Endangered Lantau Short-legged Horned Toad may be undergoing speciation

The Short-legged Horned Toad (Boulenophrys brachykolos), listed as endangered on the International Union for Conservation of Nature Red List of Threatened Species, is the only known small frog species in Hong Kong belonging to the genus Boulenophrys of the family Megophryidae. A study led by the Division of Science at Lingnan University has found that the Lantau Island population of the Short-legged Horned Toad shows clear genetic divergence from other local populations, along with several notable differences in the mating calls of males. The research team suggests that the Lantau population represents an early stage of speciation. Geographical isolation of Lantau Island from other landmasses likely contributed to these unique evolutionary traits. The team recommends treating the Lantau population as a separate conservation unit in future. These findings have been published in international academic journal Current Herpetology.

The Short-legged Horned Toad is distributed across mountain streams on Lantau Island, Hong Kong Island, Kowloon, the New Territories, and adjacent Shenzhen. The research team, led by Lingnan University, collected 19 samples of the Short-legged Horned Toad (nine from Lantau Island, six from Hong Kong Island, and four from Kowloon) to examine their genetic and morphological characteristics. The results show that the Short-legged Horned Toads on Lantau form a distinct genetic group separate from those on Hong Kong Island, Kowloon, and Shenzhen. This suggests that the Lantau population has been separated from other populations for a considerable period.

In addition, the team recorded and analysed the mating calls of male Short-legged Horned Toads from Lantau Island, Hong Kong Island, and Kowloon. They found significant differences in their calls between Lantau Island and other local populations. The Lantau population produces calls with a faster rhythm and shorter individual notes. In terms of physical appearance, the team found no marked differences between frogs from Lantau Island and other regions, indicating that physical characteristics alone may be insufficient to distinguish the Lantau population from other populations.

Prof Jonathan Fong, Associate Dean (Administration and Education) of the Wu Jieh Yee School of Interdisciplinary Studies, and Associate Professor of the Division of Science, is the corresponding author of the study; and Prof Sung Yik-hei, Adjunct Assistant Professor of the Division of Science, is the first author.

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