欧洲蟾蜍。
资料来源: Bert Willaert

据2月5日的《科学》杂志报道说，新的研究也许能够解释蟾蜍为什么能够在仅仅5500万年之中就能够在大部分的陆地生根繁殖。 蟾蜍科中已知的品种有500个左右，它们在全世界占据着多种不同的栖息地。 有些蟾蜍（如五彩蟾蜍）存在于小面积的地区，它们非常脆弱；另外有些蟾蜍（如甘蔗蟾蜍）则以它们的适应能力及一种 异常快的速度来扩大其活动范围而著称。

Ines Van Bocxlaer及其一个国际性团队的同僚对与蟾蜍地理分布范围有关的不同特性的进化史进行了重构，并发现了7种可能使蟾蜍能够扩大其活动范围的特性。 文章的作者报告说，比如，那些无需依赖永久的有水环境或潮湿空气的成年蟾蜍会有较大的分布范围。 那些能够在不同的水体中产卵的蟾蜍，那些幼体能够从环境中而非从其母体摄取食物的蟾蜍，以及那些产卵数较多的蟾蜍都可能会有较为广泛的分布。

文章的作者提出，大多数的原种蟾蜍都累积有这些特性，从而建立了一种可使该群体扩大和发散的“分布区扩大的表型”。 除了能够解释这些物种在远古时期的发散之外，这一研究的框架可帮助解释当代的扩散性物种（如甘蔗蟾蜍）的进化背景。

原始出处：

Science 5 February 2010: DOI: 10.1126/science.1181707

Gradual Adaptation Toward a Range-Expansion Phenotype Initiated the Global Radiation of Toads

Ines Van Bocxlaer,1 Simon P. Loader,2 Kim Roelants,1 S. D. Biju,3 Michele Menegon,4 Franky Bossuyt1,*

Recent studies have identified range expansion as a potential driver of speciation. Yet it remains poorly understood how, under identical extrinsic settings, differential tendencies for geographic movement of taxa originate and subsequently affect diversification. We identified multiple traits that predict large distributional ranges in extant species of toads (Bufonidae) and used statistical methods to define and phylogenetically reconstruct an optimal range-expansion phenotype. Our results indicate that lineage-specific range-shifting abilities increased through an accumulation of adaptive traits that culminated in such a phenotype. This initiated the episode of global colonization and triggered the major radiation of toads. Evolution toward a range-expansion phenotype might be crucial to understanding both ancient widespread radiations and the evolutionary background of contemporary invasive species such as the cane toad.

1 Biology Department, Amphibian Evolution Lab, Unit of Ecology and Systematics, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium.
2 Department of Environmental Sciences, Section of Biogeography, University of Basel, 4056 Basel, Switzerland.
3 Systematics Lab, Centre for Environmental Management of Degraded Ecosystems (CEMDE), School of Environmental Studies, University of Delhi, Delhi 110 007, India.
4 Sezione di Zoologia dei Vertebrati, Museo Tridentino di Scienze Naturali, Via Calepina 14, I–38100 Trento, Italy.