number of mites in small groups, primarily along the flanks protected by the granular fold. All species of Sceloporus had mites in the neck region grouped behind the eardrums and protected by lateral gular folds. Type of vegetation and available substrates in this part of the Sierra de Jimulco create microhabitats that can support this mite. RESUMEN—Registré por primera vez larvas de Eutrombicula alfreddugesi parasitando a Gerrhonotus infernalis, Sceloporus poinsetti, S. jarrovii y S. grammicus como nuevos registros de hospederos para el estado de Coahuila, México. Las lagartijas fueron colectadas en el matorral submontañoso de la Sierra de Jimulco, Coahuila, México. En G. infernalis se registró una gran cantidad de ácaros en pequeñas agrupaciones, principalmente a lo largo de los flancos protegidos por el pliegue granular. Todas las especies de Sceloporus portaban ácaros en la región del cuello, agrupados detrás de los tı́mpanos y protegidos por los pliegues gulares laterales. El tipo de vegetación y los sustratos disponibles en esta parte de la Sierra de Jimulco crean microhábitats que pueden favorecer la presencia de este ácaro. Understanding the distribution and host relationships of mites includes their potential importance as disease vectors in humans. Eutrombicula alfreddugesi is an ectoparasitic chigger mite of a large number of amphibians, reptiles, birds, and mammals (Philips, 2000; de Carvalho et al., 2006; Lareschi, 2006; Paredes-León et al., 2006, 2008; Rubio and Simonetti, 2009). This species has medical importance because it causes trombidiasis (trombiculiasis) in humans, a skin disease that produces a characteristic itching and inflammation that is particularly frequent in children (De la Cruz and Abreu, 1986; Potts, 2001). This chigger mite has been reported throughout the Western Hemisphere from southern Canada to Argentina and the Caribbean Islands (Daniel and Stekol’nikov, 2004). There have been records of E. alfreddugesi from 30 states in Mexico (Hoffmann, 1990; Paredes-León et al., 2008). In May 2009, I captured 14 lizards (five Gerrhonotus infernalis, three Sceloporus poinsetti, three Sceloporus jarrovii, and three Sceloporus grammicus) from the Sierra de Jimulco, Municipality of Torreón, Coahuila, Mexico (25u119370N, 103u189410W). Dominant vegetation here was submontane scrub (1,700–3,100 m elevation; Rhus virens, Mortonia greggi, Juniperus flacida, Quercus, Fraxinus, and Arbutus) on limestone substrate. Lizards were captured with a noose or by hand and were transported in fabric bags to the Escuela Superior de Biologı́a, Universidad Juárez del Estado de Durango. All individuals of the four species of lizards had red mites. Mites were removed in the laboratory using wetted (ethanol) cotton swabs. The red color of the mites facilitated counting them on the surface of the cotton with a magnifying glass and then collecting them in 70% ethanol for later taxonomic identification. Lizards were deposited in the Museo de Zoologı́a Alfonso L. Herrera, Universidad Nacional Autónoma de México, and mites were deposited in the Vertebrate Laboratory of the Escuela Superior de Biologı́a, Universidad Juárez del Estado de Durango. Gerrhonotus infernalis had a large number of mites in small clusters from the sides of the neck along the length of the flanks, protected in the granular fold that is characteristic of Anguidae THE SOUTHWESTERN NATURALIST 56(1):131–133 March 2011 Notes 131

VARIATION IN HOME RANGE OF THE SIDE-BLOTCHED LIZARD, UTA STEJNEGERI, IN COAHUILA, MEXICO

Abstract We studied seasonal variation in size and fidelity of home range in a population of eastern side-blotched lizards, Uta stejnegeri, in southern Coahuila, Mexico. Field work was carried out during the active seasons of 2002–2004. Home ranges during breeding and non-breeding seasons were larger for males than females and were reduced in both sexes during non-breeding months (autumn). There was greater intersexual overlap of home range during summer and less in autumn. Intrasexually, males had more overlap in home range than females (particularly during summer), which could be related to their large home ranges during that season. Fidelity to home range from one season to the next in a given year was similar in males and females. Although males had greater length and mass than females, neither measure correlated with size of home range. Density of adult lizards was negatively correlated with size of home range during the reproductive period. During non-reproductive months, density of all age classes combined was negatively correlated with size of home range. Our results indicate that home range sizes of U. stejnegeri vary considerably over the year and diverse factors are involved.

Spatial Segregation of Microhabitats Within a Community of Lizards in Médanos de Samalayuca, Chihuahua, Mexico

Abstract We described seasonal microhabitats of the lizards Uta stansburiana, Phrynosoma modestum, and Aspidoscelis tigris in the sand dunes of Medanos de Samalayuca, Chihuahua, Mexico. Uta stansburiana and A. tigris used many resources in common and frequently were observed under honey mesquites Prosopis glandulosa, the most common and largest shrub on our study site. In contrast, P. modestum was more common in bare areas. Uta stansburiana and A. tigris showed moderate to high overlap in vegetative cover and compaction of substrate. With respect to Uta stansburiana and A. tigris, P. modestum showed low-to-moderate overlap in microhabitats.