Myanmar (20/06/16) - Experts from (WCS) Wildlife Conservation Society and the National University of Singapore (NUS) have made a surprising discovery that could subvert the significance of traditional criteria used for species classification.
Employing novel techniques to retrieve DNA sequences from thousands of genomic locations, the researchers were able to uncover an unusual case of cryptic speciation in the Streak-eared bulbul [Pycnonotus blanfordi], a bird widespread throughout South-east Asian countries.
Cryptic speciation produces closely related sister species that are very similar in appearance and often overlooked by scientists until genetic and/or bioacoustic inquiries reveal species-level differences.
Traditionally, the bird identification literature has relied on shape and plumage color to classify bird species. More recently, vocalizations have also been used to uncover cryptic species otherwise similar in body appearance.
In the last two decades, DNA sequence comparison has gradually been added as a tool in the kit for species delimitation, casting light on a number of cryptic species where neither morphological nor bioacoustic differences provided clues for species differentiation.
"Distinguishing different species is a non-trivial task of great importance," said Colin Poole, WCS Regional Director for the Greater Mekong region. "This research helps us better understand the evolution of life and often points to cases in which science has hitherto underestimated the extent of actual species diversity present in any given region."
The Streak-eared bulbul [Pycnonotus blanfordi conradi] on the left, is visually similar to the Ayeyawaddy bulbul [Pycnonotus blanfordi blanfordi] on the right despite having strikingly different genetic data. Photo (c) Robert Tizard (left), Thet Zaw Naing (right).
After careful examination, two described subspecies of Streak-eared bulbul [Pycnonotus blanfordi] resident in Myanmar [P. b. blanfordi] and Thailand/Indochina [P. b. conradi] were found to exhibit deep genome-wide differentiation indicating they are two separate species.
Despite negligible nuances in the birds' plumage color, and limited differentiation in their vocalizations, WCS and NUS ornithologists identified a surprising genetic divergence dating back as far as the early Pleistocene.
A closer look also revealed different eye colors between the two forms, which the scientists believe to be an important morphological differentiating trait in mate recognition and reproductive isolation, prompting them to call for an elevation of both forms to species level, and naming the one specific to Myanmar “Ayeyawady bulbul”.
"Cryptic species have always represented an intriguing challenge for scientists," explains Dr. Robert Tizard from WCS Myanmar. "Advancements in DNA methodologies are of tremendous help in understanding the rich biodiversity of Myanmar and tropical Asia.”
Through this discovery, scientists at WCS and NUS have demonstrated how novel DNA sequencing technologies that retrieve genome-wide DNA can be put to use in species delimitation, and advocate for more systematic use of genome-wide DNA for the detection of cryptic species.
“Even in birds, which are better-known than most other living beings, the age of new species discoveries is not over,” said Dr. Frank Rheindt from NUS. “We hope that future collaborations between academia and conservation NGOs will lead to the discovery of numerous additional cryptic species to help us obtain a more realistic understanding of true levels of species diversity.”
Although Streak-eared and Ayeyawady bulbuls are generally common where they occur and neither of the cryptic species involved in this discovery seem to be under threat of extinction, the future discovery of cryptic species may well refer to endangered species that will require immediate conservation action.
To read the full research paper on the current issue of Molecular Phylogenetics and Evolution journal, click here. “Genome-wide data help identify an avian species-level lineage that is morphologically and vocally cryptic,” appears in the journal, Molecular Phylogenetics and Evolution. Authors include: Kritika M. Garg of NUS, Robert Tizard of WCS, Nathaniel S.R.Ng of NUS, Emilie Cros of NUS, Ariya Dejtaradol of University of Ulm, Germany and Prince of Songkla University, Thailand, Balaji Chattopadhyay of NUS, Nila Pwint of Nature and Wildlife Conservation Division, Myanmar, Martin Päckert of Senckenberg Natural History Collections and Frank E. Rheindt of NUS.
This work was supported by The Leona M. and Harry B. Helmsley Charitable Trust.
WCS (Wildlife Conservation Society)
MISSION: WCS saves wildlife and wild places worldwide through science, conservation action, education, and inspiring people to value nature. To achieve our mission, WCS, based at the Bronx Zoo, harnesses the power of its Global Conservation Program in nearly 60 nations and in all the world’s oceans and its five wildlife parks in New York City, visited by 4 million people annually. WCS combines its expertise in the field, zoos, and aquarium to achieve its conservation mission. Visit: newsroom.wcs.org Follow: @WCSMyanmar. For more information: 347-840-1242.
National University of Singapore (NUS)
A leading global university centred in Asia, the National University of Singapore (NUS) is Singapore’s flagship university, which offers a global approach to education and research, with a focus on Asian perspectives and expertise.
NUS has 16 faculties and schools across three campuses. Its transformative education includes a broad-based curriculum underscored by multi-disciplinary courses and cross-faculty enrichment. Over 37,000 students from 100 countries enrich the community with their diverse social and cultural perspectives.
NUS has three Research Centres of Excellence (RCE) and 26 university-level research institutes and centres. It is also a partner in Singapore’s fifth RCE. NUS shares a close affiliation with 16 national-level research institutes and centres. Research activities are strategic and robust, and NUS is well-known for its research strengths in engineering, life sciences and biomedicine, social sciences and natural sciences. It also strives to create a supportive and innovative environment to promote creative enterprise within its community.
This year, NUS celebrates its 110th year of founding together with Singapore’s 50th year of independence. As the island’s first higher education institution established by the local community, NUS prides itself in nurturing generations of leaders and luminaries in Singapore and Asia.
For more information on NUS, please visit www.nus.edu.sg. Details on NUS’ 110th Anniversary celebrations are available at nus110.sg.