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Rythmes Journaliers d'activite et partage de ressources dans une communaute de lezards du desert de Sonora, Mexique
Abstract
The diurnal activity rhythms of the five more numerous species in a lizard community of the Sonoran desert were studied in October 1982 and June 1983, near El Pinacate, Mexico.
The diurnal rhythms of the five species were very similar, but varied extensively from summer to autumn. These rhythms were obviously dependent on the thermal constraints of the environment, and these constraints were so strong that they led to an almost identical activity pattern in all species.
... lización que muestran varias de las especies a nivel de micro-habitat, es un aspecto ampliamente conocido en general para las lagartijas (Pianka, 1966Pianka, , 1986). Sin embargo, tales especializaciones no son necesariamente un resultado inducido competitivamente , como ya ha sido previamente discutido (Barbault y Maury, 1981; Ortega et. al., 1982 Ortega et. al., ,1986 Barbault et. al. 1985). De hecho, muchas especies de lagartijas dependen estrechamente de su adaptación a determinado tipo de substrato tanto para escapar de los posibles depredadores, como para efectuar una eficiente termoregulación y para defender con txito su territorio. Desde este punto de vista la especialización a un substrato pue ...
... Differences in year to year diet, using more precise taxonomic levels of approach, have not usually been analysed. The present work examines the trophic aspects of a desert lizard guild, whose selection of rnicrohabitat and temporal dephasing have already been studied (Ortega et al., 1986;González-Romero et al., 1989). The trophic aspects of organization, based on a comparative analysis of the diet of the species, is examined. ...
The food niche relationships of a lizard community of an arid zone in the State ofSonora, NW Mexico, were studied during 1982, 1983 and 1984. The species with highly specialized diets showed little variation in food habits during those years, while the opposite occurred with more eclectic predators. The expected correlation between the size of the predator and the size of its prey can also be biased by food specialization. Food niche overlaps, based on analysis of the volume and the taxonomic status of the prey at a family level, were persistently low. The role that food niche partitioning could play in determining the organization of this lizard guild is discussed.
In 2002, daily and seasonal activity patterns of the lizards Uta stejnegeri, Uma exsul, and Aspidoscelis marmorata were evaluated in a dune habitat in the southwestern portion of Coahuila, Mexico. Methods included surveying a 500 m transect once per hour between 0700 and 1900 for 7 days each season during the spring, summer and fall. The number of active lizards, air and substrate temperatures, and relative humidity were recorded. A standardized Levins Index and Pianka’s method were used to measure temporal niche breadth and overlap, respectively. In each of the 3 seasons, U. stejnegeri was active earlier than U. exsul, and U. exsul was active before A. marmorata. The 3 species showed a bimodal activity pattern during spring and summer, and unimodal in fall. Aspidoscelis marmorata showed the smallest niche breadth in the 3 seasons. For each species, preferred body temperature and environmental temperature seem to dictate activity patterns of this lizard guild at Viesca.
This chapter presents an analysis and summary of the herpetology of the dry borderlands of southwestern
Arizona and northwestern Sonora, encompassing the hottest, driest desert region of North America and its transition to the rich Arizona Upland province of the Sonoran Desert. It is based on my data and experience added to a survey of museum voucher localities and literature pertaining to the Sonoran and Mojave deserts in and surrounding this region. The dry borderlands supports a herpetofauna of 70 verified species, including 9 verified only from the big rivers.
The analysis highlights three major desert herpetological formations in the dry borderlands. (1) The Arizona Upland assemblage, thornscrub associated and mostly to the east and north, is present in important part. It shows a marked transition to the true desert herpetofauna, which is represented by (2) the combined Lower Colorado Valley- Mojave Desert herpetofauna. This true desert herpetofauna, which is characteristic of the dry borderlands, contains (3) a distinctive sand associated herpetofauna in its hyperthermic and hyper-arid portion, the Gran Desierto.
The Lower Colorado Valley herpetofauna is not markedly distinct from that of the Mojave Desert: the principal true desert species are centered over the combined area of these two recognized desert areas. This finding points toward a concept of the Colorado-Mojave Desert as a valid, arid entity, with a blazing subtropical core that in hot dry times drives its less tolerant species toward the periphery or out to their primary distributional centers. The dry borderlands area is essential to the survival of the biota most central to it- the true desert biota of North America's most arid region.
The spatial structure of a desert lizard community located in the state of Sonora, N.E. Mexico, was studied in October 1982 and June 1983. The community is composed of 17 species, and we analyzed the habitat partitioning and microhabitat utilization of 12 species recorded along two transects. We found that habitat and microhabitat selection plays a determining role in organizing this lizard community and its ecological meaning is discussed.
In 1988 and 1989 we investigated the ecology of a reptile community inhabiting a suburban area altered by human activity. Recent changes in and partial destruction of diversified habitats have been directly involved in the faunistic paucity of all the area, where only three lizard and three snake species have been found, but only four of which are really common. The known thermal preference of every species has been confirmed, and some differences among taxa have been observed in lizard sex‐ratio and snake biometry. Available and suitable habitats are discontinuous in the area, which probably explains the different observed distribution of the reptile community.
The community is composed of seven species, including four Sceloporus. Analysis of microhabitat and substrate utilization by al1 the species in two main habitats shows that species are not specialized according to habitat but are specialized to microhabitat-substrate. Spatial niche-overlap values are very low for al1 paired species. The deter-mining role of microhabitat selection in organizing this lizard community and its general ecological meanings are discussed. KEY-WORDS: Habitut partitioning -Subsrrore selecrion -Community -Mé.xicu -Sierra Madre Occiden~ol-Lizords -Sceloporus.
Food niche relationships among four sympatric Sceloporus species were studied in the Sierra Madre Occidental, N.E. Mexico. Although some very high food-niche overlap values were observed, this does not prove that interspecific competition is currently important in organizing this lizard assemblage. Moreover, explaining habitat segregation among the coexisting species as an ecological result of interspecific competitive pressure is unlikely: the overall ecology and behaviour of these species is too much dependent on their microhabitat or substrate specialization to allow such an exclusive interpretation. Thus, this community is probably not mainly organized by species interactions but rather through the specific ecological needs of each species.
Niche relationships among 11 diurnal lizard species were studied for 3 years. The community appeared to be subdivided spatially into different subsets of only four to six species. Coexisting species of each subgroup were separated further by differential utilization of microhabitats. In late spring and early summer, when food shortage is likely, dietary overlaps between syntopic species were generally low but increased broadly after the rains, when food became plentiful. Because of the high similarity in prey-size utilization among large and medium species, effects of prey selection according to size were generally slight except for very different-sized species. Overlap in the three-dimensional resource space was high between Cnemidophorus scalaris and C. tigris, but close observation of the ecology of the two populations showed many small differences between them. We suggest that the very diversified ecological opportunism of C. scalaris allows it to coexist with C. tigris in a very heterogeneous ecosystem. Several hypotheses are discussed to explain the ecological determinism of resource partitioning within such a community.
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