Cyornis hainanus (Ogilvie-Grant, 1900)

• C. hainanus View in CoL . Hainan jungle-flycatcher:

○ C. hainanus hainanus (Ogilvie-Grant, 1900) – C, E & S Myanmar, S China, Thailand, Laos, Cambodia and Vietnam.

○ C. hainanus klossi Robinson, 1921 – E Thailand, S Laos, E Cambodia and Vietnam.

Our bioacoustic results revealed that the taxonomically challenging C. banyumas species complex consists of at least four vocally distinct species ( Fig. 1C View Figure 1 ; Table 3; Supporting Information,Appendix S2). Unsurprisingly, the monotypic C. lemprieri from Palawan, which has sometimes been treated as part of the C. banyumas complex ( Renner et al., 2009), was found to be vocally distinct from all other members of the C. banyumas complex under the Isler Criterion ( Table 3). Among the remainder, our vocal data were unable to differentiate between C. magnirostris and the Javan nominate group (C. b. banyumas and C. b. ligus), as well as the undescribed Bornean population from Mt. Beratus ( Fig. 1C View Figure 1 ; Table 3; Supporting Information, Appendix S2), despite C. magnirostris being widely accepted as a monotypic species based on its disjunct range and significant morphometric and plumage differences ( Renner et al., 2009). However, this vocal similarity could be a plesiomorphic trait retained by these widely allopatric populations ( C. magnirostris , the Javan group and the Mt. Beratus population), which never come into contact, but are geographically separated by multiple intervening taxa that are vocally distinct. In contrast, the Indochinese whitei group (C. b. whitei , C. b. coerulifrons and C. b. lekhakuni), which overlaps with wintering populations of C. magnirostris , has evolved a distinct vocalization ( Fig. 1C View Figure 1 ; Table 3; Supporting Information, Appendix S2), perhaps aided by character displacement as suggested by Renner et al. ’s (2009) morphometric comparisons, which attested to greater differences between C. magnirostris and sympatric C. b. whitei vs. lesser differences between C. magnirostris and the allopatric Javan C. b. banyumas . This discrete vocal and morphometric differentiation between C. magnirostris and the neighbouring whitei group would support continued species status of C. magnirostris .

Both vocal and genetic data support deep divergence between the Javan nominate (C. b. banyumas and C. b. ligus) and the Indochinese whitei (C. b. whitei , C. b. coerulifrons and C. b. lekhakuni) groups ( Zhang et al., 2016). The Bornean C. b. montanus is vocally distinct from both the Javan nominate and Indochinese whitei groups ( Fig. 1C View Figure 1 ; Table 3; Supporting Information, Appendix S2), corroborated by strong plumage differences between C. b. montanus and other members of the C. banyumas species complex ( Renner et al., 2009). Based on our set of parameters, the undescribed Meratus Mts. taxon was found to be vocally distinct from all other members of the C. banyumas species complex, including from fellow Bornean C. b. montanus based on LDA (Supporting Information, Appendix S2), confirming Eaton et al. ’s (2016a) qualitative vocal impressions of pronounced bioacoustic differences from montanus and a recent demonstration of deep mtDNA divergence (3.27%) between the two ( Shakya et al., 2018). A more comprehensive study, including genome-wide DNA data and a more extensive bioacoustic analysis, is required to elucidate the taxonomic status of all three Bornean populations of the C. banyumas species complex (i.e. montanus and the undescribed populations from Mt. Beratus and the Meratus Mts.). In the meantime, we propose a provisional taxonomic treatment recognizing a total of six species on the basis of available vocal, genetic and morphological data:

• C. magnirostris Blyth, 1849 . Large jungle-flycatcher – C & E Himalayas, India and N Myanmar.

• C. lemprieri (Sharpe, 1884) . Palawan jungle-flycatcher – Palawan.

• C. banyumas . Javan jungle-flycatcher:

○ C. banyumas banyumas (Horsfield, 1821) – C & E Java.

○ C. banyumas ligus (Deignan, 1947) – W Java.

○ C. banyumas mardii (Hoogerwerf, 1962) – Panaitan Island (off W Java) .

• C. whitei . Hill jungle-flycatcher:

○ C. whitei whitei Harington, 1908 – N & E Myanmar, SC China, N Thailand, N & C Laos and N Vietnam.

○ C. whitei coerulifrons E. C. S. Baker, 1918 – S Thailand and N & C Peninsular Malaysia.

○ C. whitei lekhakuni (Deignan, 1956) – hills of S Thailand.

○ C. whitei deignani Meyer de Schauensee, 1939 – SE Thailand.

• C. montanus Robinson & Kinnear, 1928 . Dayak jungle-flycatcher – Borneo (except Meratus Mts.).

• Cyornis sp. nov. Meratus jungle-flycatcher – Meratus Mts. (SE Kalimantan) .

BIOACOUSTIC RESULTS SUPPORTED BY NOVEL MITOCHONDRIAL AND GENOMIC DATA

Our bioacoustic data hints at a vocal cline among the three subspecies of C. unicolor ( Fig. 2A View Figure 2 ), which is corroborated by shallow divergences in both mitochondrial and genomic data. The acoustic impression of songs is one of almost identical song motifs at gradually increasing pitch from northern populations towards cyanopolia in the south. Although abrupt avifaunal transitions along the Isthmus of Kra are observed in multiple bird species (Hughes et al., 2003; Dejtaradol et al., 2016), the nominate population C. u. unicolor from the drier monsoonal parts of South-East Asia is vocally and genetically undifferentiated from the Sundaic C. c. cyanopolia ( Fig. 2A View Figure 2 ; Supporting Information, Appendix S3). The most likely interpretation is that regular gene flow may occur between C. u. unicolor in the central part of the geographical distribution and the two terminal subspecies on either side ( Fig. 2A View Figure 2 ). Under this scenario, it is unsurprising that the two terminal taxa would be differentiated by one diagnosable vocal character ( Table 3), while being undifferentiated towards the central nominate taxon. In summary, we propose the following taxonomic arrangement for the C. unicolor species complex:

• C. unicolor unicolor (Blyth, 1843) – Garhwal (W Uttarakhand) and from C Nepal E in Himalayas to NE India, S China, Myanmar, Thailand (except C & S), N & C Laos and Vietnam.

• C. unicolor diaoluoensis (Cheng, Yang & Lu, 1981) – Hainan Island.

• C. unicolor cyanopolia Blyth, 1870 – Malay Peninsula, Sumatra, Java and Borneo.

According to our bioacoustic results, the highly complicated C. rufigastra species complex may consist of up to four vocally distinct populations ( Fig. 2B View Figure 2 ; Table 3): rufigastra , omissus , kalaoensis and possibly djampeanus . Our genetic and vocal data support previous suggestions to separate the forms from Sulawesi and satellite islands, leaving C. rufigastra mainly as a Greater Sundanese and Philippine species ( Fig 2B View Figure 2 ; Table 3; Supporting Information, Appendix S2). Sulawesi and its satellite islands lie in the Wallacean region, which has never been connected to the Sunda Shelf, thus high avian endemism is observed: more than 90 bird species on Sulawesi and its satellite islands are endemic, such as the maleo ( Macrocephalon maleo ), Sulawesi myna ( Basilornis celebensis ) and streak-headed white-eye ( Heleia squamiceps ). A recently discovered population on the Togian Islands ( Rheindt et al., 2014) showed little genetic and vocal divergence from omissus from the main island of Sulawesi, despite differences in habitat and – less so – phenotype ( Eaton et al., 2016 b). In contrast, strong vocal divergence between kalaoensis and all other members of the C. rufigastra species complex support the stark plumage differences of this uniquely coloured taxon, thus supporting taxonomic elevation to C. kalaoensis ( Fig 2B View Figure 2 ; Table 3; Supporting Information, Appendix S2). Inconclusive vocal patterns were observed in the Tanahjampea Island race djampeanus , which was vocally more similar to omissus , but distinguishable in one diagnosable parameter under the conservative Isler Criterion ( Fig. 2B View Figure 2 ; Table 3; Supporting Information, Appendix S2). The form djampeanus has recently been upgraded to species level, with kalaoensis as a subspecies ( Eaton et al., 2016; del Hoyo & Collar, 2018). However, pending more comprehensive results of genomic inquiries, our vocal data and the unusually bleached plumage of kalaoensis are more supportive of a treatment of kalaoensis as a separate and independent species, while djampeanus could conservatively be retained under C. omissus pending genetic data collection. In summary, we propose the following taxonomic arrangement for the C. rufigastra species complex:

• C. rufigastra . Mangrove jungle-flycatcher:

○ C. rufigastra rufigastra (Raffles, 1822) – Malay Peninsula, Sumatra and Borneo.

○ C. rufigastra karimatensis Oberholser, 1924 – Karimata Island (off SW Borneo).

○ C. rufigastra rhizophorae Stresemann, 1925 – Sebesi Island (extreme S Sumatra), Bangka, Belitung and Java .

○ C. rufigastra longipennis Chasen & Kloss, 1930 – Karimunjawa Islands (N of C Java) .

○ C. rufigastra simplex Blyth, 1870 – N Philippines.

○ C. rufigastra mindorensis Mearns, 1907 – Mindoro (NC Philippines).

○ C. rufigastra marinduquensis DuPont, 1972 – Marinduque (NC Philippines).

○ C. rufigastra philippinensis Sharpe, 1877 – C, W & S Philippines, including Palawan and Sulu Archipelago .

• C. omissus . Sulawesi jungle-flycatcher:

○ C. omissus omissus (E. J. O. Hartert, 1896) – Sulawesi.

○ C. omissus peromissus E. J. O. Hartert, 1920 – Selayar Island.

○ C. omissus subsp. nov. – Togian Islands.

○ C. omissus djampeanus (E. J. O. Hartert, 1896) – Tanahjampea Island.

• C. kalaoensis (E. J. O. Hartert, 1896) . Kalao jungle-flycatcher – Kalao Island.

BIOACOUSTIC SCANS FOR CRYPTIC SPECIES IN WIDESPREAD AND UNDERSTUDIED COMPLEXES

The geographical distribution of C. ruficauda encompasses Borneo, the Sulu Archipelago and the main Philippine island groups (Visayas and Mindanao), henceforth referred to as the main Philippine islands. Despite being lumped into a single species based on morphology ( Kennedy et al., 2000; Dickinson & Christidis, 2014; Clement, 2018), we found distinct vocal differences between the Bornean race isola , the Sulu race ocularis and the other races ( Fig. 1D View Figure 1 ; Supporting Information, Appendix S2), suggesting that the deep sea channels between Borneo and Sulu and between Sulu and the main Philippine islands have prevented gene flow among these populations during periods of global sea-level recession when more shallow neighbouring seas were exposed as land ( Bintanja et al., 2005). On the other hand, little vocal differentiation was observed between boholensi s and samarensis, reflecting the proximity of Mindanao to the Visayas during global ice ages allowing for gene flow. In conjunction with the distinct phenotypic differences among these three groups, e.g. a rufous orbital ring in ocularis ( Kennedy et al., 2000; Clement, 2018), and despite our somewhat low vocal sample size, we suggest that the C. ruficauda species complex consists of three species, supporting a previous study that found Philippine avian endemism to be severely underestimated ( Lohman et al., 2010). More sound recordings are required to include other races not analyzed in the present study and to ascertain the vocal differences observed. In addition, future research should include genetic characters to unravel the divergence dynamics and speciation mechanisms within the C. ruficauda complex. In summary, we propose the following taxonomic arrangement for the C. ruficauda species complex:

• C. ruficauda . Philippine jungle-flycatcher:

○ C. ruficauda ruficauda (Sharpe, 1877) – Basilan.

○ C. ruficauda samarensis (Steere, 1890) – Samar, Biliran, Leyte, Dinagat, E & C Mindanao .

○ C. ruficauda boholensis (Rand & Rabor, 1957) – Bohol.

○ C. ruficauda zamboanga (Rand & Rabor, 1957) – W Mindanao.

• C. ocularis (Bourns & Worcester, 1894) . Sulu jungleflycatcher – Sulu Archipelago.

• C. ruficrissa . Crocker jungle-flycatcher:

○ C. ruficrissa ruficrissa (Sharpe, 1887) – Mt. Kinabalu (N Borneo).

○ C. ruficrissa isola (Hachisuka, 1932) – Mountains of Borneo (except Mt. Kinabalu).

We found evidence of vocal divergence between South Asian C. t. tickelliae and C. t. jerdoni vs. South-East Asian C. t. sumatrensis and C. t. indochina ( Fig. 1E View Figure 1 ; Table 3; Supporting Information, Appendix S2; del Hoyo et al., 2018), which are usually considered conspecific on the basis of similar male plumages. Our findings concur with Rasmussen & Anderton (2005), who documented vocal and plumage differences, and with bioacoustic results independently obtained by Boesman (2016). It also concurs with the considerable plumage differences observed between the females of each taxon ( Rasmussen & Anderton, 2005; del Hoyo et al., 2018): females of the South-East Asian taxa have an olive head, neck and upperparts, whereas females of the SouthAsiantaxaarepaleblue,thussupportingthetaxonomic split of the South-East Asian taxa (C. t. sumatrensis and C. t. indochina) from the South Asian taxa (C. t. tickelliae and C. t. jerdoni). In summary, we propose the following taxonomic arrangement for the C. tickelliae species complex:

• C. tickelliae . Tickell’s jungle-flycatcher:

○ C. tickelliae tickelliae Blyth, 1843 – S Nepal and N, C & S India.

○ C. tickelliae jerdoni Holdsworth, 1872 – Sri Lanka.