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全球蜂群大衰退 科學家揭南瓜蜂族群逆勢成長的秘密

2023年04月18日
環境資訊中心外電；姜唯 翻譯；許祖菱、林大利 審校；稿源：ENS





https://live.staticflickr.com/65535/52816619224_0bd3d62ba1_b.jpg
停留在南瓜花上的南瓜蜂（Pruinose Squash Bees）圖片來源：Ilona Loser（CC BY-SA
4.0）



新研究首次證明農業會改變野生授粉昆蟲的演化，並影響糧食安全。

南瓜蜂僅分布於美洲，在墨西哥的數量最多。在過去，南瓜蜂的主要花粉來源是油瓜（
Buffalo Gourd）。這種棒球大小的南瓜生長在墨西哥和美國西南部的沙漠中。



羅培茲烏勒比解釋，因北美各地廣泛地種植南瓜，讓南瓜蜂棲地擴張，數量也跟著激增。
如今，南瓜蜂已經遍布美國和加拿大東南部，遠遠超出了它最初的食物來源範圍。

https://live.staticflickr.com/65535/52821688178_06d992d61c_b.jpg
野生南瓜馴化後產生各種不同的南瓜，不僅成為桌上的佳餚，更與傳統習俗緊密結合。圖
片來源：Birgit／Pixabay

為了研究南瓜屬作物對南瓜蜂演化的影響，研究人員先進行基因組定序，檢查其遺傳結構
，以了解不同族群內部和族群間遺傳多樣性的數量和分，藉以尋找其適應的特徵。

羅培茲烏勒比解釋，遺傳多樣性變少可能代表著「選擇性清除」（selective sweep），
這是有益的新突變基因頻率增加、並且逐漸固定下來的過程。

研究人員發現，蜜蜂從沙漠中的野生寄主植物轉到溫帶農業棲息地後，基因組某些遺傳多
樣性大幅減少。這種轉變可能與選擇性清除相關。



羅培茲烏勒比說，馴化南瓜屬植物的花朵氣味比野生南瓜更簡單。南瓜蜂很可能適應了農
業棲息地的新感官環境，所以活動範圍變大，族群量也明顯增加。

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 為食物銀行計畫到田裡挑選南瓜（squash）圖片來源：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
賓州州立大學昆蟲系副教授 Margarita Lopez-Uribe。圖片來源：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.”

※ 全文及圖片詳見：ENS

https://ens-newswire.com/squash-bee-populations-growing-fast-while-other-bees-fail/



https://e-info.org.tw/node/236532






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※ 作者: NEDYA 2023-04-20 09:11:20
※ 文章代碼(AID): #1aG94_cZ (Gossiping)
※ 文章網址: https://www.ptt.cc/bbs/Gossiping/M.1681953087.A.9A3.html

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