Monday, May 3, 2021

[Herpetology • 2021] Limnonectes beloncioi • A New, Morphologically Cryptic Species of Fanged Frog, Genus Limnonectes (Anura: Dicroglossidae), from Mindoro Island, Central Philippines

 Limnonectes beloncioi 
 Herr, Vallejos, Meneses, Abraham, Otterholt, Siler, Rico & Brown, 2021

photo: S. L. Travers
We describe a new species of fanged frog (genus Limnonectes) from Mindoro and Semirara Islands, of the Mindoro Pleistocene Aggregate Island Complex, of the central Philippines. Although morphologically indistinguishable from its closest relative, Limnonectes acanthi, of the Palawan faunal region, the two species can be readily diagnosed on the basis of spectral (dominant frequency) and temporal (pulse number and structure) properties of their advertisement calls, and their allopatric insular geographic ranges on permanently separate geological platforms which have not been connected by dry land in the recent geological past—all of which we interpret as congruent and independent lines of evidence supporting our recognition of two independently evolving evolutionary lineages (species). Ribosomal RNA mitochondrial gene sequences were used to provide genetic identification of specimens and estimate phylogenetic relationships; genetic divergences between Palawan and Mindoro faunal regions exceed those estimated among other, uncontroversial, phenotypically distinct Philippine species with equivalent levels of allopatry and biogeographic isolation. The recognition of the new species further emphasizes the degree to which even well-studied Philippine landmasses still harbor unrecognized biodiversity, and suggests that other widespread Philippine fanged frogs should be scrutinized for non-traditional diagnostic character differences (mate-recognition signal divergence, ecological differences, larval characteristics, life-history trait variation), especially when their geographic ranges span the archipelago's permanent, deep-water trenches, which define its well-characterized Pleistocene Aggregate Island Complexes.

Fig. 7 Adult female paratype of Limnonectes beloncioi, new species (KU 335866; Field Collector No. RMB 17,605) in life
(photo: S. L. Travers).

Limnonectes beloncioi, new species
 Mindoro Fanged Frog
Rana macrodon blythi Boulenger, 1920 (partim).
Rana acanthi Taylor, 1923; Taylor and Elbel, 1958.
Rana macrodon acanthi (Inger, 1954).
Rana macrodon macrocephala (Inger, 1954) (partim: three Mindoro specimens [USNM] provisionally referred by Inger's “tentative identification” [Inger, 1954: 129]).
Rana magna acanthi (Inger, 1958).
Limnonectes (Limnonectes) acanthi Dubois, 1987 (partim).
Limnonectes cf. acanthi Evans et al., 2003; Setiadi et al., 2010; Diesmos et al., 2015.

Diagnosis and comparisons.— Limnonectes beloncioi is a medium-sized fanged frog, assigned to the genus Limnonectes (family Dicroglossidae), on the basis of its prominent, sexually dimorphic odontoid processes characteristic of the genus among other osteological synapomorphies (Inger, 1954, 1966; Emerson and Berrigan, 1993). The new species can be distinguished from all other known congeners based on a combination of its single-pulse/note advertisement call (vs. dual-pulses/note in L. acanthi from Palawan Island faunal region and PAIC landmasses), its phylogenetic position (sister to L. acanthi from Palawan PAIC; Evans et al., 2003; Setiadi et al., 2011), and its geographic distribution on Mindoro and Semirara Islands (vs. Palawan PAIC); it is the only species of Limnonectes known to occur on Mindoro and Semirara Islands and associated small satellite islands and, therefore, has no sympatric congeners.

Etymology.—We derive the specific epithet, a patronym, to honor the Philippine army scout and freedom fighter Esteban Beloncio, who contributed substantially to the armed resistance against the Japanese WWII occupation of Mindoro Island, 1942–1945.
 Suggested common name = Mindoro Fanged Frog.

Fig. 8 Typical appearance of forested habitat of  Limnonectes beloncioi, new species, near Sablayan Prison and Penal Farm, Mindoro, Philippines
 (photo: S. L. Travers).

Distribution.—Limnonectes beloncioi is known only from Mindoro and Semirara Islands, central Philippines (Fig. 1). Minor land-bridge and deep-water islands to the east and southwest of Mindoro have not yet been surveyed for herpetofauna; as such, the identity of any populations of Limnonectes that might eventually be discovered on Ilin, Sibay, Ambulong, Caluya, Maestre de Campo, and/or the Cuyo Islands group cannot yet be confirmed. The genetic identification of populations of Limnonectes on Busuanga, Coron, and Culion (currently considered L. acanthi [Taylor, 1923, 1928; Inger, 1954; Brown and Alcala, 1970; Diesmos et al., 2015]; thus, we anticipate these populations will be more closely related to Palawan Island L. acanthi than to L. beloncioi) would be of particular interest to herpetologists, biogeographers, and speciation geneticists (Esselstyn et al., 2010; Brown et al., 2013).

Mark W. Herr, Johana Goyes Vallejos, Camila G. Meneses, Robin K. Abraham, Rayanna Otterholt, Cameron D. Siler, Edmund Leo B. Rico and Rafe M. Brown. 2021. A New, Morphologically Cryptic Species of Fanged Frog, Genus Limnonectes (Amphibia: Anura: Dicroglossidae), from Mindoro Island, Central Philippines. Ichthyology & Herpetology. 109(1); 188-210. DOI: 10.1643/h2020095