《经济学家》读译参考（第13篇）：一路繁衍——你知道外来入侵物种吗？Go forth and multiply一往无前，生生不息WHAT makes for a successful invasion? Often, the answer is to have better weapons than the enemy. And, as it is with people, so it is with plants—at least, that is the conclusion of a p_______①published in ★Biology Letters[1] by Naomi Cappuccino, of Carleton University, and Thor Arnason, of the University of Ottawa, both in Canada.怎样才能成功入侵？答案常常是：拥有比敌人更好的武器。
人是这样，植物也是如此——至少，《生物书简》上发表的一篇论文是这么认为的，作者是来自加拿大加里敦大学的纳奥米•卡普奇诺和渥太华大学的索尔•阿纳森。
The phenomenon of alien species ★popping up[2] in unexpected parts of the world has grown over the past few d________② as people and goods become more mobile and （1）►plant seeds and animal larvae have ★hitched[3] along for the ride◄. Most such aliens blend into the ecosystem in which they arrive without too much fuss. (Indeed, many probably fail to establish themselves at all—but those failures, of course, are never noticed.) Occasionally, though, something ★goes bananas[4] and starts trying to take the place over, and an invasive species is born. Dr Cappuccino and Dr Arnason asked themselves w_______③.过去的几十年，随着人和货物的流动日益频繁，植物种子和动物幼体也乘机“搭便车”四处播散，世界各地无意间出现了越来越多的外来物种。
这些外来物种大多数都轻而易举地融入了所到之处的生态系统。
（事实上，许多物种可能还没有站稳脚跟——当然，人们从未注意到这一点。
）不过，偶尔也有某些物种疯狂繁殖，开始企图占领原有物种的生长空间，一种入侵物种就这样形成了。
卡普奇诺和阿纳森对此感到百思不得其解。
One hypothesis is that aliens leave their predators b________④. Since the predators in their new homelands are not adapted to exploit them, they are able to reproduce unchecked. That is a nice idea, but it does not explain why only certain aliens become invasive. Dr Cappuccino and Dr Arnason suspected this might be because native predators are [b]（2）►sometimes “pre-adapted” to the aliens' defences◄, but in other cases they are not.有人推想，外来物种摆脱了原先的掠食者，而在新的“家园”，现有的掠食者又没有发现它们也合口味，因此这些物种得以肆无忌惮地繁衍。
这种观点好是好，不过没有解释为什么只有特定的外来物种才具有入侵性。
卡普奇诺和阿纳森猜测，这可能是因为土生土长的掠食者对外来物种所具有的防御机制有时产生“预适应”，有时又不产生。
To test this, they had first to establish a reliable list of invaders. That is not as easy as it sounds. As they obs erve, “although there are many lists of invasive species published by governmental agencies, inclusion of a given species in the lists （3）►may not be entirely free of political motivation◄”. Instead, they polled established researchers in the field of alien species, asking each to list ten invasive species and, for c_________⑤, ten aliens that just ★rubbed along quietly with[5] their neighbours. The result was a list of 21 species widely agreed to be invasive and, for comparison, 18 non-invasive aliens.为了证实这一猜测，他们必须首先列出一些已经确认的入侵物种。
这可不是件轻松的事。
正如他们所说，“虽然政府部门公布了许多入侵物种名单，但是把指定物种归入此名单也许多少有些出于政治上的考虑。
”为此，他们调查了外来物种领域一些有名望的研究人员，请每人举出10种入侵物种，以及10种与本地物种能和睦共生的外来物种用于对照。
最后得到的名单中包括21种被广泛认可的入侵物种和18种用于对照的非入侵性外来物种。
H________⑥established these lists, they went to the library to find out what was known about the plants' chemistry. Their aim was to find the most prominent chemical weapon in each plant, whether that weapon was directed against insects that might want to eat the plant, bacteria and fungi that might want to i_______⑦it, or other plants that might compete for space, water, nutrients and light. Botanists know a lot about which sorts of compounds have what roles, so classifying constituent chemicals in this way was not too hard.名单确定之后，他们就到图书馆查询这些植物的化学性质，旨在找出每种植物所拥有的作用最为突出的“化学武器”。
这种“化学武器”的攻击对象包括可能吃掉该植物的昆虫，使其感染的细菌和真菌以及与其竞争生长空间、水、养料和阳光的其它植物。
植物学家对哪些化合物有哪些作用都了如指掌，因此这样对化学物质进行分类并不太难。
The researchers then compared the chemical arsenals of their aliens with those of native North American plants, （4）►to see if superior (or, at least, unusual) weaponry was the explanation for the invaders' success.◄ Their hypothesis was that highly invasive species would have chemical weapons not found in native plants, and w________⑧ pests, parasites and other plants would therefore not have evolved any resistance to. The more benign aliens, by contrast, were predicted to have arsenals also found in at least some native species.然后，为了弄清外来物种的成功入侵是否得益于“超级武器“（或者至少是超常武器），这两位研究人员将已知外来物种的“化学武器库”同北美土生土长的植物“化学武器库”进行了比较。
他们推断，具有高度入侵性的物种拥有土产植物所缺少的“化学武器”，对这种化学武器，害虫、寄生虫及其它植物都不能产生任何抵抗力。
相比之下，入侵性较弱的外来物种所具有的“武器库”可能至少同样存在于某些土产物种。
And so it proved. More than 40% of the invasive species had a chemical unknown to native plants; just over 10% of the non-invasive aliens had such a chemical. M_________⑨, when they looked at past studies on alien plants that had examined how much such plants suffer from the★depredations[6] of herbivorous insects, they found that the extent of the damage reported was significantly correlated with the number of native species with which that alien shared its principal chemical weapon.猜测因而得到了证实。