taxonID	type	description	language	source
E20887E2132BFFCDA8C59644FC7D7771.taxon	description	○ 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. 1 C; Table 3; Supporting Information, Appendix S 2). 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. 1 C; Table 3; Supporting Information, Appendix S 2), 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. 1 C; Table 3; Supporting Information, Appendix S 2), 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. 1 C; Table 3; Supporting Information, Appendix S 2), 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 S 2), confirming Eaton et al. ’ s (2016 a) 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. 2 A), 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. 2 A; Supporting Information, Appendix S 3). 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. 2 A). 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. 2 B; 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 2 B; Table 3; Supporting Information, Appendix S 2). 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 2 B; Table 3; Supporting Information, Appendix S 2). 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. 2 B; Table 3; Supporting Information, Appendix S 2). 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. 1 D; Supporting Information, Appendix S 2), 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. 1 E; Table 3; Supporting Information, Appendix S 2; 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.	en	Gwee, Chyi Yin, Eaton, James A, Garg, Kritika M, Alström, Per, Van Balen, Sebastianus (Bas), Hutchinson, Robert O, Prawiradilaga, Dewi M, Le, Manh Hung, Rheindt, Frank E (2019): Cryptic diversity in Cyornis (Aves: Muscicapidae) jungle-flycatchers flagged by simple bioacoustic approaches. Zoological Journal of the Linnean Society 186 (3): 725-741, DOI: 10.1093/zoolinnean/zlz003, URL: https://academic.oup.com/zoolinnean/article/186/3/725/5372980
E20887E2132DFFCCAB7D9511FE7E70BD.taxon	description	○ C. sumatrensis indochina Chasen & Kloss, 1928 – SE Myanmar, Thailand (except C & S), Cambodia, S Laos and C Vietnam. ○ C. sumatrensis lamprus Oberholser, 1917 – Anamba Island (off E Peninsular Malaysia). Although the Sundaic C. olivaceus is a widespread species and relatively common in Sumatra and Java, limited studies have been carried out on this jungle-flycatcher. Until recently, it was mistakenly treated as a Rhinomyias due to its seemingly different plumage in comparison to most other Cyornis species. Our bioacoustic analyses detected limited geographical variation between the Bornean and Javan populations and between the Sumatran andThai populations (Table 3). However, strong vocal differentiation is absent among the four populations (Fig. 1 F), thus supporting the taxonomic treatment of a single species. Similarly, the greater Sundanese C. caerulatus is very poorly known in life, especially the Sumatran C. c. albiventer. Although our bioacoustic analyses did not detect strong vocal distinction between the Sumatra and Sabah populations, we encountered two different song types of C. c. caerulatus: one of which is a consistent four-element phrase, while the other consists of two to three elements in a descending phrase (see Fig. 1 G). CONSERVATION IMPLICATIONS Overall, we propose taxonomic revisions to six out of the nine Cyornis species complexes in the present study, resulting in the elevation of ten taxa to species status. Our recommendation for a taxonomic elevation of C. kalaoensis generates an additional small-island endemic, but we do not believe that it would currently classify as threatened given that it is common in secondary habitat (Eaton & Rheindt, 2017). However, limiting the distribution range of C. banyumas to Java calls for an urgent need to reconsider the conservation status of this endemic species. The Javan C. banyumas population was found to be declining as a result of the bird trade (Eaton et al., 2015). The species is now very rarely encountered in the wild, and a network of Javan birders and professional bird guides only recorded the taxon a handful of times in 2018 (pers. obs.), thus the species may warrant elevation in conservation status to Critically Endangered according to criterion A 2 (IUCN, 2018). Our study demonstrates that a relatively small panel of vocal parameters can be employed as a useful tool in cryptic species detection in Cyornis flycatchers, which are characterized by great levels of hidden species diversity (Eaton et al., 2016; del Hoyo et al., 2018) and that their application was in agreement with genetic data (present data; Zhang et al., 2016; Garg et al., 2018). Using recordings collected by both professional and recreational ornithologists, and vetted by us for correct species identification (see Methods), we were able to detect vocal divergences, or a lack thereof, in various species complexes, thereby providing important taxonomic and conservation insights by flagging cryptic conservation units that may otherwise slip under the radar and face extinction threats. Despite great progress in the ongoing taxonomic revolution that incorporates bioacoustic and genomic methodologies, our study suggest knowledge gaps remain even in bird taxonomy, the best-studied animal group on Earth. Given that vocal traits are of critical importance in the maintenance of species integrity in songbirds, and can be even more appropriate for species delimitation than plumage in some groups (Rheindt et al., 2008), we propose a routine application of simple vocal parameter sets – adjusted to taxonomic grouping – to scan for additional cryptic species-level diversity across songbirds. However, we emphasize that the application of such simple standard parameter sets, whether bioacoustic or morphological (e. g. Tobias et al., 2010), can only ever serve to flag units of interest and produce provisional new treatments, but not to override well-established treatments based on integrative genomic, bioacoustic and morphological data.	en	Gwee, Chyi Yin, Eaton, James A, Garg, Kritika M, Alström, Per, Van Balen, Sebastianus (Bas), Hutchinson, Robert O, Prawiradilaga, Dewi M, Le, Manh Hung, Rheindt, Frank E (2019): Cryptic diversity in Cyornis (Aves: Muscicapidae) jungle-flycatchers flagged by simple bioacoustic approaches. Zoological Journal of the Linnean Society 186 (3): 725-741, DOI: 10.1093/zoolinnean/zlz003, URL: https://academic.oup.com/zoolinnean/article/186/3/725/5372980
