Anuran Habitat Associations in the Northern Chihuahuan Desert, USA
Understanding amphibian habitat associations allows us to assess the impacts of environmental change on amphibian populations. We studied the habitat associations of five anurans in the Chihuahuan Desert of southern New Mexico, USA. We used amphibian call surveys at 36 ephemeral water bodies and recorded an index of abundance for each species. We used GIS to identify vegetation communities (e.g., creosote bush, grassland, mesquite) within a buffer zone around each water site. We used ordinal logistic regression, Akaike's information criterion (AICc), and canonical correspondence analysis to elucidate relationships between an index of anuran abundance and habitat variables. Creosote bush, mesquite, and grasses dominate the landscape in our study region. We detected Anaxyrus debilis (Green Toad) and Spea multiplicata (New Mexico Spadefoot Toad) most frequently (>70% of water bodies observed). Anaxyrus cognatus (Great Plains Toad), Scaphiopus couchii (Couch's Spadefoot Toad), and Spea bombifrons (Plains Spadefoot Toad) were detected at about half of water bodies studied. Anaxyrus cognatus, Spea bombifrons, and Sp. multiplicata tended to co-occur at breeding sites. Anaxyrus cognatus and Sp. bombifrons were more common in mesquite habitat. Succulent desert scrub, though not common, seemed to affect Sc. couchii positively and A. debilis negatively. Spea multiplicata was more generalistic and did not show strong habitat associations. We did not find evidence that shrub encroachment has had negative impacts on the amphibian community in our study system and may even have had positive effects on anurans, especially A. cognatus and Sp. bombifrons.Abstract
Map of study area. Sampling sites where toads were calling are marked as circles. White circles are natural ephemeral playa lakes and gray circles are earthen stock tanks (built for livestock). Las Cruces is a city and Jornada, Sleeping Lady Hills, and Hatch refer to our three regional field locations.
Canonical correspondence analysis relating toad call indices to habitat parameters (N = 33). Species (triangles) that are located in the same direction as a habitat variable (arrows) correspond positively, species located in the opposite direction correspond negatively. A right angle between species and habitat direction means no correspondence. The longer the arrow, the higher the observed variability of that parameter in the field. Solid arrows show habitat parameters that significantly influenced species occurrence (P < 0.05). The further the species are from the center point, the stronger the correspondence. “Rich” stands for anuran species richness.
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