Loren M. Smith

Although amphibians are the dominant vertebrate inhabiting playa wetlands during spring and summer in the Southern Great Plains, little is known about their diet and role in playa trophic structure. Because new metamorphs are more numerous than other terrestrial life stages of amphibians, we describe the diets of recently (95%); therefore, we also examined this influence on diets of Great Plains toad metamorphs. Diets of all 3 species were dominated by coleopteran taxa, and diversity of prey taxa did not vary among species. Amount of specific prey consumed varied among species, with Great Plains toads preying more on scarab beetles and formicid ants than New Mexico spadefoots and tiger salamanders. New Mexico spadefoot metamorphs consumed more chrysomelid and elaterid beetles than tiger salama... Resumen Los anfibios son los vertebrados más abundantes durante la primavera y el verano en los lagos playa de las Grandes Planicies Sureñas. Sin embargo, poca información existe sobre su dieta y posición en la estructura trófica. Porque los recién metamorfoseados son más abundantes que los otros estadios terrestres de anfibios, describimos las dietas de animales recientemente metamorfoseados (95%), por lo que también examinamos el efecto de este factor sobre las dietas de metamorfoseados de B. cognatus. La presa principal de las tres especies fue coleóptera y no hubo diferencias entre especies en la diversidad de presas. La cantidad de presas específicas consumidas sí varió. Bufo cognatus consumió más escarabajos escárabos y hormigas formí...

There are 25,000–30,000 playa wetlands in the intensively cultivated Southern Great Plains of the United States. Knowledge of area and watershed influences on wetland flora are needed to guide their conservation. We surveyed plant‐community composition in 224 playas over 360,000 km ² and examined the relationships of species richness and diversity ( Shannon's) to playa area and watershed disturbance. The relationship of increasing species diversity to increasing area is most often hypothesized to be associated with an increasing number of habitats and/or larger populations as area increases. Watershed disturbance ( perennial grassland vs. annual cropland) was included to determine its relationship to floral diversity and bioinvasion by exotic species. For all (terrestrial and wetland) plant species and all playas, there were only marginal relationships ( r ² < 0.1) between area and richness and diversity. Analyses supported the hypothesis that the number of habitats affects playa plant diversity because number of habitats changed little as playa area increased. Tests on only wetland plant species suggested stronger ( r ² ≅ 0.2) relationships between richness and area. This relationship also was not likely related to increased population size, because large playas remain flooded longer than small playas, and therefore wetland plant species have a greater opportunity to become established. Finally, playas with cropland watersheds had more ( p < 0.05) exotic species, higher diversity, and fewer perennial species than playas with grassland watersheds. Because watershed cultivation has altered playa hydroperiod and increased frequency of disturbance, playas are associated with a flora dominated more by annuals and exotics. Conservation efforts aimed at preserving playa wetland plant diversity and native communities should focus not only on the area of the wetland but also on the condition of its watershed.