How Ecotypes Harbor the Genetic Memory of a Species’ Past
The green ecotype of Cristina’s timema, a species of stick insect, blends in with broad leaves.
Cristina's timema（一种竹节虫）的绿色生态型与宽阔的叶子融为一体。
Other ecotypes of the same species are colored to blend in with narrower leaves.
同一物种的其他生态型的颜色与较窄的叶子融为一体。
With genomics, scientists are answering century-old questions about how a single species can manifest such distinct traits.
通过基因组学，科学家们正在回答一个世纪以来的问题：单个物种如何表现出如此独特的特征。
When she was a graduate student in the 1970s, the evolutionary biologist Kerstin Johannesson regularly walked the shores of a Swedish archipelago, scanning the ground for pebbles that moved: marine snails.
20 世纪 70 年代，当进化生物学家 Kerstin Johannesson 还是一名研究生时，她经常在瑞典群岛的海岸上行走，扫描地面上移动的卵石：海洋蜗牛。
Her adviser, a taxonomist, had tasked her with describing the species present there by documenting their traits.
她的顾问是一位分类学家，他要求她通过记录物种的特征来描述那里的物种。
She noticed that snails with thicker shells stayed on the shore, while those with thinner shells seemed to prefer wave-battered rocks, and in between the two habitats were snails with intermediate shell thickness.
她注意到，壳较厚的蜗牛留在岸上，而壳较薄的蜗牛似乎更喜欢被海浪冲击的岩石，而在这两个栖息地之间的是壳厚度适中的蜗牛。
While they seemed like distinct species, Johannesson couldn’t help but wonder whether these snails might instead be different types of the same one.
虽然它们看起来像是不同的物种，但约翰内森忍不住想知道这些蜗牛是否可能是同一蜗牛的不同类型。
Around 50 years earlier, the botanist Göte Turesson had had a similar revelation in a similar setting.
大约 50 年前，植物学家 Göte Turesson 在类似的环境中也得到了类似的启示。
As he walked Sweden’s shores, he noticed that saltbush plants from different stretches of coastline had distinct traits — earlier or later flowering times, or shorter or longer stalks — and between habitats, those traits fell somewhere in the middle.
当他走在瑞典海岸时，他注意到来自不同海岸线的盐灌木植物具有不同的特征——开花时间早或晚，或者茎较短或较长——而在栖息地之间，这些特征处于中间位置。
He bred the plants in his home garden and found that these distinct traits had a genetic basis even though they arose from the same species.
他在自家花园中培育了这些植物，发现这些独特的特征具有遗传基础，即使它们来自同一物种。
In 1922, he published his results and coined the term “ecotype” to describe a subpopulation of a species adapted to a hyperlocal habitat.
1922 年，他发表了自己的研究结果，并创造了“生态型”一词来描述适应超本地栖息地的物种亚群。
Remarkably, some species can flip between two ecotypes after just a few generations — far shorter than the typically lengthy course of natural selection.
值得注意的是，一些物种只需几代就可以在两种生态型之间转换——比通常漫长的自然选择过程要短得多。
At that time, the definition of a species was even less clear than it is today .
那时候，物种的定义甚至比现在还不清楚。
Genes were still theoretical, and the structure of DNA wouldn’t be discovered for another 30 years.
基因仍然处于理论阶段，DNA 的结构还要 30 年才能被发现。
Turesson “struggled to be accepted,” said Johannesson , now the director of Tjärnö Marine Laboratory at the University of Gothenberg.
现任哥德堡大学 Tjärnö 海洋实验室主任的 Johannesson 表示，图雷森“很难被接受”。
How can a species contain multiple distinct phenotypes — or sets of traits — without separating into two species?
一个物种如何能够包含多种不同的表型（或一组性状）而不分成两个物种？
“He had quite a job to try to convince his colleagues that there were inherited differences and local adaptation within species,” she said.
“他的工作相当艰巨，要努力让同事相信物种内部存在遗传差异和局部适应，”她说。
It wasn’t until the early 2000s, when whole-genome sequencing became accessible to evolutionary biologists, that Turesson’s ideas about ecotypes could be tested.
直到 2000 年代初期，进化生物学家能够进行全基因组测序，图雷森关于生态型的想法才得以得到检验。
By comparing the DNA sequences of ecotypes across the tree of life — from marine snails to stickleback fish to stick insects and more — scientists can study adaptation and speciation, the process by which new species form, at a molecular level.
通过比较生命之树生态型的 DNA 序列——从海洋蜗牛到刺鱼再到竹节虫等——科学家可以在分子水平上研究适应和物种形成，即新物种形成的过程。
Since the 1970s, the evolutionary biologist Kerstin Johannesson has tried to understand how various forms of marine snail could possibly represent the same species.
自 20 世纪 70 年代以来，进化生物学家 Kerstin Johannesson 一直试图了解不同形式的海洋蜗牛如何可能代表同一物种。
“It’s by far the most exciting time to be a biologist, ever, in my opinion — maybe with the exception of going right back to Darwin,” said Sean Stankowski , an evolutionary geneticist at University College London.
“在我看来，这是迄今为止作为一名生物学家最激动人心的时刻——也许除了直接回到达尔文之外，”伦敦大学学院的进化遗传学家肖恩·斯坦科夫斯基说。
“Even when we understood that organisms were programmed by genetic code, we could really never access that.
“即使我们了解生物体是由遗传密码编程的，我们也永远无法访问它。
Now, we’re looking at every single [nucleotide molecule] — A, T, G, and C [adenine, thymine, guanine, and cytosine] — in the genome.”
现在，我们正在研究基因组中的每一个[核苷酸分子]——A、T、G和C[腺嘌呤、胸腺嘧啶、鸟嘌呤和胞嘧啶]。”
An analysis of genomic ecotypes by Johannesson, Stankowski, and other researchers explains how some species can maintain the DNA sequences for multiple adaptations, allowing evolutionary processes to effectively select among ecotypes as environmental conditions change — sometimes within only a few generations.
Johannesson、Stankowski 和其他研究人员对基因组生态型的分析解释了一些物种如何维持 DNA 序列以进行多种适应，从而使进化过程能够随着环境条件的变化而有效地选择生态型——有时只需几代之内。
The data also suggests that some canonically diverse groups of species, including Darwin’s finches, may not be separate species at all, but rather different ecotypes of the same species.
数据还表明，一些典型的不同物种群体，包括达尔文雀，可能根本不是单独的物种，而是同一物种的不同生态型。
Ecotypes represent a kind of “genetic memory,” Stankowski said, that reflects a species’ history of survival in different habitats.
斯坦科夫斯基说，生态型代表了一种“遗传记忆”，反映了一个物种在不同栖息地的生存历史。
“Genomics has just taught us everything that’s going on under the hood,” he said.
“基因组学告诉了我们幕后发生的一切，”他说。
Once scientists looked there, they found an engine for adaptation.
一旦科学家们观察到那里，他们就发现了适应的引擎。
In March 1964, the largest earthquake ever documented in North America uprooted the Gulf of Alaska.
1964 年 3 月，北美有记录以来最大的地震将阿拉斯加湾连根拔起。
Within four minutes, some of the gulf’s islands were lifted 38 feet in the air, rivers were closed off from the ocean, and freshwater lakes were created.
不到四分钟，海湾的一些岛屿就被提升到了 38 英尺高的高度，河流与海洋的联系被封闭，淡水湖也随之形成。
A decade later, scientists were surprised to find three-spined sticklebacks thriving there.
十年后，科学家们惊讶地发现三刺鱼在那里繁衍生息。
The fish species typically lives in the salty ocean.
该鱼通常生活在咸海中。
Biologists might have expected it to die out in a freshwater lake.
生物学家可能预计它会在淡水湖中灭绝。
Instead, something more interesting happened.
相反，更有趣的事情发生了。
The marine sticklebacks, which are armed against ocean predators with bony plates, started to look and behave like their freshwater cousins, which have fewer plates.
海洋刺鱼用骨板来对抗海洋掠食者，它们的外观和行为开始像它们的淡水表亲一样，后者的骨板较少。
This change unfolded within decades, too fast for a new species to have formed.
这种变化在几十年内就发生了，速度太快，不足以形成新物种。
Marine sticklebacks (top) are armored with bony plates (stained red), which provide protection from ocean predators.
海洋刺鱼（上）身披骨板（染成红色），可以抵御海洋掠食者。
Freshwater sticklebacks (bottom) have fewer plates and swim faster than the marine ecotype.
淡水刺鱼（下）的板块较少，而且比海洋生态型游得更快。
What could have driven these rapid phenotypic changes?
是什么驱动了这些快速的表型变化？
A 50-year study of genomic data, published in 2015, revealed that, tucked into genomes across the population, marine sticklebacks contained the genes necessary to survive in freshwater environments.
2015 年发表的一项历时 50 年的基因组数据研究表明，海洋刺鱼的基因组中含有在淡水环境中生存所需的基因。
These alternate genes occur sparingly across roughly 100 regions of the genome, said Catherine Peichel , an evolutionary geneticist at the University of Bern who studies the fish species.
伯尔尼大学研究鱼类的进化遗传学家 Catherine Peichel 表示，这些替代基因很少出现在基因组的大约 100 个区域中。
The presence of this kind of genetic diversity — having multiple forms of the same gene that harbor different traits — is known as standing variation.
这种遗传多样性的存在——具有不同特征的同一基因的多种形式——被称为常备变异。
Even in low numbers, those alternate genes have a chance to be expressed, as if natural selection could reach into the past and redeploy those genes when needed.
即使数量很少，这些替代基因也有机会表达，就好像自然选择可以追溯到过去并在需要时重新部署这些基因一样。
Research from a different lab has shown that transplanted marine sticklebacks can switch to the freshwater ecotype in as few as 20 to 30 years.
另一个实验室的研究表明，移植的海洋刺鱼可以在短短 20 到 30 年内转变为淡水生态型。
The emergence of and selection for a novel trait, on the other hand, would likely take far longer than that — if the fish even survived the initial shock of navigating a totally different habitat.
另一方面，如果鱼能够在完全不同的栖息地的最初冲击中幸存下来，那么新特征的出现和选择可能需要比这更长的时间。
“It’s almost like populations have a genetic memory of their time spent in different environments,” Stankowski said.
斯坦科夫斯基说：“这几乎就像人们对在不同环境中度过的时间有遗传记忆一样。”
Back in Sweden, Johannesson’s marine snails seemed to harbor this genetic memory, too.
回到瑞典，约翰内森的海洋蜗牛似乎也拥有这种遗传记忆。
In 1988, a few years after she completed her doctorate, a rare algal bloom blanketed Scandinavian coastlines with a lime-green slime that killed almost all marine life.
1988 年，也就是她完成博士学位几年后，斯堪的纳维亚海岸线上出现了一种罕见的藻华，石灰绿色的粘液覆盖了几乎所有的海洋生物。
“All my snails, they were gone,” she recalled.
“我所有的蜗牛都消失了，”她回忆道。
But she turned the tragedy into an opportunity.
但她把悲剧变成了机会。
Many isolated rock islands were left vacant, so she ran a natural experiment to see if she could trigger her snails to switch ecotypes.
许多孤立的岩石岛屿都空置了，所以她进行了一项自然实验，看看是否可以触发她的蜗牛改变生态型。
The marine snail Littorina saxatilis has been accidentally described as a new species or subspecies more than 100 times.
海洋蜗牛 Littorina saxatilis 已被意外地描述为新物种或亚种超过 100 次。
In fact, the species includes two ecotypes (side-by-side, top) — one larger with thick shells, the other smaller and thinner — adapted to different habitats.
事实上，该物种包括两种生态型（并排、顶部）——一种较大，壳厚，另一种较小、较薄——适应不同的栖息地。
The marine snail Littorina saxatilis has been accidentally described as a new species or subspecies more than 100 times.
海洋蜗牛 Littorina saxatilis 已被意外地描述为新物种或亚种超过 100 次。
In fact, the species includes two ecotypes (side-by-side, at left) — one larger with thick shells, the other smaller and thinner — adapted to different habitats.
事实上，该物种包括两种生态型（并排，左）——一种较大，壳较厚，另一种较小且较薄——适应不同的栖息地。
David Carmelet; Roland Carlsson
大卫·卡梅莱特；罗兰·卡尔森
Large, thick-shelled snails had armor to protect them from predatory crabs onshore; smaller snails could more easily cling to wave-battered rocks.
厚壳的大蜗牛有盔甲，可以保护它们免受岸上掠食性螃蟹的侵害。较小的蜗牛可以更容易地附着在被海浪击打的岩石上。
With the help of her then-3-year-old daughter, Johannesson collected hundreds of large snails and placed them on empty rocks exposed to the sea.
在当时 3 岁女儿的帮助下，约翰内森收集了数百只大蜗牛，并将它们放在暴露在大海中的空岩石上。
As the years turned into decades, and as generations of snails came and went, the entire population became smaller, with thinner shells.
岁月流逝，几十年过去了，一代又一代的蜗牛来了又去，整个种群变得越来越小，壳也越来越薄。
In less than 30 years, the wave-battered ecotype had been selected for across the population.
在不到 30 年的时间里，受海浪侵袭的生态类型已被选为整个人群的选择。
A few years later, she would uncover the genomic features that made the snails’ rapid adaptation possible.
几年后，她发现了使蜗牛快速适应的基因组特征。
A given ecotype might require the expression of hundreds of genes.
给定的生态型可能需要数百个基因的表达。
So how can selection act on all of them at once?
那么选择如何同时作用于所有这些呢？
Genomic studies have found explanations in chromosomal architecture.
基因组研究已经找到了染色体结构的解释。
During egg and sperm formation, genes can be shuffled between chromosomes (highly compact packages of DNA) in a process known as recombination.
在卵子和精子形成过程中，基因可以在染色体（高度紧凑的 DNA 包）之间进行重组，这一过程称为重组。
Some portions of DNA can be deleted or inserted.
DNA 的某些部分可以被删除或插入。
Chromosomes can break into two, or fuse into one.
染色体可以分裂成两条，也可以融合成一条。
And entire segments of DNA can be flipped, in what is called an inversion.
DNA 的整个片段可以被翻转，这就是所谓的倒置。
An inversion happens when a portion of DNA from the chromosome breaks off, rotates 180 degrees, and plugs back into the chromosome in the reverse orientation.
当染色体上的一部分 DNA 断裂、旋转 180 度并以相反方向插回染色体时，就会发生倒位。
After inversion, a block of genes sits in one orientation on one chromosome, and in the opposite orientation on the other.
倒转后，一组基因在一条染色体上以一个方向排列，而在另一条染色体上则以相反的方向排列。
This effectively prevents recombination from happening again in that region, and locks that group of genes together in a block.
这有效地防止了该区域再次发生重组，并将该组基因锁定在一个块中。
If those genes are somehow related, this can create a supergene , or multiple genes that act as a single unit.
如果这些基因以某种方式相关，则可以创建一个超基因，或作为一个单元的多个基因。
The snail traits for thick shells and evasive behavior to hide from crabs, for instance, become linked so that they will be inherited together in subsequent generations.
例如，厚壳的蜗牛特征和躲避螃蟹的逃避行为相互关联，因此它们将在后代中一起遗传。
“It’s like if you had a deck of cards,” said Patrik Nosil , an evolutionary geneticist at the French National Center for Scientific Research who studies speciation and ecotypes of stick insects.
“这就像你有一副牌一样，”法国国家科学研究中心的进化遗传学家帕特里克·诺西尔（Patrik Nosil）说，他研究竹节虫的物种形成和生态型。
“With normal genetics, you shuffle that deck completely — all 52 cards.
“凭借正常的基因，你可以将这副牌完全洗牌——全部 52 张牌。
Whereas with these chromosomal inversions, you have a part of the deck that refuses to shuffle, so you can never change the order of the cards in there.
然而，通过这些染色体倒置，你的牌组中有一部分拒绝洗牌，因此你永远无法改变其中牌的顺序。
That’s the part that controls the traits that make the ecotypes different.”
这是控制使生态型不同的特征的部分。”
This is what Peichel suspects happened in the sticklebacks.
这就是佩切尔怀疑棘鱼身上发生的事情。
Even though they still mate across ecotypes (marine sticklebacks return to freshwater inlets to breed), past inversions ensure that the freshwater genes stay together and that the marine genes do too, she said.
她说，尽管它们仍然跨生态型交配（海洋刺鱼返回淡水入口繁殖），但过去的倒转确保了淡水基因保持在一起，海洋基因也保持在一起。
This differentiates the two ecotypes while maintaining species-wide gene flow.
这区分了两种生态型，同时维持了物种范围的基因流。
It’s by far the most exciting time to be a biologist, ever.
这是迄今为止作为一名生物学家最激动人心的时刻。
Sean Stantowski, University College London
肖恩·斯坦托夫斯基，伦敦大学学院
Peichel’s lab is getting closer to confirming this hypothesis.
佩切尔的实验室越来越接近证实这一假设。
Using the gene-editing technology CRISPR, her lab can flip an inversion back to its original orientation.
使用基因编辑技术 CRISPR，她的实验室可以将反转翻转回其原始方向。
As these sticklebacks reproduce, the genes in this region will be able to shuffle again, perhaps disrupting the suite of traits that form the ecotypes.
随着这些刺鱼的繁殖，该区域的基因将能够再次洗牌，或许会破坏形成生态型的一系列性状。
“This would be some of the first proof of this idea that inversions actually bring together, and hold together, adaptive [genes] that distinguish ecotypes,” Peichel said.
“这将是这个想法的第一个证据，即倒位实际上将区分生态型的适应性[基因]聚集在一起，并结合在一起，”佩切尔说。
Inversions aren’t always beneficial.
倒置并不总是有益的。
They come with risks, including reproductive failure.
它们伴随着风险，包括生殖障碍。
For example, thousands of inversions have been identified in the human genome, and some can cause pregnancies to fail.
例如，人类基因组中已发现数以千计的倒位，其中一些可能导致怀孕失败。
But when they successfully hold groups of traits together, the rewards can be high.
但当他们成功地将一组特征结合在一起时，回报就会很高。
Indeed, Johannesson and Stankowski’s review surfaced inversions associated with ecotypes across the tree of life, including in plants, birds, fish, mammals, marine invertebrates, and insects.
事实上，约翰内森和斯坦科夫斯基的评论揭示了与生命之树生态型相关的倒置，包括植物、鸟类、鱼类、哺乳动物、海洋无脊椎动物和昆虫。
“No one predicted that [inversions] would be as abundant as they are” in ecotypes, Stankowski said.
斯坦科夫斯基说，“没有人预测到生态型中的[倒转]会如此丰富”。
“In evolutionary genetics, it’s probably one of the biggest realizations of the last two decades.”
“在进化遗传学领域，这可能是过去二十年最大的成就之一。”
And some ecotypes contain many chromosomal inversions.
有些生态型含有许多染色体倒位。
By the mid-2010s, Johannesson and her colleagues had identified nearly 20 different ecotype-related inversions in the marine snail genome.
到 2010 年代中期，Johannesson 和她的同事在海洋蜗牛基因组中发现了近 20 种不同的与生态型相关的倒位。
Interestingly, these same groups of traits are found across populations — in Spain and the United Kingdom as well as Sweden — even though these populations are isolated and don’t interbreed.
有趣的是，这些相同的特征在西班牙、英国以及瑞典的人群中都存在，尽管这些人群是孤立的并且不杂交。
Further analysis showed that some of these inversions are millions of years old, likely having occurred in a common ancestor.
进一步的分析表明，其中一些倒转已有数百万年的历史，很可能发生在一个共同的祖先身上。
Cristina’s timema has several ecotypes, fit for different leaf types.
克里斯蒂娜的timema有多种生态型，适合不同的叶子类型。
The stick insects sporting a stripe (top) blend in with narrow leaves, while green ones (bottom) match broad leaves.
带有条纹的竹节虫（上）与窄叶融为一体，而绿色的竹节虫（下）则与宽叶相匹配。
Cristina’s timema has several ecotypes, fit for different leaf types.
克里斯蒂娜的timema有多种生态型，适合不同的叶子类型。
The stick insects sporting a stripe (left) blend in with narrow leaves, while green ones (right) match broad leaves.
带有条纹的竹节虫（左）与窄叶融为一体，而绿色的竹节虫（右）则与宽叶相匹配。
“These inversions, which are big chunks of the DNA, were not really obvious until we had a reference genome and a genetic map,” Johannesson said.
“这些倒位是 DNA 的大块，直到我们有了参考基因组和遗传图谱后才真正明显，”Johannesson 说。
“When this [ result ] came, it was like we got to the end of the story.”
“当这个[结果]到来时，我们就好像故事到了结局。”
To be clear, not all chromosomal inversions form ecotypes, and ecotypes aren’t necessarily formed by inversions.
需要明确的是，并非所有染色体倒位都会形成生态型，生态型也不一定是由倒位形成的。
Indeed, another chromosomal recombination process that preserves blocks of genes can be found in California’s dry, shrubby chaparral mountains, where the walking stick insect Cristina’s timema ( Timema cristinae ) is made for camouflage.
事实上，另一种保存基因块的染色体重组过程可以在加利福尼亚州干燥、灌木丛生的丛林山脉中发现，那里的手杖昆虫克里斯蒂娜·克里斯蒂娜 (Timema cristinae) 就是为了伪装而生的。
One of its ecotypes has a stripe down its back and feeds on plants with narrow leaves; the other is bright green and stripeless, and feeds on broad leaves.
其中一种生态型的背部有一条条纹，以叶子狭窄的植物为食。另一种是亮绿色、无条纹，以宽叶为食。
Each ecotype blends in with its preferred food, which helps it avoid predators, Nosil said.
诺西尔说，每种生态类型都与它喜欢的食物融为一体，这有助于它躲避捕食者。
In these stick insects, as in the sticklebacks, a chromosomal inversion keeps each ecotype’s group of traits together on the genome.
在这些竹节虫中，就像在刺鱼中一样，染色体倒位使每个生态型的一组性状在基因组上保持在一起。
But Nosil’s research has found that the chromosomal changes don’t stop there.
但诺西尔的研究发现，染色体的变化并不止于此。
Translocation is another structural change to chromosomal DNA that can happen, by chance, during recombination.
易位是染色体 DNA 的另一种结构变化，可能在重组过程中偶然发生。
Genes from one end of a chromosome are relocated to the other end — an event that can get “really messy,” Nosil said.
诺西尔说，染色体一端的基因被重新定位到另一端——这一事件可能会变得“非常混乱”。
Some parts of the genome can disappear entirely, while other genes can be inserted into a new place.
基因组的某些部分可以完全消失，而其他基因可以插入到新的位置。
There’s another explanation for why structural rearrangements may form ecotypes.
对于为什么结构重排可能形成生态型还有另一种解释。
Chromosome breaks are rarely tidy, and sometimes they can lead to beneficial new traits.
染色体断裂很少是整齐的，有时它们会导致有益的新性状。
“Then that trait is favored by natural selection,” Nosil said.
“那么这个特征就会受到自然选择的青睐，”诺西尔说。
This idea that structural changes can create new functional mutations and not just prevent recombination is almost always overlooked, he said.
他说，结构变化不仅可以防止重组，还可以产生新的功能突变，这种想法几乎总是被忽视。
But his research into stick insects suggests that it can support the evolution of new ecotypes.
但他对竹节虫的研究表明，它可以支持新生态型的进化。
“Over the next years, that’ll become a big point of research,” he said, “to try to understand the relative importance of those two aspects of genomic rearranging.”
“在接下来的几年里，这将成为研究的一个重点，”他说，“试图了解基因组重排的这两个方面的相对重要性。”
Over the years, evolutionary biologists have debated whether ecotypes are a first step in the evolution of new species.
多年来，进化生物学家一直在争论生态型是否是新物种进化的第一步。
Are thick- and thin-shelled snails, marine and freshwater sticklebacks, or striped and solid stick insects examples of species on their way to splitting into two?
厚壳和薄壳蜗牛、海洋和淡水刺鱼、条纹和实心竹节虫是正在分裂成两个物种的例子吗？
“There’s been growing appreciation now that ecotypes might be a step in the direction of forming new species, but they might never actually get there,” Nosil said.
诺西尔说：“现在人们越来越认识到，生态型可能是朝着形成新物种的方向迈出的一步，但它们可能永远不会真正实现这一目标。”
The evolutionary geneticist Patrik Nosil collects stick insects.
进化遗传学家帕特里克·诺西尔收集竹节虫。
His research shows how chromosomes can rearrange to switch between ecotypes.
他的研究表明染色体如何重新排列以在生态型之间切换。
Speciation isn’t as clean-cut as the branches of a phylogenetic tree would have us believe.
物种形成并不像系统发育树的分支让我们相信的那样清晰。
Evolutionary biologists increasingly view it as smoothly scrolling across a continuum, rather than a process with discrete steps.
进化生物学家越来越认为它是在一个连续体中平稳滚动的过程，而不是一个具有离散步骤的过程。
There is a gray area between species, and that’s where ecotypes sit.
物种之间存在灰色地带，这就是生态型所在的地方。
The distinct marine and freshwater traits in sticklebacks, for example, suggest that they should diverge into two different species.
例如，刺鱼独特的海洋和淡水特征表明它们应该分化成两个不同的物种。
Yet even after millions of years, they haven’t.
然而，即使过了数百万年，他们仍然没有。
Instead, when environmental conditions change from salt water to fresh water, evolution seems to select for one ecotype or the other without discarding the alternate set of genes.
相反，当环境条件从咸水变为淡水时，进化似乎会选择一种生态型或另一种，而不会丢弃另一组基因。
Then again, the species concept has been controversial since the days of Darwin.
然而，自达尔文时代以来，物种概念一直存在争议。
What distinguishes one species from another, or a species from a subspecies, or an ecotype from simple variation, isn’t concrete.
一个物种与另一个物种、一个物种与一个亚种、一个生态型与简单变异的区别并不具体。
Genomics has both clarified and complicated the question.
基因组学既澄清了这个问题，又使这个问题复杂化了。
“The problem with defining ecotypes and the issue of defining species — they’re actually quite analogous,” Stankowski said.
“定义生态型的问题和定义物种的问题——它们实际上非常相似，”斯坦科夫斯基说。
“It really does boil down to cultural differences” in scientific perspectives, he added, such as how biologists are trained, what questions they ask, and whether they’re inclined to lump species together or split them up.
他补充说，从科学角度来看，“这确实归结为文化差异”，例如生物学家如何接受培训、他们提出什么问题，以及他们是否倾向于将物种归为一类还是将它们分开。
For instance, many taxonomists consider Darwin’s finches in the Galápagos to be distinct species.
例如，许多分类学家认为加拉帕戈斯群岛的达尔文雀是不同的物种。
However, they can change their beak shape to match the available seeds within generations, and they can all mate with one another.
然而，它们可以改变喙的形状以匹配几代内可用的种子，并且它们都可以相互交配。
By Stankowski and Johannesson’s criteria, Darwin’s finches “would all be ecotypes of a single species,” he said.
他说，按照斯坦科夫斯基和约翰内森的标准，达尔文雀“都将是单一物种的生态型”。
The same goes for cichlid fish in east Africa’s Lake Victoria, another famous example of rapid evolutionary radiation.
东非维多利亚湖的慈鲷也是如此，这是快速进化辐射的另一个著名例子。
But that doesn’t mean we need to rethink On the Origin of Species .
但这并不意味着我们需要重新思考《物种起源》。
“Darwin would be blown away at the progress that we’ve made,” Stankowski said.
“达尔文会对我们所取得的进展感到震惊，”斯坦科夫斯基说。
“The ecotype concept really does match quite closely with his view on species.”
“生态型概念确实与他对物种的看法非常吻合。”
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