Rhipidura habibiei, Rheindt & Prawiradilaga & Ashar & Lee & Wu & Ng, 2020

Rheindt, Frank E., Prawiradilaga, Dewi M., Ashar, Hidayat, Lee, Geraldine W. X., Wu, Meng Yue & Ng, Nathaniel S. R., 2020, A lost world in Wallacea: Description of a montane archipelagic avifauna (supplement), Science 36, pp. 1-104 : 8-13

SM2:

Rhipidura habibiei , species nova

(Peleng Fantail;

urn:lsid:zoobank.org:act:A2215E04-BCE0-4D4D-92F3-71C51595B033

) Frank E. Rheindt, Dewi M. Prawiradilaga, Hidayat Ashari, Suparno, Nathaniel S. R. Ng

Holotype

MZB.Ornit.34.461 ( fig. S1 ); adult female collected 22 Dec 2013 in forest above Kokolomboi village (~ 850m elevation) on Peleng Island (S 01⁰ 17.561 '; E 122⁰ 52.520 '). Collected by the Rheindt / LIPI field party, including tissue samples from breast muscle and liver; skin prepared by Suparno; field number Pel38; no molt (worn plumage); medium fat; weight 10g; wing length 6.5cm; wing spread 22cm; total length 15.8cm; bill 1.3cm; tail 8cm; tarsus 2cm.

Description of holotype

Crown, nape, ear coverts and neck sides are mid-brown (7.5YR 4/2), with a distinct cinnamon-chestnut forehead extending over eye (7.5YR 4/8). Black rictal bristles. Nape color slowly grading into warmer cinnamon-rufous (2.5YR 4/10) across mantle, scapulars and rump to the basal 60% portion of tail. The outer remiges are mostly dark dusky-brown (7.5YR 2/1), becoming paler and more olive-brown (7.5YR 4/2) towards the inner remiges. All remiges have narrow but intense rufous outer edging concolorous with rump and lower back color. The wing coverts are almost identical to the inner remiges in color, with an increasing intensity and width of bright-rufous feather tipping towards the median and lesser coverts. The distal 40% of the tail is greyish-black (N2), with paler rufous tips (5YR 5/6) on the underside only. Chin and throat form a white triangle delimited below by a conspicuous large black breast patch. A diffuse band of grey coloration (N5) with a black scaly appearance created by black feathers with narrow grey edging demarcates the black breast patch on its lower side. The belly is pale buff (7.5YR 9/8), grading into a richer, fuller hue on the flanks and undertail coverts (7.5YR 5/6). The iris is dark-brown, the bill black with a pinkish base to the lower mandible, and the tarsus on the live bird was described as pinkish- horn.

Diagnosis

A mid-sized, rufous-toned Rhipidura typical of a radiation of fantails distributed throughout Australasia. It most closely resembles R. sulaensis and R. teysmanni ( 57), and constitutes the third member of this radiation. Its plumage distinctions from the other two species are subtle yet consistent. However, the most characteristic distinction is its unique courtship vocalization (7 2).

Morphologically, the new species differs from R. sulaensis from the Sula Islands in its much narrower, less distinct rufous tips to the underside of the rectrices, in its more distinct black scaling below the black breast patch, and in its more strongly cinnamon-buff (less white) central underparts. The new species’ throat is cleaner white, less interspersed with dusky tips to the feathers.

The new species differs from all three subspecies of R. teysmanni from Sulawesi in its wider black portion of the tail and its warmer brown crown and upper mantle. When compared to the geographically most closely adjacent subspecies R. teysmanni toradja from eastern and central Sulawesi, the new species additionally differs in its cleaner white throat and slightly less conspicuous scaling below the black breast patch, while it is additionally distinguished from R. teysmanni teysmanni of the Lompobattang Massif in South Sulawesi by its blacker breast patch and by the richer chestnut (less cinnamon) coloration of its brighter body parts (such as supercilium, rear upperparts, flanks and vent).

Etymology

The new species’ epithet is in honor of the late Bacharuddin Jusuf Habibie (deceased 11 Sep 2019), the third president of the Republic of Indonesia. President Habibie was known as a keen environmentalist and contributed greatly to the science and conservation of nature in Indonesia.

Individual, sex and age-related variation within the taxon

The only three specimens (all adult; one female, two males) exhibit limited variation in terms of extent of breast patch and black mottling below breast patch that may have been caused by the preparation of the specimens.

History of discovery

The new species has doubtless been known to the local inhabitants of Peleng Island for a long time. Mochamad Indrawan was presumably the first outside ornithologist to see this new bird when encountering a dead individual during his work on Peleng in the mid-2000s and re- encountering the species in the wild on several undated occasions ( 49). During a field trip between 23-30 March 2009, FER and Filip Verbelen frequently observed the species near the type locality ( 49), where we returned from 18-23 Dec 2013 to collect the type and the accompanying individuals ( 19).

Distribution and status

The new species is restricted to montane forest on the island of Peleng, the largest landmass in the Banggai Archipelago, at elevations not lower than 750m ( 19, 49) ( fig. S2 ). Over two longer visits to the highlands of Peleng, we found that the species becomes gradually more common towards higher elevations before it seems to drop out somewhere slightly below the tallest peak on Peleng at 1,022m. The new species is replaced on Sulawesi to the west by Rhipidura teysmanni , and on the Sula Archipelago to the east by R. sulaensis . Its occurrence on other islands of the Banggai Archipelago is highly unlikely given that only one of them, the small island of Bangkulu, slightly exceeds 600m in elevation, with only 5 ha of land lying above 600m, still well below the lowest known elevational occurrence of the new species. R. habibiei must be considered threatened given the small extent of its occurrence and the continuing loss of its habitat. Only 25,071 ha of land on Peleng fall above the approximate 750m elevational cutoff, most of it formerly constituting a single contiguous block of highland forest ( fig. S2 ). However, our own observations in combination with satellite imagery indicate extensive forest loss to small-scale agriculture and logging by burgeoning village communities. Google Earth’s present coverage of the area is mixed, with large swathes covered by insufficient or outdated (e.g., 2004) imagery. However, given current satellite coverage, a conservative estimate is that 9,987 ha (~40%) from within the elevational range of R. habibiei have either been completely deforested or constitute young regrowth or unviable forest fragments surrounded by clearings. This would leave only 15,084 ha of more or less undisturbed primary or older secondary forest. Recent observations indicate, however, that this extent of forest loss is probably an underestimate. After the first discovery of this species and a number of other new bird taxa on Peleng ( 49), the island became a destination for an average of 1-3 international adventure and birdwatching tour groups per year, which considerably helped spur the local economy of the village near the type locality (name withheld). While this sort of ecotourism has a positive impact on the natural environment in many reported cases, on Peleng the sudden influx of tourist dollars led to observations of increased logging and expansion of infrastructure, prompting the rapid destruction of forest at the original type locality over the last five years. In the near future, it will be of paramount importance for the survival of Peleng’s unique montane fauna to find ways in which the influx of eco-tourism dollars can create incentives for conservation.

Taxonomic rationale

Based on its plumage coloration, the new species is clearly a member of the rusty-bellied fantail Rhipidura teysmanni radiation, hitherto known from Sulawesi and the Sula Archipelago ( 57). The discovery of a new constituent of this radiation on the Banggai Archipelago closes the geographic gap between Sulawesi and Sula. Most previous taxonomic treatises (e.g. 6 1, 7 5) have regarded all members of this radiation as conspecific, and indeed plumage differences are relatively minor and have long been interpreted as consistent with a subspecific treatment. However, recent research into patterns of bioacoustic and genomic differentiation among rusty-bellied fantails from Sulawesi, Sula and Banggai has produced strong evidence in favor of species level treatment of all three island populations (7 2).

Vocalizations: Bioacoustically, the courtship vocalization (=song) of the new species from Peleng is the most distinct of any member of the radiation. A detailed characterization of this song has been published elsewhere ( 49). In fact, when we first found the species in the field, the bird stood out through its unusual, simple descending song that lacks the typical complex tinkling quality of its congeners ( 49). Quantitative bioacoustic comparisons revealed that the unusual vocal features of the new Peleng species have led to an acoustic leapfrog pattern in rusty-bellied fantails in which the two terminal (=easternmost and westernmost) species (i.e., R. teysmanni and R. sulaensis ) are more similar to each other in courtship vocalizations but are geographically divided by the new species with its unusual song (7 2). The great vocal distinctness of the new R. habibiei is surprising because it belies its geographic proximity to R. teysmanni (Sulawesi) across a combined lowland and sea gap of less than 40km and its frequent land connection to R. sulaensis (Taliabu) across Pleistocene land bridges during times of global cooling ( 49). Vocal behavior is known to be an important feature in species cohesion and reproductive isolation in songbirds (7 6, 77), and has been shown to be more important as an indicator of species limits than plumage traits in some passerine lineages ( 78). Therefore, recent authors have accepted the unmistakable vocal uniqueness of the new Peleng fantail as an indication of its status as an undescribed new species (57, 7 2).

Genomic data: In a previously published analysis (7 2), we conducted a comparison of>11,000 genome-wide markers with a complete representation among 16 individuals spanning all three species within the rusty-bellied fantail R. teysmanni radiation. In this analysis, the new species from Peleng emerged as most closely related to R. teysmanni from Sulawesi (both subspecies teysmanni and toradja) and less closely related to R. sulaensis from Sula. This phylogenomic result is significant considering that – among all pairwise vocal comparisons – the greatest bioacoustic differentiation is found between R. teysmanni and the new species, with strong vocal distinctions in both non-courtship vocalizations and courtship songs (7 2). Therefore, the relatively shallowest genomic differentiation among the three island populations corresponds to the deepest bioacoustic divergence.

Although the new species and R. teysmanni emerged as most closely related within the radiation, comparisons of genome-wide data allow for the designation of both taxa as independent species: the basal split between R. sulaensis and the other taxa is mainly based on a genomic signal contained in ~20% of the genetic variance across study loci, whereas the second most dominant genomic signature – contained in ~14% of the genetic variance across markers – predominantly represents the deep divergence between the new species and R. teysmanni [ figure 5 in (7 2)]. The presence of a significant proportion of genomic locus cohorts displaying deep differentiation between the new species and either of its two neighbors was in agreement with gene flow analyses (‘ABBA-BABA tests’) that pointed to a history of rare introgression between the new species and its neighbors (7 2), perhaps during episodes of unusual climate forcing dispersal between islands. Such secondary introgression is not unusual among congeneric bird species ( 79) and is not in conflict with species level treatment.

Figures

Fig. S1. Holotype of Rhipidura habibiei (MZB.Ornit.34.461).

Fig. S2. Google Earth satellite map of Peleng and Banggai (top) and the western half of Taliabu (bottom). Peleng and Banggai are the two largest islands of the “Banggai Archipelago”. Our main collection site, an unnamed locality “above Kokolomboi [village]”, is mapped with a yellow pin. Areas above 800m elevation are circled with a red line, indicating the presence of montane vegetation. The island of Taliabu is the largest member of the “Sula Archipelago”. Our main collection locality “Waiyo dinahana” is mapped with a yellow pin. Areas above 1,050 m elevation are circled with a red line, indicating the presence of a peculiar montane stunted forest vegetation. Within the montane zone above 1,050m, areas degraded by logging activity as reflected on Google Earth satellite imagery are mapped in turquoise and areas burnt down by extensive fires in the 1980s are mapped in dark-green. Given the outdated status of some of the satellite imagery, present-day forest degradation is likely more extensive than shown.

Fig. S5. Mitogenomic maximum likelihood (ML) tree phylogram of relationships among the four constituent members of the Locustella castanea radiation. Identical maximum bootstrap support (100), as shown for clades surrounding L. portenta, was produced using three different tree-building methodologies: ML, maximum parsimony, and neighbor-joining. Color-coded uncorrected pairwise sequence divergences are given between L. portenta and other species. The bird illustrations are modified from Eaton et al. (57). Voucher numbers for the American Museum of Natural History (AMNH) in New York are given for toepad- derived DNA samples.