在与有毒的猎物粗皮蝾螈进行的“军备竞赛”中，西部袜带蛇成为了最后的赢家（如图）。
据美国《科学》杂志在线报道，随着时间的推移，蝾螈逐渐进化出了毒性—— 一只蝾螈足以毒死几个成年人，而蛇对这种毒性的抵抗能力则也变得越来越强。将近1/3的美国西部袜带蛇能够承受蝾螈的毒性。这种保护功能主要依赖于一个与离子通道有关的基因产生的突变，从而防止该通道因毒素的作用而关闭，并且由此产生了一个蝾螈难以企及的强大的免疫系统。研究人员在最近的《科学公共图书馆·生物学》（PLoS Biology）网络版上报告了这一研究成果。（来源：科学时报 群芳）
生物谷推荐原始出处：
（PLoS Biology），doi:10.1371/journal.pbio.0060060，Charles T. Hanifin, Edmund D. Brodie Jr., Edmund D. Brodie III
Phenotypic Mismatches Reveal Escape from Arms-Race Coevolution
Charles T. Hanifin1¤*, Edmund D. Brodie Jr.1, Edmund D. Brodie III2
1 Department of Biology, Utah State University, Logan, Utah, United States of America, 2 Department of Biology, University of Virginia, Charlottesville, Virginia, United States of America
Because coevolution takes place across a broad scale of time and space, it is virtually impossible to understand its dynamics and trajectories by studying a single pair of interacting populations at one time. Comparing populations across a range of an interaction, especially for long-lived species, can provide insight into these features of coevolution by sampling across a diverse set of conditions and histories. We used measures of prey traits (tetrodotoxin toxicity in newts) and predator traits (tetrodotoxin resistance of snakes) to assess the degree of phenotypic mismatch across the range of their coevolutionary interaction. Geographic patterns of phenotypic exaggeration were similar in prey and predators, with most phenotypically elevated localities occurring along the central Oregon coast and central California. Contrary to expectations, however, these areas of elevated traits did not coincide with the most intense coevolutionary selection. Measures of functional trait mismatch revealed that over one-third of sampled localities were so mismatched that reciprocal selection could not occur given current trait distributions. Estimates of current locality-specific interaction selection gradients confirmed this interpretation. In every case of mismatch, predators were “ahead” of prey in the arms race; the converse escape of prey was never observed. The emergent pattern suggests a dynamic in which interacting species experience reciprocal selection that drives arms-race escalation of both prey and predator phenotypes at a subset of localities across the interaction. This coadaptation proceeds until the evolution of extreme phenotypes by predators, through genes of large effect, allows snakes to, at least temporarily, escape the arms race.
