Limestone Wren-Babbler (2 Viewers)

[Ben Wielstra]

The interplay of color and bioacoustic traits in the differentiation of a Southeast Asian songbird complex

Gwee ... Reindt in press Molecular Ecology

Abstract
Morphological traits have served generations of biologists as a taxonomic indicator, and have been the main basis for defining and classifying species diversity for centuries. A quantitative integration of behavioural characters, such as vocalizations, in studies on biotic differentiation has arisen more recently, and the relative importance of these different traits in the diversification process remains poorly understood. To provide a framework within which to interpret the evolutionary interplay between morphological and behavioral traits, we generated a draft genome of a cryptic Southeast Asian songbird, the Limestone Wren‐babbler Napothera crispifrons. We re‐sequenced whole genomes of multiple individuals of all three traditional subspecies and of a distinct leucistic population. We demonstrate strong genomic and mitochondrial divergence among all three taxa, pointing to the existence of three species‐level lineages. Despite its great phenotypic distinctness, the leucistic population was characterized by shallow genomic differentiation from its neighbor, with only a few localized regions emerging as highly‐diverged. Quantitative bioacoustic analysis across multiple traits revealed deep differences especially between the two taxa characterized by limited plumage differentiation. Our study demonstrates that differentiation in these furtive songbirds has resulted in a complex mosaic of color‐based and bioacoustic differences among populations. Extreme color differences can be anchored in few genomic loci and may therefore arise and subside rapidly.

 

[Peter Kovalik]

The interplay of color and bioacoustic traits in the differentiation of a Southeast Asian songbird complex

Gwee ... Reindt in press Molecular Ecology

Abstract
Morphological traits have served generations of biologists as a taxonomic indicator, and have been the main basis for defining and classifying species diversity for centuries. A quantitative integration of behavioural characters, such as vocalizations, in studies on biotic differentiation has arisen more recently, and the relative importance of these different traits in the diversification process remains poorly understood. To provide a framework within which to interpret the evolutionary interplay between morphological and behavioral traits, we generated a draft genome of a cryptic Southeast Asian songbird, the Limestone Wren‐babbler Napothera crispifrons. We re‐sequenced whole genomes of multiple individuals of all three traditional subspecies and of a distinct leucistic population. We demonstrate strong genomic and mitochondrial divergence among all three taxa, pointing to the existence of three species‐level lineages. Despite its great phenotypic distinctness, the leucistic population was characterized by shallow genomic differentiation from its neighbor, with only a few localized regions emerging as highly‐diverged. Quantitative bioacoustic analysis across multiple traits revealed deep differences especially between the two taxa characterized by limited plumage differentiation. Our study demonstrates that differentiation in these furtive songbirds has resulted in a complex mosaic of color‐based and bioacoustic differences among populations. Extreme color differences can be anchored in few genomic loci and may therefore arise and subside rapidly.

Gypsophila crispifrons, Gypsophila annamensis, Gypsophila calcicola

IOC Updates Diary Dec 12 Accept proposed split of Limestone Wren-Babbler into three species with English name changes.

 

[Peter Boesman]

I had a look at the bioacoustic analysis because I was surprised the short song strophes of calcicola weren't identified as a diagnostic character for this taxon, as in my earlier brief analysis (see Birds of the World ).

It seems that a few errors in the paper masked this vocal difference:

• AV15336 was wrongly assigned to annamensis instead of calcicola (see AVoCet : Recording of Limestone Wren-babbler, Gypsophila crispifrons (msu.edu) )
• ML71225 and ML71226 are in my opinion clearly duets and should have been excluded from the sample set

By applying these two corrections, one gets for their measurements in Table S2:
Song phrase duration
crispifrons combined: 4.02-11s
calcicola: 0.71-1.69s
annamensis: 2.31-7.44s

This would clearly have made a different PCA graph separating calcicola from the other two.
The remark about mutual exclusive vocal or morphological difference is then probably erroneous as well.

This being said, this correction only further supports the treatment of calcicola as a distinct taxon which deserves species status, not only because of genetic and morphological difference, but also because of its short song phrases.

 

[DMW]

I had a look at the bioacoustic analysis because I was surprised the short song strophes of calcicola weren't identified as a diagnostic character for this taxon, as in my earlier brief analysis (see Birds of the World ).

It seems that a few errors in the paper masked this vocal difference:

• AV15336 was wrongly assigned to annamensis instead of calcicola (see AVoCet : Recording of Limestone Wren-babbler, Gypsophila crispifrons (msu.edu) )
• ML71225 and ML71226 are in my opinion clearly duets and should have been excluded from the sample set

By applying these two corrections, one gets for their measurements in Table S2:
Song phrase duration
crispifrons combined: 4.02-11s
calcicola: 0.71-1.69s
annamensis: 2.31-7.44s

This would clearly have made a different PCA graph separating calcicola from the other two.
The remark about mutual exclusive vocal or morphological difference is then probably erroneous as well.

This being said, this correction only further supports the treatment of calcicola as a distinct taxon which deserves species status, not only because of genetic and morphological difference, but also because of its short song phrases.

This is perhaps a salutory lesson. I raised this potential issue with the xeno canto mods in relation to restricted access recordings, following an experience with a misidentified restricted recording. At least with the open access recordings on xc, there's a possibility that somebody will recognise the error and flag the recording.
I did wonder whether this might ultimately result in an erroneous publication, and it's fortunate that here the apparent errors weren't consequential.

 

[Peter Boesman]

I contacted the authors, and after some discussion we reached the following outcome:

• AV15336: while in the suppl. inf. table S2 it is listed under annamensis, this was an editing error and it was correctly included in the calculations
• ML71225 and ML71226 and others: My position is that calcicola’s song (= uttered by a single bird and often with identical repeats) is unique in being so short, none of the other two races ever uttering such a short song phrase. Their position is that song and duet should/can be treated together, masking what I call the ‘unique short song’, and thus no clear vocal difference between calcicola and annamensis is found.

In other words, depending on what one calls homologous vocalizations, the outcome is different.

While we didn't reach an agreement on the best approach, at least now we know why we reached different conclusions

But, as mentioned before, if my approach is followed, this only strengthens further the support for the distinctiveness of the three taxa.

 

[njlarsen]

So in other words you have a basis for a paper describing your way of analyzing it and your conclusions.

Niels

 

[Peter Boesman]

So in other words you have a basis for a paper describing your way of analyzing it and your conclusions.

Let's say that when more sound recordings become available and a bit more field study is done about vocal behaviour of these birds, it is worthwhile to publish a more robust bioacoustic analysis.
(At present only a handful of recordings was available to the authors, and I may add that an unknown number of these is of excited birds right after playback)

My main criticism to the vocal analysis in the paper is that although it is acknowledged that birds have a song and a duet, these two vocalizations are just mixed in the analysis. By not discriminating, you can't obviously find any differences.
While some will say it is scientifically correct to describe your method and then report the results of your analysis, I think the choice of the method is not compatible with the aim of the analysis, which is to investigate whether there are any vocal differences.

Future will tell which was the better approach... (at least if all three taxa manage to survive, as I understand the future of calcicola is not too bright)