Wednesday, July 6, 2016

[Ornithology • 2016] Genome-Wide Data Help Identify An Avian Species-Level Lineage That Is Morphologically and Vocally Cryptic


Fig. 1. A) Streak-eared bulbul distribution and vocal collection localities. Distribution of the nominate blanfordi from Myanmar is denoted in red and conradi in blue. Diagonal lines denote montane areas largely uninhabited by either form, but may encompass possible areas of overlap; and C) Streak-eared bulbul blanfordi from Myanmar (© James Eaton) and conradi from Thailand (© Simon van der Meulen), respectively, with lines pointing to the approximate locality where photos were taken. 

Highlights
• We used genome-wide data to explore the Pycnonotus blanfordi complex.
• No vocal differentiation within the P. blanfordi complex.
• Pblanfordi and Pconradi differ in eye color.
• We uncovered cryptic diversity hitherto unrecognized.

The Streak-eared bulbul [Pycnonotus b. conradi] on the left, is visually similar to the Ayeyawady bulbul [Pycnonotus b. blanfordi] on the right despite having strikingly different genetic data.
Photos: Robert J Tizard (left), Thet Zaw Naing (right). 
MyanmarBiodiversity.org

Abstract
Species identification has traditionally relied on morphology. However, morphological conservatism can lead to a high incidence of cryptic species, as characters other than morphological ones can be biologically important. In birds, the combined application of bioacoustic and molecular criteria has led to an avalanche of cryptic species discoveries over the last two decades in which findings of deep vocal differentiation have usually been corroborated by molecular data or vice versa. In this study, we use genome-wide DNA data to uncover an unusual case of cryptic speciation in two species within the South-east Asian Streak-eared Bulbul Pycnonotus blanfordi complex, in which both morphology and vocalizations have remained extremely similar. Despite a considerable pre-Pleistocene divergence of these two bulbul species, bioacoustic analysis failed to uncover differences in their main vocalization, but examination of live birds revealed important differences in eye color that had been overlooked in museum material. Our study demonstrates that genome-wide DNA data can be helpful in the detection of cryptic speciation, especially in species that have evolved limited morphological and behavioral differences.

Keywords: ddRAD-Seq; Myanmar; Thailand; Speciation


Fig. 1. A) Streak-eared bulbul distribution and vocal collection localities. Distribution of the nominate blanfordi from Myanmar is denoted in red and conradi in blue. Diagonal lines denote montane areas largely uninhabited by either form, but may encompass possible areas of overlap; and C) Streak-eared bulbul blanfordi from Myanmar (© James Eaton) and conradi from Thailand (© Simon van der Meulen), respectively, with lines pointing to the approximate locality where photos were taken; D) Example sonogram of a main vocalization given by nominate blanfordi showing the succession of nine and four song elements, respectively, making up two successive song bouts; E) principal component analysis of four bioacoustic parameters on six individuals (conradi blue, blanfordi green), also showing the amount of variation explained by each principal component (PC).

Kritika M. Garg, Robert Tizard, Nathaniel S.R. Ng, Emilie Cros, Ariya Dejtaradol, Balaji Chattopadhyay, Nila Pwint, Martin Päckert and Frank E. Rheindt. 2016. Genome-Wide Data Help Identify An Avian Species-Level Lineage That Is Morphologically and Vocally Cryptic. Molecular Phylogenetics and Evolution. DOI:  10.1016/j.ympev.2016.05.028


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