Sat, Dec 05, 2015 page3

• Iconic butterfly ‘migrated’ to Taiwan

  • By Chen Wei-han / Staff reporter
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  The Agehana maraho, a swallowtail butterfly species endemic to Taiwan, originated from North America and later dispersed throughout East Asia between 23.03 and 5.33 million years ago, researchers said yesterday.

  It was previously believed that the species, commonly referred to as the broad-tailed swallowtail butterfly, belonged to an Asian butterfly genus native to China.

  Recognized as Taiwan’s “national butterfly” and known for its rear-protruding hind wings and red crescent mottles, the butterfly is one of only two species of the genus Agehana — the only class of the Papilionidae family that is native to East Asia.

  The other species is the Agehana elwesi, a continental butterfly endemic to southern China.

  Discovered and named by Japanese entomologist Shonen Matsumura in 1936, the broad-tailed swallowtail butterfly had been considered to be closely related to the Agehana elwesi — to the extent that the butterfly’s status as an independent species had been disputed for more than 70 years, until Taiwanese researchers identified the distinct genetic differences between the continental and insular swallows in 2009 using molecular DNA testing, the Bureau of Forestry said.

  A team led by National Taiwan University professor Wu Li-wei (吳立偉), National Taiwan Normal University professor Hsu Yu-feng (徐堉峰) and National Sun Yat-sen University professor Yen Sheng-hung (顏聖紘) sampled four specific genes from a total of 86 species within the Papilionidae family to reconstruct their phylogenetic relationships and historical scenarios.

  The team discovered that the genus Agehana actually falls within the American Papilio subgenus Pterourus and is not as previously suggested phylogenetically close to the Asian Papilio subgenus Chilasa, which explains the great morphological distinction of the Agehana from other Asian butterflies, the team said.

  The team inferred from the dating and biogeographic analysis that an American ancestor of Pterourus was distributed to East Asia in the early Miocene period via the Bering Land Bridge — which connected Asia and North America at various times during the Pleistocene ice ages — and developed into the Agehana genus, resulting in the present “East Asia-America” disjunction distribution.

  The broad-tailed swallowtail butterfly is classified as an endangered species in Taiwan and listed on the International Union for Conservation of Nature’s red list of threatened species, the bureau said.

  The butterfly only feeds on Sassafras randaiense, a vulnerable species of laura tree native to Taiwan that is sparsely distributed across the nation’s Central Mountain Range, it said.

  The butterfly’s scientific name “maraho” was derived from the Atayal language, meaning “chieftain” or “leader,” suggesting the unparalleled status of the broad-tailed swallowtail among Taiwan’s butterflies, the bureau said, adding that it has designated 55,991 hectares of forest in Hsinchu County’s Wufeng Township (五峰) and Miaolin County’s Taian Township (泰安) as the butterfly’s conservation area.
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