Wednesday, June 27, 2018

[Herpetology • 2018] Amolops gerutu & A. australis • Elevational Size Variation and Two New Species of Torrent Frogs (Anura: Ranidae: Amolops Cope) from Peninsular Malaysia


[A, C]  Amolops larutensis (Boulenger, 1899)
[B, D] Amolops gerutu 
Chan, Abraham, Grismer & Grismer, 2018

  (A) female Amolops larutensis from Fraser's Hill, Pahang; (B) female A. gerutu from Chemerong, Pahang;
 (C) male A. larutensis from Fraser's Hill; (D) male A. gerutu from Sekayu, Terengganu;


Abstract
Previously, only one species of torrent frog (Amolops larutensis) was thought to occur throughout Peninsular Malaysia. However, genomic work has demonstrated that populations from eastern Peninsular Malaysia form two separate lineages that are genetically distinct from A. larutensis that is now restricted to the western half of Peninsular Malaysia. This study demonstrates that all three lineages can be morphologically distinguished from each other, thereby providing additional support for the recognition of the eastern lineages as two distinct species. These lineages are described herein as Amolops gerutu sp. nov. from the eastern states of Kelantan, Terengganu, and Pahang, and A. australis sp. nov. from the southern-most state of Johor. In general, these two new species form a clade that is sister to A. larutensis and can be readily distinguished from it by having: (1) considerably denser and more pronounced dorsal tubercles, and (2) the posterodorsal surface of thighs having dense, dark stippling as opposed to broad vermiculations. Although differences in other morphometric characters were detected, their utility as diagnostic characters should be applied with caution due to the large intraspecific variation that overlaps among different species in many of the characters we measured. As such, we advocate for the use of tuberculation and pattern of the posterodorsal portion of the thighs as primary diagnostic characters. These characters can readily distinguish A. larutensis from the two new species. To differentiate A. australis sp. nov. from A. gerutu sp. nov. and A. larutensis, body size can be a good diagnostic character as A. australis sp. nov. is significantly smaller in both males (mean = 31.04 ± 1.59 mm) and females (mean = 46.48 ± 3.2 mm). Additionally, we show a strong positive correlation between body size and elevation, with populations from montane forests (>900 m asl) being considerably larger than populations at lower elevations.
  
Keywords: Amphibia, Taxonomy, systematics, morphology, amphibian, cryptic species, body size


Amolops gerutu sp. nov.
Tuberculated Torrent Frog

Amolops larutensis Sumarli, Grismer, Anuar, Muin & Quah, 2015, pp 4,9,12.

Distribution. Besides the type locality, Amolops gerutu sp. nov. has been documented from a number of other localities east of the Titiwangsa mountain range including Gunung Stong Forest Reserve, in the state of Kelantan; Lata Tembakah, Lata Belatan, and Sekayu Recreational Forest in the state of Terengganu (Dring 1979; Sumarli et al. 2015); and Sungai Lembing, Sungai Pandan Waterfall, and Chemerong Amenity Forest in the state of Pahang. At Gunung Stong, A. gerutu sp. nov. occurs in syntopy with A. larutensis (Fig. 1).

Natural history. Like most congeners, Amolops gerutu sp. nov. is a strict torrent specialist that only occurs within or along torrential zones of rocky streams from lowland to montane forests. During the day, frogs dwell in rock cracks and sheltered areas among boulder stacks along streams and are rarely seen out in the open. They can be seen in abundance at night, most frequently on boulders by splash zones and occasionally on adjacent low vegetation. When disturbed, frogs dive into the rapids and float downstream. Like other congeners, tadpoles of this species are gastromyzophorous (Pham et al. 2015) and can be seen clinging onto boulders in the splash zone. On such boulders, tadpoles are usually observed above or just below the water line.

Etymology. The specific epithet “gerutu” (English pronunciation “gir-roo-too”) refers to the Malay word of the same construct, meaning “tubercle”, in reference to the pronounced dorsal tubercles that are diagnostic of this species.


Amolops australis sp. nov.
Southern Torrent Frog

Amolops larutensis, Ahmad, Senawi & Lim 2004, p 26; Belabut & Hashim, 2005, p 200; Wood, Grismer, Youmans, Nasir, Ahmad & Senawi, 2008, p 118; Grismer & Pan, 2008, p. 277 (in part); Shahriza, Ibrahim, Anuar & Muin, 2012, p 558, 561.
Staurois larutensis, Belabut & Hashim, 2004, pp. 67, 69.

Distribution. Amolops australis sp. nov. is only known from the southern state of Johor where it has been confirmed to occur in Endau-Rompin National Park and Bantang River Amenity Forest. It is presumed to occur more widely in suitable habitats in the surrounding southern region of Peninsular Malaysia.

Natural history. The natural history of this species is similar to that of Amolops gerutu sp. nov. and A. larutensis. No information is available for tadpoles.

Etymology. The specific epithet is derived from the Latin word “ australis ”, meaning “southern” in English, and is applied in reference to the distribution of this species in southern Peninsular Malaysia that also represents the southern-most distributional limit of the entire genus.


Chan Kin Onn, Robin Kurian Abraham, Jesse L. Grismer and L. Lee Grismer. 2018. Elevational Size Variation and Two New Species of Torrent Frogs from Peninsular Malaysia (Anura: Ranidae: Amolops Cope). Zootaxa. 4434(2); 250–264. DOI:  10.11646/zootaxa.4434.2.2

Kin Onn Chan, Alana M. Alexander, Lee L. Grismer, et al. 2017. Species Delimitation with Gene Flow: A Methodological Comparison and Population Genomics Approach to Elucidate Cryptic Species Boundaries in Malaysian Torrent Frogs.  Molecular Ecology. DOI: 10.1111/mec.14296 

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