A striking new species of leaf warbler from the Lesser Sundas as uncovered through morphology and genomics

Abstract

Leaf warblers (Aves; Phylloscopidae) are a diverse clade of insectivorous, canopy-dwelling songbirds widespread across the Old World. The taxonomy of Australasian leaf warblers is particularly complex, with multiple species-level divergences between island taxa in the region requiring further scrutiny. We use a combination of morphology, bioacoustics, and analysis of thousands of genome-wide markers to investigate and describe a new species of Phylloscopus leaf warbler from the island of Rote in the Lesser Sundas, Indonesia. We show that this new Rote Leaf Warbler is morphologically and genomically highly distinct from its congenerics, but do not find vocal differentiation between different island taxa. We discuss the behaviour and ecology of this highly distinctive new species, and make recommendations about its conservation status. We believe this constitutes the first description of a novel bird species that is partly based on insights from massive amounts of genome-wide DNA markers.

Speciation in the Karamoja Apalis Apalis karamojae

“…While the standard taxonomic case in an integrative assessment would seek complementary differences in morphology, voice and genetics, nonetheless there are some species that have long been separated but evolved only minimal vocal differences, e.g. a multitude of species in the genus Zosterops (Pearson & Turner 2017), Rote Leaf Warbler Phylloscopus rotiensis (Ng et al 2018) and the Calliope rubythroats (Liu et al 2019), while few species are known that separated very recently but diverged significantly in voice, as in the special case of brood-parasitic Vidua indigobirds (Sefc et al 2005). In the present case, we have to express the view that, even if A. karamojae and A. stronachi were to be found to be genetically near-identical, we would be reluctant to accept that they could be considered conspecific under the Biological Species Concept, given the strong reproductive barriers that their songs represent.…”

“…While the standard taxonomic case in an integrative assessment would seek complementary differences in morphology, voice and genetics, nonetheless there are some species that have long been separated but evolved only minimal vocal differences, e.g. a multitude of species in the genus Zosterops (Pearson & Turner 2017), Rote Leaf Warbler Phylloscopus rotiensis (Ng et al . 2018) and the Calliope rubythroats (Liu et al .…”

The formation of the Indo-Pacific montane avifauna

“…Populations are essentially sedentary and montane apart from a few populations that reach the lowlands on small islands. The complex is probably monophyletic, but a comprehensive phylogenetic analysis is lacking (though see Jones & Kennedy, 2008; Alström et al, 2018; Ng et al, 2018; Rheindt et al, 2020). Species limits within the group are unclear, and treatment by different taxonomic authorities varies significantly.…”

“…Alignments were then further filtered by identifying and removing long-branch taxa using TreeShrink (v.1.3.3; Mai & Mirarab, 2018), followed by a final round of MAFFT, BMGE, and RAxML-NG. The final set of gene trees were analyzed in ASTRAL III v5.6.3 (Zhang et al, 2018) to produce an estimate of a species tree. In addition, all individual gene alignments were concatenated (a total of 9,295,039 bp) and a phylogeny was estimated with RAxML-NG using the GTRI+I+G model.…”

Full Issue

“…In recent years knowledge regarding the taxonomy, distribution and conservation status of the region's species has improved via significant new field and museum-based research (e.g. Indrawan et al 2006, Martin et al 2012, Reeve et al 2015, Bashari & Arndt 2016, Verbelen et al 2017, Monkhouse et al 2018, Ng et al 2018, O'Connell 2019, Irham et al 2020) and efforts to organise citizen science data such as eBird (https://ebird.org/home). These advances have been compiled in a new regional field guide (Eaton et al 2016(Eaton et al , 2021 and informed the growing Birds of the world (https://birdsoftheworld.org/bow/home) online database of the world's avifauna.…”