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Centro de Investigaciones Biológicas del Noroeste (CIBNOR) 2003

Abundancia, distribución y nicho espacial de las lagartijas diurnas de Isla Coronados, Baja California Sur, México

Venegas Barrera, Crystian Sadiel

Titre : Abundancia, distribución y nicho espacial de las lagartijas diurnas de Isla Coronados, Baja California Sur, México

Auteur : Venegas Barrera, Crystian Sadiel

Etablissement de soutenance : Centro de Investigaciones Biológicas del Noroeste (CIBNOR)

Grade : Maestría en Ciencias en el Uso, Manejo y Preservación de los Recursos Naturales 2003

In basic and applied ecology it is useful to identify and associate the spatial and temporal patterns of species with their abundance, distribution and relocate of resources. However, few studies have explored this association through time. To do so, we used an arid island’s diurnal lizards as biological models because their distribution probably represents the development of interspecific relationships. The present study was developed in Coronados island, located in the protected natural area “Parque Nacional Bahía de Loreto", east from Loreto, Baja California Sur, México. This is one of the most diverse islands in the Gulf of California respect to diurnal lizards, with ten species, four are endemic of the country (Sauromalus slevini, Petrosaurus repens, Sceloporus zosteromus and Urosaurus nigricaudus), one is threatened (Callisaurus draconoides) and five have wide distribution (Dipsosaurus dorsalis, Sceloporus orcutti, Uta stansburiana, Cnemidophorus hyperytrhrus and C. tigris). The importance of this study resides on that Coronados is one of the most tourist-visited islands in the “Parque Nacional Bahía de Loreto”. We determined the diurnal lizards’ temporary and spatial changes in abundance and geographical distribution, as well as their relationship with their spatial niche. We delimited and characterized the homogenous areas (landscape units) for the soil, rock and vegetation observed in field taking like reference the air picture. From June to December 2001 and from April to June 2002, we visited the island once a month during four days and conducted walking transects. Each transect was carried out walking slowly from 0800 to 1500 and from 1600 to 1900 (local time). The abundance was evaluate using three discreet statistical distributions that represented a gradient in the aggregation of the individuals. The distribution was obtained by the number of landscape units used, as well as the suitability maps of the diurnal lizards, using the ecological factors of niche analysis (EFNA). To identify the spatial and temporal niche it was used two analysis : 1) the traditional in bibliography (niche breadth and overlap) ; 2) niche analysis or outlaying mean index (OMI) that is used in the multidimensional study of the breadth of the species. We found that the species presented temporal and spatial variations in abundance, aggregation and niche. A gradient of abundance, distribution and niche among species was found, in which the rare species with low aggregations and restricted distributions were associated to specific environmental characteristics (like C. draconoides), whereas the abundant species with high spatial aggregations and wide distributions were generalists (as U. stansburiana). The landscape units with a low diversity index were associated with high percentages of clear soils, low percentages of rocks and sandy soils, while the landscape units with a high diversity index were related to were clayed or slime soils, intermediate percentages of rock (20-100 cm) and vegetation. All the species presented a separation in at least one of the main axes of the niche. We conclude that the temporal and spatial changes in the abundance and distribution of the Coronados’ diurnal lizards are associated with the number of available environmental resources that satisfy their niche requirement

Mots Clés : Lagartijas diurnas ; análisis multivariados ; abundancia ; distribución ; nicho


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