Denton Jonathan S, Beebee Trevor J C
School of Biology, University of Sussex, Falmer, BN1 9QG, Brighton, Sussex, UK.
Oecologia. 1994 Apr;97(3):390-398. doi: 10.1007/BF00317330.
Two congeneric anurans with highly overlapping geographical ranges, Bufo bufo and B. calamita, were investigated with respect to isolating mechanisms during the terrestrial phase of life in the three habitat types in which both species occur in Britain. Marked spatial niche separations were observed in all three habitats (coastal dunes, upper saltmarshes and lowland heaths). B. bufo was associated with complex, dense vegetation structures and had a relatively wide niche, while B. calamita had a narrower niche and occurred mostly on open, poorly-vegetated ground. Food niche overlap was high at all three study sites. Animals translocated into atypical habitats returned to their preferred type whenever possible, and suffered increased mortality or loss of condition if prevented from doing so. B. calamita operated at significantly higher body temperatures (by an average of 1.4° C) than B. bufo when hunting at night. Experiments in outdoor vivaria indicated that B. calamita survived in open habitats because individuals escaped desiccation in daytime by burrowing into the substrate, whereas B. bufo lacked this behaviour and perished on the inhospitable surface. By contrast, B. calamita individuals lost mass and became hyperactive in densely-vegetated conditions because their hunting efficiency was selectively reduced relative to that of B. bufo. Taken together, the data indicated that spatial niche separation between these species during the terrestrial phase of life was dictated primarily by behavioural and physiological factors, and not by competition.
对两种地理分布范围高度重叠的同属无尾目动物，即普通蟾蜍（Bufo bufo）和绿蟾蜍（B. calamita），在英国这两种物种均有分布的三种栖息地类型中，研究了其在陆生阶段的隔离机制。在所有三种栖息地（沿海沙丘、上部盐沼和低地石南荒原）均观察到明显的空间生态位分离。普通蟾蜍与复杂、茂密的植被结构相关联，具有相对较宽的生态位，而绿蟾蜍的生态位较窄，主要出现在开阔、植被稀疏的地面。在所有三个研究地点，食物生态位重叠度都很高。被转移到非典型栖息地的动物只要有可能就会回到它们喜欢的栖息地类型，如果被阻止则会死亡率增加或身体状况下降。绿蟾蜍在夜间捕猎时的体温显著高于普通蟾蜍（平均高1.4摄氏度）。室外饲养箱实验表明，绿蟾蜍能在开阔栖息地生存是因为个体在白天通过挖掘进入基质来避免脱水，而普通蟾蜍缺乏这种行为，会在不适宜的表面死亡。相比之下，绿蟾蜍个体在植被茂密的环境中体重减轻且变得多动，因为相对于普通蟾蜍，它们的捕猎效率被选择性降低。综合来看，数据表明这两种物种在陆生阶段的空间生态位分离主要由行为和生理因素决定，而非竞争。
