Newman R A
Department of Biology, University of Pennsylvania, 19104, Philadelphia, PA, USA.
Oecologia. 1987 Jan;71(2):301-307. doi: 10.1007/BF00377299.
The effects of density on growth and development of Scaphiopus couchi tadpoles in desert ponds were investigated, and sources of mortality over a three-year period were documented. In 16 of the 82 ponds monitored, predation was the principal cause of death, demonstrating that tadpoles in desert ponds may be exposed to high levels of predation, although the overall importance of predation is less here than in more mesic areas. Desiccation was the primary cause of mortality in 49 ponds. Growth and development were extremely slow in most high density ponds and as a result most tadpoles were unable to metamorphose before ponds dried. Only 8 ponds produced metamorphs, and mortality was high even in these. Food-supplementation resulted in some metamorphosis in high density ponds, although the effect was diminished by the extreme crowding in most ponds. In low density ponds, S. couchi tadpoles can develop very quickly and metamorphose. High mortality due to desiccation is largely a consequence of high density: tadpoles rarely completed development in high density ponds, regardless of pond duration.
研究了密度对沙漠池塘中美西锄足蟾蝌蚪生长和发育的影响，并记录了三年期间的死亡原因。在监测的82个池塘中的16个中，捕食是主要死亡原因，这表明沙漠池塘中的蝌蚪可能面临高水平的捕食，尽管捕食在这里的总体重要性低于在更多湿润地区。干涸是49个池塘中死亡的主要原因。在大多数高密度池塘中，生长和发育极其缓慢，因此大多数蝌蚪在池塘干涸之前无法变态。只有8个池塘产生了变态个体，即使在这些池塘中死亡率也很高。食物补充在高密度池塘中导致了一些变态，尽管在大多数池塘中由于极度拥挤，这种效果有所减弱。在低密度池塘中，美西锄足蟾蝌蚪可以快速发育并变态。由于干涸导致的高死亡率在很大程度上是高密度的结果：无论池塘持续时间如何，蝌蚪在高密度池塘中很少完成发育。
