手机APP下载

您现在的位置: 首页 > 在线广播 > 科学美国人 > 科学美国人地球系列 > 正文

科学美国人60秒:确保为帝王蝶种植的乳草是本地的

来源:可可英语 编辑:aimee   VIP免费外教试听课 |  可可官方微信:ikekenet
 下载MP3到电脑  批量下载MP3和LRC到手机
加载中..
5*;bHQeohJ-

;G7R8n*=)k#h|ZY22

This is Scientific American — 60-Second Science. I'm Jason Goldman.
Monarch butterflies depend on milkweed. They lay their eggs on milkweed, and their caterpillars eat only the leaves of the plant. No milkweed means no monarchs. So the best way to help declining monarch populations—and to preserve their epic, multi-generational migration—is to plant milkweed.
Seems simple, right? But the reality is far more complicated.
Milkweed is slightly toxic—the plant evolved its noxious substances to keep herbivores from chowing down on the leaves. But monarch butterflies evolved tolerance. In fact, they arm themselves with the stuff.
"Monarchs sequester these toxins as an anti-predator defense and sort of anti-parasite defense."
Louisiana State University biologist Matt Faldyn.
So, by ingesting the toxin, the caterpillars become toxic themselves. That keeps them safe—as long as they don't ingest too much of the poison. The problem is there are different types of milkweed. And one that's native to the tropics is now growing in the southern U.S. As these plants sense warming temperatures, they produce more of the toxin—so much more that the monarch butterflies begin to suffer.

*w(~WQX*YAF

帝王蝶.jpg
To gauge the threat, Faldyn and his team raised monarchs on either the non-native tropical milkweed or on a native milkweed. And they also tested the effects of current environmental conditions as well as temperatures expected for the southern U.S. by the year 2080.
Monarchs that ate native milkweed had comparable survival rates at both current and higher temperatures. But under those future warmer conditions, monarchs raised on the tropical milkweed survived at only one fifth the rate of butterflies raised under current conditions.
The monarchs could thus find themselves in what's known as an ecological trap. The butterflies seek out milkweed, but what is already the most common type of milkweed in the southern U.S. will eventually kill them.
The tropical species is prettier than the native ones, which is why many people prefer to plant it. But there's still time to change that.
"What we sort of show is that maybe there should be more of a focus on having native species to your area sort of preferentially planted in your gardens."
By switching to the native species, home gardeners across the country can each do their part to ensure that monarch butterflies will avoid fluttering their way into the ecological trap—which could be fatal.
Thanks for listening for Scientific American — 60-Second Science. I'm Jason Goldman.

tcK@Si4B|FF&TTx

AkS2AFAn1*VxR+K

w+5%]t@SqN5h@o-^87I7Dq#uliyfYmX*Y_u@Bz

重点单词   查看全部解释    
gauge [geidʒ]

想一想再看

n. 测量标准,轨距,口径,直径,测量仪器
v

联想记忆
species ['spi:ʃiz]

想一想再看

n. (单复同)物种,种类

 
toxic ['tɔksik]

想一想再看

adj. 有毒的
n. 有毒物质

联想记忆
preserve [pri'zə:v]

想一想再看

v. 保存,保留,维护
n. 蜜饯,禁猎区

联想记忆
toxin ['tɔksin]

想一想再看

n. 毒素,毒质

联想记忆
migration [mai'greiʃən]

想一想再看

n. 移民,移往,移动

 
threat [θret]

想一想再看

n. 威胁,凶兆
vt. 威胁, 恐吓

 
network ['netwə:k]

想一想再看

n. 网络,网状物,网状系统
vt. (

 
ecological [.ekə'lɔdʒikəl]

想一想再看

adj. 生态的,生态学的

 
complicated ['kɔmplikeitid]

想一想再看

adj. 复杂的,难懂的
动词complica

 

发布评论我来说2句

    英语学习推荐

    • 英语听写训练
      听写强化训练系统有听写比对,按句停顿,中文翻译、听写错词提示等特色功能.
    • 可可英语微信:ikekenet
      关注可可英语官方微信,每天将会向大家推送短小精悍的英语学习资料..

    科学美国人60秒

    可可英语官方微信(微信号:ikekenet)

    每天向大家推送短小精悍的英语学习资料.

    添加方式1.扫描上方可可官方微信二维码。
    添加方式2.搜索微信号ikekenet添加即可。