加州一種野花揭示了一種新近記錄的進化過程（1/2）

Recently CNN.com reported the following:

A wildflower in California reveals a newly documented evolutionary process (1/2)

CNN  -  By Jacopo Prisco

UPDATED MAR 12, 2026

During California’s worst dry spell in the past 1,200 years, some populations of wildflowers defied the odds to survive the ordeal. Researchers say they now believe these flowers relied on a type of rapid genetic evolution — the first time such a phenomenon has been documented in the wild.

The dry spell happened between 2012 and 2015, and killed more than 100 million trees. It was a particularly brutal period during an ongoing megadrought that began in 2000 and which has been made worse by climate change. Even though the drought killed plants that are normally drought-resistant, the scarlet monkeyflower, a bright red wildflower that thrives in wet areas, and along creek beds and springs, showed remarkable resilience.

A team of researchers spent eight years studying 55 populations of the wildflower, whose scientific name is Mimulus cardinalis, by keeping track of its numbers in the wild and sequencing the flowers’ genomes to reveal genetic shifts.

“We were able to show that these populations across the range in California were declining due to this extreme drought, and we found evidence of a rapid evolution across the genome,” said Daniel Anstett, an assistant professor at the School of Integrative Plant Science of Cornell University and first author of a study on the findings, which published Thursday in the journal Science. “And then we were able to relate a metric of this evolution to the ability of these populations to recover and to not go extinct.”

While the entire species was not at risk of extinction, individual flower populations likely were, suffering declines of up to 90% compared to peak population sizes. It took about two to three years for these populations to rebound, according to Anstett.

This rapid comeback is a process biologists call evolutionary rescue, which happens when a species is able to recover from the threat of extinction by an external factor such as a drought, Anstett explained. “Evolutionary rescue occurs when the few individuals that are left have the right genetic makeup to do better than the ones that died, so they do well or thrive within these new conditions, so the population inches back from extinction,” he said.

Evolutionary rescue has been demonstrated in lab settings but researchers only had partial observations of it in the wild before: in cancer resistance in Tasmanian devils and adaptation to pollution in killifish. However, these studies did not provide full evidence that the process was taking place.

This study, Anstett said, offers rigorous evidence that evolution happened and it led to a demographic recovery. “We had a lot of information about the wildflowers’ demography and the genes, so that provided more ironclad information that ultimately evolutionary rescue was happening.”

A great indicator of drought

The scarlet monkeyflower is a perennial herb, meaning it regrows each season from the same roots. It’s pollinated by hummingbirds and can grow up to 3 feet tall and 3 feet wide.

“This plant is found in streams in California, Baja California and Southern Oregon that are often seeps of water that seasonally flow through habitat,” said Anstett. “It really requires that flowing water to complete its life cycle and then be able to grow all the way up to seed, so it’s a great indicator of drought.”

When a drought comes, Anstett explained, water stops flowing, so the plant has two choices: grow rapidly and produce flowers and seeds before the drought really takes hold — or grow much more slowly and perhaps live for another year. This latter strategy is what the wildflowers used. “What we saw was that the plants were, in fact, developing more slowly and going more towards bunkering down, living longer, growing less fast, which is called drought avoidance,” Anstett said.

(to be continued)

Translation

加州一種野花揭示了一種新近記錄的進化過程（1/2）

在加州近1,200年來最嚴重的乾旱期間，一些野花種群奇蹟般地存活了下來。研究人員表示，他們現在認為這些花依靠的是一種快速的基因演化 - 這是首次在野外記錄到這種現象。

這場乾旱發生在2012年至2015年間，造成超過1億棵樹木死亡。這是自2,000年開始的持續特大乾旱期間的一個特別殘酷的時期，而氣候變遷加劇了這場乾旱。儘管乾旱殺死了許多通常耐旱的植物，但一種生長在濕地、溪床和泉水邊的鮮紅色野花 - 猩紅猴面花 - 卻展現出了驚人的韌性。

一個研究團隊花了八年時間研究了 55 個野生花種群，這種野生花的學名是 Mimulus cardinalis，他們透過追蹤野生花的數量並對花朵的基因組進行測序，揭示了基因變化。

這項研究成果於週四發表在《科學》雜誌上。 康奈爾大學綜合植物科學學院助理教授、該研究的第一作者Daniel Anstett說道:「我們發現，由於極端乾旱，加州各地的猴面花種群數量都在下降，並且我們發現了基因組快速進化的證據」，「然後我們就能夠將這種演變的指標，與這些族群的復原並避免滅絕的能力聯繫起來」。

雖然整個物種沒有滅絕的風險，但個別猴面花族群可能面臨滅絕，其數量與族群高峰相比下降了高達90%。Anstett表示，這些族群大約花了兩到三年的時間才恢復過來。

Anstett解釋說生物學家將這種快速復甦的過程稱為 “進化拯救” ，當一個物種能夠從乾旱等外部因素造成的滅絕威脅中恢復過來時，就會發生這種情況。他說: 「當倖存的少數個體擁有比死亡個體更合適的基因組成時，進化拯救就會發生，它們能夠在新的環境中生存或繁衍，從而使族群逐漸擺脫滅絕的威脅」。

演化拯救已在實驗室環境中得到證實，但先前研究人員在野外僅對其進行過部分觀察：例如塔斯馬尼亞袋獾的抗癌能力和鱂魚對污染的適應能力。然而，這些研究並沒有提供充分的證據證明這個過程正在發生。

Anstett表示，這項研究提供了嚴謹的證據，證明演化確實發生，最終導致了族群數量的恢復。 “我們掌握了大量關於野花種群數量和基因的信息，這為我們提供了更確鑿的證據，證明進化拯救最終確實發生了。”

絕佳的乾旱指標

猩紅猴面花是一種多年生草本植物，這意味著它每年都會從同一根系重新生長。它由蜂鳥授粉，株高可達 3 英尺，株寬可達 3 英尺。

Anstett說: 「這種植物生長在加州、下加利福尼亞州和俄勒岡州南部的溪流中，這些溪流通常是季節性流經棲息地的滲水處」， 「它非常需要流動的水來完成其生命週期，並最終結籽，因此它是指示出有乾旱的絕佳植物」。

Anstett解釋說，當乾旱來臨時，水流停止，植物有兩種選擇：要么快速生長，在乾旱真正到來之前開花結籽；要么生長緩慢，或許可以再活一年。野花們選擇了後者策略。 Anstett說: 「我們觀察到，這些植物實際上發展得更慢，更傾向於固守生長模式，壽命延長，生長速度降低，這被稱為抗旱」。

（待續）

Note:

1. Tasmanian devil (袋獾) is a carnivorous marsupial of the family Dasyuridae. It was formerly present across mainland Australia, but became extinct there around 3,500 years ago; it is now confined to the island of Tasmania. The size of a small dog, the Tasmanian devil became the largest carnivorous marsupial in the world following the extinction of the thylacine in 1936. It is related to quolls, and distantly related to the thylacine. (Wikipedia)

2. Killifish (鳉鱼) are a type of small freshwater or brackish water fish, mainly belonging to the family Cyprinodontidae within the order Cyprinodontiformes. They are widely distributed in tropical and subtropical swamps, streams, and other waters in the Americas, Africa, and parts of Europe. (Baidu)