THE ADAPTIVE SIGNIFICANCE OF AN ENVIRONMENTALLY-CUED DEVELOPMENTAL SWITCH IN AN ANURAN TADPOLE
THE ADAPTIVE SIGNIFICANCE OF AN ENVIRONMENTALLY-CUED DEVELOPMENTAL SWITCH IN AN ANURAN TADPOLE
复制标题
DOI：
10.1007/bf00317349
复制
发表时间：
1990-01-01
期刊：
影响因子：
2.7
通讯作者：
PFENNIG, D
中科院分区：
文献类型：
--
作者：
PFENNIG, D
本研究调查了铲足蟾蜍（Scaphiopus multiplicatus）自然种群中发生的双峰分布、环境引起的变异的直接基础。大多数种群中的大多数个体都是小型的、发育缓慢的杂食动物。在其中一些相同的种群中，不同数量的个体出现为大型、快速发育的食肉动物形态（Pfennig 1989）。对 37 个不同天然池塘的普查显示，发育较快的食肉动物变种的频率与神仙虾密度（它们的主要猎物）和池塘干燥率呈显着正相关。通过同时改变两种饲料成分和人工池中的池塘干燥方式，我发现只有神仙虾的密度显着影响食肉动物的比例。单独的实验表明，蝌蚪发展出食肉动物形态的程度与虾的密度相关，并且形态的确定取决于虾的摄入，而不仅仅是虾的存在。如果摄入了一定数量的虾，蝌蚪就会发育成肉食动物；如果没有，蝌蚪就会默认发育成杂食动物。因此，单一线索——虾的摄入——触发了替代的个体发育轨迹。利用虾的密度来诱导形态分化，使蝌蚪能够适应性地对其环境作出反应，因为虾在高度短暂的池塘中最为丰富，那里生长较快的食肉动物受到青睐。
This study investigated the proximate basis of bimodally-distributed, environmentally-induced variation that occurs in natural populations of spade-foot toad tadpoles (Scaphiopus multiplicatus). Most individuals in most populations occur as a small, slowly-developing omnivore morph. In some of these same populations, a varying number of individuals occur as a large, rapidly-developing carnivore morph (Pfennig 1989). Censuses of 37 different natural ponds revealed that the frequency of the faster-developing carnivore morph correlated significantly positively with fairy shrimp density (their chief prey) and pond drying rate. By simultaneously varying two diets components and pond drying regime in artificial pools I found that only fairy shrimp density significantly affected the proportion of carnivores. Separate experiments estasblished that the extent to which tadpoles developed the carnivore morphology correlated with shrimp density, and that morph determination depended on the ingestion of shrimp, not simply their presence. If a critical number of shrimp were ingested, the tadpole developed into a carnivore; if not, the tadpole developed by default into an omnivore. Thus a single cue-shrimp ingestion-triggers alternative ontogenetic trajectories. Using shrimp density to induce morph differentiation enables tadpoles to respond to their environment adaptively as shrimp are most abundant in highly ephemeral ponds, where the faster developing carnivores are favored.