全球蜂群大衰退 科学家揭南瓜蜂族群逆势成长的秘密
2023年04月18日
环境资讯中心外电；姜唯 翻译；许祖菱、林大利 审校；稿源：ENS
受到杀虫剂、病原体和气候变迁等因素影响，蜜蜂这类授粉昆虫的数量正大量减少，但有
一种蜂却能逆势增加。由于北美在近1000年大量种植各类南瓜、瓠瓜，喜爱这些瓜类的南
瓜蜂（Squash Bee，学名：Eucera pruinosa）数量跟着上扬。
由宾州州立大学（Pennsylvania State University）科学家主持、4月3日刚在《美国国
家科学院院刊》（Proceedings of the National Academy of Sciences）发表的研究指
出，南瓜蜂随着南瓜属植物大量种植而跟着演化。
https://live.staticflickr.com/65535/52816619224_0bd3d62ba1_b.jpg
停留在南瓜花上的南瓜蜂（Pruinose Squash Bees）图片来源：Ilona Loser（CC BY-SA
4.0）
宾州州立大学昆虫学副教授罗培兹乌勒比（Margarita López-Uribe）说，一般谈到农业
扩张会增加哪些昆虫时，大多会想到飞蛾、苍蝇和甲虫这类害虫。集约农业会对授粉益虫
产生什么影响？我们所知甚少。透过这篇研究，我们得知农业可以增加南瓜蜂的族群规模
。日后或许能在其它授粉昆虫上发现类似现象。
新研究首次证明农业会改变野生授粉昆虫的演化，并影响粮食安全。
南瓜蜂仅分布于美洲，在墨西哥的数量最多。在过去，南瓜蜂的主要花粉来源是油瓜（
Buffalo Gourd）。这种棒球大小的南瓜生长在墨西哥和美国西南部的沙漠中。
南瓜、玉米和豆类是美洲原住民的重要作物。5000年前，北美东部林地的原住民开始驯化
油瓜的近亲美国南瓜（C.pepo），之后开始产出各类南瓜，并在3000年前开始大量种植。
1000年前，南瓜随着玉米的引入变得更加普遍。
罗培兹乌勒比解释，因北美各地广泛地种植南瓜，让南瓜蜂栖地扩张，数量也跟着激增。
如今，南瓜蜂已经遍布美国和加拿大东南部，远远超出了它最初的食物来源范围。
https://live.staticflickr.com/65535/52821688178_06d992d61c_b.jpg
野生南瓜驯化后产生各种不同的南瓜，不仅成为桌上的佳肴，更与传统习俗紧密结合。图
片来源：Birgit／Pixabay
为了研究南瓜属作物对南瓜蜂演化的影响，研究人员先进行基因组定序，检查其遗传结构
，以了解不同族群内部和族群间遗传多样性的数量和分，藉以寻找其适应的特征。
罗培兹乌勒比解释，遗传多样性变少可能代表着“选择性清除”（selective sweep），
这是有益的新突变基因频率增加、并且逐渐固定下来的过程。
研究人员发现，蜜蜂从沙漠中的野生寄主植物转到温带农业栖息地后，基因组某些遗传多
样性大幅减少。这种转变可能与选择性清除相关。
选择性清除可能会影响蜜蜂化学感知（chemosensation）相关的基因变化。化学感知指的
是生物的神经系统感知环境化学讯号的能力。以南瓜蜂来说，就是其解读花朵产生的气味
化合物的能力。
罗培兹乌勒比说，驯化南瓜属植物的花朵气味比野生南瓜更简单。南瓜蜂很可能适应了农
业栖息地的新感官环境，所以活动范围变大，族群量也明显增加。
Squash Bee Populations Growing Fast While Other Bees Fail
UNIVERSITY PARK, Pennsylvania, April 4, 2023 (ENS)
Numbers of bees and other pollinator species have declined worldwide, as
these insects suffer due to pesticides and pathogens, likely amplified by
climate change. Yet one bee species is showing rapid population expansion.
The keys to this insect’s success are its attraction to pumpkins, zucchinis,
marrows and gourds, and the massive increase in cultivation of these crops
across North America over the last 1,000 years.
https://live.staticflickr.com/65535/52816896878_3f6f88d16a_b.jpg
Kirby Smith 为食物银行计画到田里挑选南瓜（squash）图片来源：Oklahoma
Association of Conservation Districts
A new study, led by scientists at Pennsylvania State University and published
April 3 in the journal “Proceedings of the National Academy of Sciences,”
found that the specialized squash bee, Eucera pruinosa, has evolved in
response to intensifying cultivation of squashes in the genus Curcurbita.
Many different cucurbits are consumed around the world, and the majority of
the plants are medicinally valuable.
“When we think of insects benefiting from and adapting to widespread
agriculture, we tend to think of pests such as certain kinds of moths, flies
and beetles,” said Margarita López-Uribe, associate professor of entomology
at Penn State. “But the impact of agricultural intensification on the
evolution of beneficial pollinators is poorly understood. We found that
agriculture facilitated increases in population size of this squash bee, and
this may be the case for other insect pollinators, as well.”
The research is the first to demonstrate the role of agriculture as an
evolutionary force acting on a wild insect pollinator and may have
implications for food security.
https://live.staticflickr.com/65535/52816875228_fc5a85c8c2_b.jpg
宾州州立大学昆虫系副教授 Margarita Lopez-Uribe。图片来源：Lopez-Uribe Lab
Squash bees are found only in the Americas and the greatest number of species
is in Mexico. Historically, the squash bee’s primary source of pollen was
the wild buffalo gourd, Curcurbita foetidissima, a baseball-sized squash that
grew in the deserts of Mexico and the southwestern United States.
As one of the “Three Sisters,” which includes corn and beans, squash was an
important crop of Indigenous Peoples in the Americas, and around 5,000 years
ago, Indigenous Peoples of the Eastern Woodlands began to domesticate a
relative of C. foetidissima, called C. pepo.
Widespread cultivation of the resulting crops – which included pumpkins,
squash, and gourds – began later, around 3,000 years ago, and was
intensified around 1,000 years ago with the introduction of corn, also called
maize, to the agricultural systems of North America.
“By planting squash all over North America, humans created habitat for the
squash bee, and that allowed its population to explode,” said López-Uribe.
“Today, the squash bee occurs throughout the United States and southeastern
Canada – far beyond the range of its original food source.”
To investigate the evolution of the squash bee in response to the
intensification of Curcurbita agriculture, the team sequenced the bee’s
genome, examined its genetic structure – the amount and distribution of
genetic diversity within and among the bee’s various populations – and
searched for signatures of adaptation.
Decreases in genetic diversity, explained López-Uribe, can indicate “
selective sweeps,” the process by which new beneficial mutations increase in
frequency and become fixed.
The researchers found that the bee’s transition from wild host plants in
deserts to temperate agricultural habitats was associated with selective
sweeps resulting in substantial reductions in genetic diversity in some parts
of the genome.
Particularly linked to these selective sweeps were changes in genes
associated with chemosensation – the translation of chemical signals from
the environment to neurological signals that can be interpreted by an
organism. In the case of the squash bee, chemosensation refers to its ability
to interpret odor compounds produced by flowers.
“Domesticated Curcurbita plants produce floral blends that are simpler than
those of the wild Curcurbita plant,” said López-Uribe. “It is likely that
E. pruinosa adapted to a new sensory environment in agricultural habitats,
which enabled it to expand its range and significantly increase its
population size.”
※ 全文及图片详见：ENS
https://ens-newswire.com/squash-bee-populations-growing-fast-while-other-bees-fail/
https://e-info.org.tw/node/236532