The photo shows a Sulphur-crested Cockatoo (Cacatua galerita), a species that closely resembles the critically endangered Yellow-crested Cockatoo (Cacatua sulphurea). Photo credit: Matthew Kwan
Ecologists at the School of Biological Sciences of The University of Hong Kong (HKU) have made valuable discoveries that could transform the conservation of two iconic cockatoo species: the Sulphur-crested cockatoos and the critically endangered Yellow-crested cockatoos – with only 2,000 individuals remaining in the wild for the latter.
Until now, no whole-genome research had been conducted on either species, which were identified solely by subtle morphological differences. Through two innovative studies, the team uncovered new genetic insights, reshaping our understanding of these species and offering fresh hope for their survival amid severe threats from habitat loss and illegal trapping. These findings, recently published in high-impact scientific journals Molecular Biology and Evolution, and Molecular Ecology, will be highly influential in guiding future conservation efforts.
Triton Cockatoo reconfirmed as a distinct species after a century in obscurity
Although originally believed to be two distinct species, for over a century the Triton Cockatoo (Cacatua triton) has been thought to be the same species as the Sulphur-crested Cockatoo (Cacatua galerita) due to their similar appearance and with the distribution of the singular species including Australia and New Guinea. However, the study in Molecular Biology and Evolution, using cutting-edge genomic analysis, has reconfirmed that the Triton Cockatoo is, in fact, a distinct species occurring across the majority of New Guinea, with the Sulphur-crested Cockatoo now known to be restricted to just Australia and a very small portion of southern New Guinea.
This finding has profound implications for conservation, particularly in New Guinea where both species exist and where programmes led by the Indonesian government and NGOs aim to reintroduce surrendered pet birds into the wild on the western part of the island to counter the effects of climate change, land-use change, and poaching.
Dr Arthur SANDS, an expert on cockatoos from SBS and the main author of the study in Molecular Biology and Evolution, emphasised the importance of this distinction, he said, ‘Introducing the wrong species in the wrong place could jeopardise their long-term survival in the wild through hybridisation or competition between the Triton Cockatoo and the Sulphur-crested Cockatoo, potentially even disrupting ecosystems in the long term.’ He stressed that such reintroduction programmes must incorporate genetic data moving forward to avoid this. Recognising the Triton Cockatoo as a distinct species will now also require updates to global legislation, such as the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) which aims to protect these and many other parrot species, and may require new levels of protection being issued given the split.
The other study, in Molecular Ecology, focused on the critically endangered Yellow-crested Cockatoo (Cacatua sulphurea), native to Indonesia and East Timor, using DNA extracted from 100-year-old museum specimens to elucidate genetic diversity among subspecies. This approach, known as ‘museomics’, involves studying genetic materials from preserved specimens kept in museums, in this case across the USA and Europe. It allows researchers to gather vital biological data without disturbing the remaining endangered individuals in the wild.
A preserved Yellow-crested Cockatoo specimen, collected in 1911 and housed at the Bavarian State Collection, Munich. Specimens like this provide invaluable genetic data for conservation research. Photo credit: Arthur Sands
小葵花鳳頭鸚鵡標本，收集於 1911 年，收藏於慕尼黑巴伐利亞國家收藏。樣本為保育研究提供了寶貴的遺傳數據。照片來源：Arthur Sands
Preserved cockatoo specimens stored in wooden drawers at the Bavarian State Collection, Munich. These valuable collections serve as important resources for genetic research and conservation planning. Photo credit: Arthur Sands
鳳頭鸚鵡標本存放在慕尼黑巴伐利亞國家收藏木抽屜中的鳳頭鸚鵡標本。這些寶貴的收藏是遺傳研究和保育規劃的重要資源。照片來源：Arthur Sands
This research identified three genetically distinct groups across the Wallacean region, a biogeographical zone that lies between the Asian and Australian continental shelves, simplifying the previous classification of seven subspecies. The findings suggest that the subspecies C. s. citrinocristata may not be as distinct as previously thought and raises questions about how the isolated C. s. abbotti population ended up on a remote Indonesian island, given that cockatoos are not known for long-distance migration. These discoveries redefine the genetic structure of the Yellow-crested Cockatoo and offer new insights into its evolution and distribution.
Dr Astrid ANDERSSON, who led the study in Molecular Ecology explained, ‘One of the benefits of museomics is the ability to examine genetic data from taxa that are extinct, rare or inaccessible. In this case, it provides valuable information to inform conservation efforts, such as translocation, genetic rescue and breeding—steps that are crucial to avoid global extinction of C. sulphurea.’
Professor Juha MERILÄ, Associate Director (Ecology & Biodiversity Research Groups) and Chair Professor of SBS, who leads the research group where Drs SANDS and ANDERSSON are based, stated, ‘Accurate identification of evolutionarily significant units and species is essential for the effective management and conservation of rare and threatened species. Our research highlights the genetic diversity within and among these iconic cockatoo species and underscores the importance of incorporating genetic data into conservation planning.’
For further reference, the full research papers are available as follows:
Sands A.F., Andersson A.A., Reid K., Hains T., Joseph L., Drew A., Mason I.J., Rheindt F.E., Dingle C. and Merilä J. 2024. Genomic and Acoustic Biogeography of the Iconic Sulphur-crested Cockatoo Clarifies Species Limits and Patterns of Intraspecific Diversity. Molecular Biology and Evolution, 41(11), p.msae222. https://academic.oup.com/mbe/article/41/11/msae222/7840323
Andersson A. A., Sands A. F., Reid K., Hains T., Momigliano P., Lee J., Lee G., Rheindt F. E., Dingle C, Merilä, J. (2024). Museomic Sheds Light on Evolutionary Diversity in a Critically Endangered Cockatoo Species from Wallacea. Molecular Ecology. https://onlinelibrary.wiley.com/doi/10.1111/mec.17616?af=R
香港大學（港大）生物科學學院的生態學家近日在兩項研究中運用基因組分析技術，首次對兩種外形相似且具標誌性的鳳頭鸚鵡物種進行全基因組研究，揭示了牠們的關鍵遺傳特性；牠們包括大葵花鳳頭鸚鵡（Cacatua galerita），以及全球僅存2000隻的極度瀕危物種小葵花鳳頭鸚鵡（Cacatua sulphurea）。
研究結果最近分別發表在科學期刊《分子生物學與進化（Molecular Biology and Evolution）》和《分子生態學（Molecular Ecology）》上——研究結果不僅重塑了我們對這些物種的理解，還為保育策略提供新方向。
研究一：證實特里頓鳳頭鸚鵡為獨立物種
特里頓鳳頭鸚鵡（Cacatua triton）最初被視為與大葵花鳳頭鸚鵡（Cacatua galerita）不同的物種，但由於兩者外觀相似，在過去一世紀一直被視為分佈於澳洲和新幾內亞的同一物種。我們的團隊近日在《分子生物學與進化》發表研究，透過尖端的基因組分析技術證實，特里頓鳳頭鸚鵡為獨立的物種，主要分佈於新幾內亞，而大葵花鳳頭鸚鵡的分佈範圍只限於澳洲及新幾內亞南部的小部分地區。
此發現對鸚鵡保育具有深遠的影響，對於同時擁有這兩種鸚鵡物種的新幾內亞尤其關鍵。例如，印尼政府和非政府組織正推行將寵物鸚鵡重新引入新幾內亞西部野外的計畫，以應對氣候變遷、土地用途的改變及盜獵威脅。港大生物科學學院的鳳頭鸚鵡專家、此研究的主要作者Arthur SANDS 博士指出，確認特里頓鳳頭鸚鵡和大葵花鳳頭鸚鵡為兩種獨立物種，對此類野放保育計劃至關重要。他解釋道：「在錯誤的地方引入錯誤的物種可能會引致不同物種雜交或競爭，危及其在自然環境中的生存，甚至破壞生態平衡。因此，任何野放計畫都必須參考該物種的基因數據。」此外，特里頓鳳頭鸚鵡被識別為獨立物種後，國際法如《瀕危野生動植物種國際貿易公約》(CITES)等，均需要作出更新，亦可能要因應新物種而訂立新的保護級別。」
研究二：小葵花鳳頭鸚鵡分為三個獨立遺傳群體
團隊另一項發表在《分子生態學》的研究，重點研究原產於印尼和東帝汶的極度瀕危物種——小葵花鳳頭鸚鵡（Cacatua sulphurea）。研究利用「博物館組學（museomics）」技術，從百年歷史的博物館標本中提取DNA，以闡明不同亞種之間的遺傳多樣性。通過分析保存於美國和歐洲博物館的鸚鵡標本遺傳物質，研究人員在不用干擾野外僅存的瀕危個體的情況下，成功收集關鍵的生物數據。
這項研究發現，小葵花鳳頭鸚鵡在華萊士地區（位於亞洲和澳洲大陸架之間的生物地理區域），可劃分為三個獨立遺傳群體，這比過去認為的七個亞種更為簡單。研究結果表明，橘冠鳳頭鸚鵡（C. s. citrinocristata）可能並非獨立的遺傳種群。此外，研究結果亦帶出了一個有趣的問題 ——鸚鵡一直被視為不擅長長距離遷移的物種，那麼阿博蒂鳳頭鸚鵡（C. s. abbotti ）種群到底是如何與其他鸚鵡隔絕，最終流落至印尼的一個偏遠島嶼上？這些發現不僅重新定義了小葵花鳳頭鸚鵡的遺傳結構，也為其演化歷史和地理分佈帶來了新的啟示。
《分子生態學》研究的主要作者Astrid ANDERSSON博士解釋道：「博物館組學的好處之一是能夠提供一個渠道以研究已經滅絕、稀有或難以取得的類群的遺傳數據。在本研究中，它為保育工作提供了寶貴的信息，例如基因易位、基因拯救和繁殖計畫，這些行動對於避免小葵花鳳頭鸚鵡（C. sulphurea ）全球滅絕至關重要。」
港大生物科學學院生態學及生物多樣性研究學部副總監及講座教授Juha MERILÄ為以上研究團隊的負責人，他認為準確識別具有重要進化意義的單位和物種，對於有效管理和保護物種至關重要，他補充道：「我們的研究揭示了這些標誌性的鳳頭鸚鵡物種之間的遺傳多樣性，並強調了將遺傳數據納入保育規劃的重要性 。」
研究論文如下：
Sands A.F., Andersson A.A., Reid K., Hains T., Joseph L., Drew A., Mason I.J., Rheindt F.E., Dingle C. and Merilä J. 2024. Genomic and Acoustic Biogeography of the Iconic Sulphur-crested Cockatoo Clarifies Species Limits and Patterns of Intraspecific Diversity. Molecular Biology and Evolution, 41(11), p.msae222. https://academic.oup.com/mbe/article/41/11/msae222/7840323
Andersson A. A., Sands A. F., Reid K., Hains T., Momigliano P., Lee J., Lee G., Rheindt F. E., Dingle C, Merilä, J. (2024). Museomic Sheds Light on Evolutionary Diversity in a Critically Endangered Cockatoo Species from Wallacea. Molecular Ecology. https://onlinelibrary.wiley.com/doi/10.1111/mec.17616?af=R