Bioacoustics of Rhombophryne coronata

Call. The advertisement call recorded on 19 February 1994 (18: 30–19: 00 h) at Ankeniheny (air temperature 23.5 ° C) consists of a short tonal note emitted in regular call series of variable duration (Fig. 74 ). Most calls (= notes) are composed of two recognizable pulses. These two-pulse calls exhibit a remarkable and complex pattern of frequency modulation, with a distinct upward sweep corresponding to the initial pulse, followed by a downward sweep corresponding to the second pulse. In addition, an upward shift in dominant frequency is recognizable in the second pulse (Fig. 74 ). Numerical parameters of 15 analysed calls are as follows: call duration (= note duration) 68–95 ms (83 ± 7 ms); inter-call intervals within regular call series 284–331 ms (308 ± 13 ms); number of calls per call series 5–12 (9 ± 3); duration of regular call series 1641–4468 ms (3162 ± 1119 ms); dominant frequency 3488–3660 Hz (3588 ± 81 Hz), with a second prominent peak present at 7200–7400 Hz; prevalent bandwidth 1800–9500 Hz; harmonic frequency bands recognizable with approximately 3500 Hz spacing up to 19,000 Hz. Calls from the same recording ( Vences et al. 2006 CD 3, track 29) have been described by Vences and Glaw (2003 ) using a slightly different terminological scheme.

Remark . Belluardo et al. (2022 ) reported the candidate species Rhombophryne sp. Ca 13, based on specimen KU 340732 ( CRH 457; Fig. 71 A ), an adult female (containing 12 eggs ), collected on 5 January in 2015 in Vohidrazana Private Reserve ( 18.9761°S , 48.4993°E , ca. 1150 m a. s. l.), Alaotra-Mangoro Region, central eastern Madagascar , by C. R. Hutter and S. Lambert. We here refrain from treating the taxonomy of that candidate species, because (1) it is very closely related to R. coronata , (2) we have not been able to identify any morphological features that distinguish these lineages (they are extremely similar both externally and osteologically; compare Figs 72 and 73), and (3) we lack bioacoustic data from R. sp. Ca 13. Based on molecular phylogenetic data Rhombophryne coronata and R. sp. Ca 13 form a highly supported clade (Fig. 2 ). Our ASAP species delimitation retained R. sp. Ca 13 as a distinct species. However, data from the nuclear gene RAG 1 reveal haplotype sharing between Rhombophryne coronata and R. sp. Ca 13 (Fig. 4 ). Altogether, this is weak evidence for species-level distinction, and we need additional material from more sites in this area in order to clarify the taxonomy of these frogs.

Diagnosis. Within the genus Rhombophryne , R. coronata can easily be distinguished from all species except other members of the R. serratopalpebrosa species group by the presence of distinct superciliary spines. Within the R. serratopalpebrosa species group, it is unique in possession of a reduced first toe. For further distinction from R. serratopalpebrosa and R. guentherpetersi , see the diagnosis of those species, above. It can further be distinguished from R. vaventy by much smaller adult body size ( SVL 19.4–23.2 mm vs> 50 mm ), and finely granular dorsal skin (vs rugose); from R. ornata by much smaller adult body size ( SVL 19.4–23.2 mm vs up to 33.0 mm), three superciliary spines (vs two), and absence of reddish colouration on the thighs and inguinal region; from R. tany by slightly smaller adult body size ( SVL 19.4–23.2 mm vs 24.6 mm ), indistinct supratympanic fold (vs distinct), and shorter hindlimb ( HIL / SVL 1.28–1.43 vs 1.56); from R. regalis by absence of S-shaped dermal postnasal fold, superciliary spines being of roughly equal size (vs three spines differing in size: 1 st large, 2 nd medium, 3 rd diminutive), and shorter relative tibia length ( TIBL / SVL 0.35–0.39 vs 0.47–0.56); from R. diadema by superciliary spines being of roughly equal size (vs posterior-most spine being diminutive compared to the other two), smaller relative tympanum size ( TDH / ED 0.37–0.59 vs 0.59–0.64), and shorter relative tibia length ( TIBL / SVL 0.35–0.39 vs 0.44–0.46). For distinction from new species described herein, see accounts below. A detailed description of the species is given in Vences and Glaw (2003 ) but we here add more data on the variation and distribution of the species, as well as a redescription of the call.