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Stickleback快速平行進化:所謂宏進化問題的破產
JDT在大量證據面前,不得不承認一些可觀察的進化的事實,比如細菌抗藥性,病毒的快速
變異.但他們繼續試圖否認進化這一事實,創造了所謂微進化和宏進化這一區別.這樣就
能接著圓"創造各從其類"的神話.
所謂微進化和宏進化這一區別根本就是人為的主觀界定.他們其實
是一回事.
2005 Science 一篇關於Stickleback(見圖)快速平行進化的paper,用事實證明單一基因
的變異,足以造成宏觀的生物體結構差異.這一成果被評為該年十大科學突破之一.
Science's Breakthrough Of The Year: Watching Evolution In Action
ScienceDaily (Dec. 25, 2005) http://www.sciencedaily.com/releases/2005/12/051224100718.htm...."studies showed how small changes in DNA can trigger dramatic evolutionary events. Researchers found that a single genetic change can be all it takes to turn one species into many, as in the case of the Alaskan stickleback fish that lost its armor and evolved from an ocean-loving species to a variety of landlocked lake dwellers."
圖中魚叫stickleback. 海里的生活在阿拉斯加,體表有完整的骨質凱甲,而北半球各大
陸淡水湖中的多種stickleback不約而同都喪失了這骨質凱甲.研究表明在一萬多年前冰
川退縮時,海stickleback被留在眾多北半球的冰川退縮后形成的與海隔絕的淡水湖裡,這些互不相鄰的幾個大陸上的
淡水湖裡的stickleback都不約而同進化而失去了完整的骨質凱甲,適應的原因可能有:1,淡水Ca
水平低, 2. Predator 少,耗費能量資源長完整的骨質凱甲反而成了不利因素;3.覓食條
件改變,沒有骨質凱甲更靈活.
冰川退縮這一事件,使眾多淡水湖的每一個都成了獨立的平行的進化實驗,而實驗結果是:進化形成
的不同種淡水stickleback有一共同點,都喪失了完整的骨質凱甲.
線粒體遺傳分析表明這些不同湖裡的stickleback並不是來源於一個喪失了骨質凱甲的
共同祖先(relocation is not possible due to geological separation),而是分別各
自從海stickleback這一共同祖先獨立進化來的.
Stanford這一實驗室的遺傳學分析表明,這一宏觀上的差異,起源是同一個基因Eda.這一
微小的單一基因的變異造成了整體外觀的顯著不同. 可以envision,在這一差異基礎上,
累積其他差異,形成了如今眾多的各種淡水種stickleback.
另:人類依然保有Eda基因,主要和皮膚,汗腺,毛髮有關.
這是非常有力的證據說明所謂微進化和宏進化是人為的劃分而沒有事實根據.
這裡是原文摘要供感興趣的同學閱讀.
Science 25 March 2005:
Vol. 307. no. 5717, pp. 1928 - 1933
DOI: 10.1126/science.1107239 Prev | Table of Contents | Next
Research Articles
Widespread Parallel Evolution in Sticklebacks by Repeated Fixation of
Ectodysplasin Alleles
Pamela F. Colosimo,1 Kim E. Hosemann,1 Sarita Balabhadra,1 Guadalupe
Villarreal, Jr.,1 Mark Dickson,3 Jane Grimwood,3 Jeremy Schmutz,3 Richard M.
Myers,3 Dolph Schluter,4 David M. Kingsley1,2
Major phenotypic changes evolve in parallel in nature by molecular
mechanisms that are largely unknown. Here, we use positional cloning methods
to identify the major chromosome locus controlling armor plate patterning
in wild threespine sticklebacks. Mapping, sequencing, and transgenic studies
show that the Ectodysplasin (EDA) signaling pathway plays a key role in
evolutionary change in natural populations and that parallel evolution of
stickleback low-plated phenotypes at most freshwater locations around the
world has occurred by repeated selection of Eda alleles derived from an
ancestral low-plated haplotype that first appeared more than two million
years ago. Members of this clade of low-plated alleles are present at low
frequencies in marine fish, which suggests that standing genetic variation
can provide a molecular basis for rapid, parallel evolution of dramatic
phenotypic change in nature.
1 Department of Developmental Biology, Stanford University School of
Medicine, Stanford, CA 94305–5329, USA.
2 Howard Hughes Medical Institute, Stanford University School of Medicine,
Stanford, CA 94305–5329, USA.
3 Department of Genetics and Stanford Human Genome Center, Stanford
University, Stanford, CA 94305–5120, USA.
4 Zoology Department and Biodiversity Research Centre, University of British
Columbia, Vancouver, British Columbia, Canada, V6T 1Z4.
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這裡科普版的介紹,介紹這一重大成果的意義.
Same Mutation Aided Evolution In Many Fish Species, Stanford Study Finds
ScienceDaily (Mar. 29, 2005) — STANFORD, Calif. – After decades of
laboratory work studying how animals evolve, researchers sometimes need to
put on the hip waders, pull out the fishing net and go learn how their
theory compares to the real world. According to a Stanford University School
of Medicine study published in the March 25 issue of Science, Mother Nature
is more predictable than lab experiments suggest.
In a diverse group of fish called the stickleback, nature took advantage of
the same genetic trick time and again to allow freshwater species to shed
their burdensome body armor and transform into a lighter, spryer fish. This
is among the first times scientists have shown that the same genetic change
is responsible for an evolutionary adaptation in disparate populations.
「Almost every time the stickleback evolves in fresh water it loses the
armor,」 said David Kingsley, PhD, professor of developmental biology and
lead author of the study. 「Although the trait evolved many times all over
the world, nature uses the same gene each time.」
Sticklebacks evolved from a relatively uniform marine population into today
』s broad spectrum of shapes and sizes when the last Ice Age ended roughly
10,000 years ago. Because ocean fish quickly evolved into such distinct
populations when they colonized new freshwater lakes and streams, they are
an ideal model for understanding how animals adapt to their unique
environments.
The recent work carries a few surprises. Kingsley said that the gene in
question, called Eda, is an old friend to laboratory researchers who have
found that mutations in the same gene in mice cause altered hair patterns.
However, in mice similar alterations can also be created by defects in any
one of three different genes. 「Based on the mouse work you』d predict we
would find mutations in any of the three genes in sticklebacks,」 said
Kingsley, who is also a Howard Hughes Medical Institute investigator. 「That
』s not what we see.」
Instead, the group found the exact same genetic change in each of the 15
freshwater sticklebacks they studied, including one local species the group
collected from a stream near Fresno. Perhaps mutations in the two other
genes cause problems for the fish in addition to reducing the number of
armor plates, Kingsley said.
Most of these fish evolved independently from marine ancestors that are
covered head to hind fin in body armor. Although it』s not clear why losing
the armor is a benefit to freshwater fish, Kingsley noted that the unarmored
fish are lighter and faster than their more burdened marine cousins.
In an effort to learn more about how the armor trait evolves so quickly,
Kingsley and his colleagues sequenced that genetic region in a large number
of marine fish, all of which had a complete set of armor plates. A small
number of these fish had one copy of the Eda gene that contained the
mutation in question.
It』s likely that when a pocket of sticklebacks got isolated, at least a few
of those fish already carried the mutated copy of the Eda gene. When those
fish bred, some gave rise to offspring with two copies of the mutation and
no (or reduced) body armor. In a freshwater habitat those fish prospered and
populated the stream or lake with similarly armorless offspring.
Kingsley said this work is part of a larger study to understand how
evolution generates major morphological and physiological changes. 「We want
to learn how evolution works on a large scale,」 he said. In previous work,
his group found that several species of stickleback lacking hind fins all
shared an alteration in how a gene was turned on and off.
The striking similarity is that in both studies evolution turned to the same
genetic switch to work a visible change in the fish. However, in the fin
study the group wasn』t able to pinpoint the exact genetic alteration.
The group continues to wade out into nature, collecting additional
stickleback species from around the world that can reveal whether particular
genes are always reused when the animals adapt to new conditions, or if
evolution has other tricks up its sleeve to push organisms towards an
optimal form for their environment.
Other Stanford researchers who participated in the study include graduate
students Pamela Colosimo, PhD, first author on the study, and Kim Hosemann;
technician Sarita Balabhadra; undergraduate Guadalupe Villarreal Jr.;
technical managers at the Stanford Human Genome Center Mark Dickson, Jane
Grimwood and Jeremy Schmutz; and Richard Myers, PhD, professor of genetics. |
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