从深处
Volcanic islands, as newly formed lands emerging from the ocean depths, are often sources of evolutionary novelties. Effectively blank canvases when they first appear, plants and animals that find their way to these new islands often evolve into unique forms.
玛斯加罗群岛 - 毛里求斯，雷尼翁和罗德里格斯 - 是此类地方的绝佳例子。此后，在东非海岸出现了（与马达加斯加和塞舌尔等附近的其他岛屿相比），此后，成千上万种独特的动植物种类在这些岛屿上发展了。
尽管这些物种中的许多物种在最近几个世纪（包括纪念物）中与人类定居者的接触尚未幸免，但乳脂状的仍然是世界上一些最独特的野生动植物的家园。
所有这些物种都从祖先演变而来，这些祖先很久以前就找到了前往这些偏远岛屿的路：一只暴风雨吹走了一只鸟，一只种子漂浮在海洋上等。这些事件不太可能，但在整个过程中数百万年的发生足以使这些岛屿被不同的创始人物种殖民多次。
但是，自然而然地，我们希望这些殖民者来自最接近玛斯卡雷群岛的土地。对于岛上的绝大多数物种来说，确实是这种情况，在马达加斯加或东非发现了最亲密的祖先。
这使得关于玛斯龙棍昆虫起源的新研究结果，本周出版inBMC Evolutionary Biology，更令人惊讶。他们认为，这些物种的祖先不是来自附近的非洲，而是来自大洋洲的岛屿 - 超过5000公里。
Stick insect ancestries
研究人员，由托马斯·巴克利在新西兰的奥克兰大学，从38种昆虫物种（包括毛里求斯和Réunion的几乎所有已知物种）中提取和测序DNA，并将这些数据与来自其他83种物种的已知序列相结合。然后创建了一个系统发育树，以估计这些物种之间的进化关系。
The assembled data represents the most comprehensive study of stick insect evolution yet; it is also the first study to include species sampled from Indian Ocean islands. The overall pattern of stick insect evolution matches that seen in previous studies. However the results on the evolutionary origins of the Mascarene stick insects were rather more surprising.
玛斯卡烯棒昆虫在外观和行为上都表现出显着的多样性。基于这种多样性，它们可以大致订购为五个截然不同的群体。值得注意的是，这些不同的群体非常类似于马达加斯加和非洲发现的棍子群体。可以理解的那样，分类学家长期以来一直以为五组玛斯加罗棍昆虫彼此无关，并起源于这些岛屿的五个不同的殖民地。
Yet the researchers results strongly support a single common ancestor for all Mascarene stick insects; that is, the incredibly diverse assemblage of species found on the islands have all evolved from one original colonizing species. The apparent similarities with mainland stick insects do not represent shared evolutionary histories but are instead remarkable examples of收敛进化.
棍子航行
While this is an unexpected finding, even more extraordinary is what the results tell us about the origins of this original colonizing species. The evolutionary tree strongly places the Mascarene stick insects as most closely related to stick insects from Australasia. Instead of making the relatively short trip from nearby Madagascar, the original founding species reached the Mascarenes by traveling over 5000km across the Indian Ocean.
How could a stick insect (which generally are poor fliers) travel such a long distance? Most likely, stick insect eggs, which are hard-shelled and seed like, floated along the ocean currents, whether directly in the water or attached to twigs or other plant material.Recent research已经表明，现代棍子昆虫卵在漂浮在海水上时可以生存几个月。
尽管棍子昆虫卵的几率成功地幸存了这一旅程（然后在岛上成功地繁荣起来）肯定是遥远的，但只有一次，一个物种才能在一个新岛上建立自己。确实，这么长的航行在进化史上已经发生了多次。最近的其他研究表明，塞舌尔中的昆虫也起源于大洋洲，而geckos and skinks在睫毛菌中发现的似乎也经历了同样的旅程。
Voyaging to an island that doesn’t yet exist
As if this story were not amazing enough, the researchers also estimate that stick insects arrived in the Mascarene islands around 20 million years ago. Geological records show that Mauritius emerged from the sea only 8-10 million years ago, while Réunion and Rodrigues are much younger still. The Mascarene stick insects then, are older than the land they live on.
How can this be? The authors believe that the founding stick insects must originally have arrived on nearby islands that were above sea level at this time but have since sunk back beneath the waves. Indeed the geological record finds plenty of evidence for such older islands having existed as recently as the last ice age.
创始的棍棒昆虫在这些现在消失的岛屿上被冲走了，很可能在这里演变成当今发现的大多数形式中的大多数。这些岛屿似乎比现代睫毛菌大得多，这将为物种形成提供更好的条件。当这些岛屿逐渐沉没在海浪和毛里求斯和后来的Réunius和Rodrigues下方时，棍子昆虫移到了我们今天发现的新土地上。
The story of the Mascarene stick insects is an extraordinary one. From a few eggs that sailed thousands of miles across the ocean and washed up on a distant island that no longer exists, have evolved the numerous forms of most dazzling diversity we admire today.
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