Magnusson William E, Hero Jean-Marc
Instituto National de Pesquisas da Amazonia (INPA), Alameda, Cosme Ferreira 1756. Aleixo, 69083, Manaus, AM, Brasil.
Division of Australian Environmental Studies, Griffith University, Nathan, 4111, Brisbane, Queensland, Australia.
Oecologia. 1991 May;86(3):310-318. doi: 10.1007/BF00317595.
Terrestrial oviposition with free-living aquatic larvae is a common reproductive mode used by amphibians within the central Amazonian rainforest. We investigated the factors presently associated with diversity of microhabitats (waterbodies) that may be maintaining the diversity of reproductive modes. In particular, desiccation, predation by fish, competition with other anurans and water quality were examined in 11 waterbodies as possible forces leading to the evolution of terrestrial oviposition. Predation experiments demonstrated that fish generally do not eat anuran eggs, and that predacious tadpoles and dytiscid beetle larvae are voracious predators of anuran eggs. The percentage of species with terrestrial oviposition was only weakly correlated with the occurrence of pond drying, pH and oxygen concentration, suggesting that anurans in this tropical community are able to use the range of water quality available for egg development. There was a tendency for terrestrial oviposition to be associated with the number of species of tadpoles using the waterbody, but we consider this to be spurious as there was no obvious competitive mechanism that could result in this relationship. The percentage of species with terrestrial oviposition was significantly positively related to our index of egg predation pressure, and negatively related to our index of fish biomass. Egg predation pressure was also negatively related to the index of fish biomass. These results allow us to discount as improbable the hypothesis that predation by fish on anuran eggs was an important selective pressure leading to terrestrial oviposition in this community. The strong positive relationship between terrestrial oviposition and our index of egg predation pressure indicates that these predators have exerted, and are exerting, a significant selective pressure for terrestrial oviposition. The strong negative relationship between the occurrence of fish and the egg predators suggests the surprising conclusion that the presence of fish actually protects aquatic anuran eggs from predation in this tropical system, and allows aquatic oviposition to dominate only in those waterbodies with moderate to high densities of fish. Our results suggest that terrestrial oviposition is a "fixed predator avoidance" trait.
具有自由生活水生幼体的陆地产卵是亚马逊雨林中部两栖动物常见的繁殖模式。我们调查了目前与微生境（水体）多样性相关的因素，这些因素可能维持着繁殖模式的多样性。特别是，在11个水体中研究了干燥、鱼类捕食、与其他无尾两栖类的竞争以及水质，将其作为导致陆地产卵进化的可能因素。捕食实验表明，鱼类通常不吃无尾两栖类的卵，而肉食性蝌蚪和龙虱幼虫是无尾两栖类卵的贪婪捕食者。具有陆地产卵的物种百分比与池塘干涸、pH值和氧气浓度的发生仅呈弱相关，这表明该热带群落中的无尾两栖类能够利用可用于卵发育的水质范围。陆地产卵倾向于与使用该水体的蝌蚪物种数量相关，但我们认为这是虚假的，因为没有明显的竞争机制能导致这种关系。具有陆地产卵的物种百分比与我们的卵捕食压力指数显著正相关，与我们的鱼类生物量指数负相关。卵捕食压力也与鱼类生物量指数负相关。这些结果使我们认为，鱼类对无尾两栖类卵的捕食是导致该群落陆地产卵的重要选择压力这一假设不太可能成立。陆地产卵与我们的卵捕食压力指数之间的强正相关表明，这些捕食者已经并正在对陆地产卵施加显著的选择压力。鱼类的出现与卵捕食者之间的强负相关表明了一个惊人的结论，即在这个热带系统中，鱼类的存在实际上保护了水生无尾两栖类的卵免受捕食，并使得水生产卵仅在鱼类密度适中至高的水体中占主导地位。我们的结果表明，陆地产卵是一种“固定的捕食者回避”特征。
