Fejervarya, Bolkay, 1915

Kaiser, Hinrich, Carvalho, Venancio Lopes, Ceballos, Jester, Freed, Paul, Heacox, Scott, Lester, Barbara, Richards, Stephen J., Trainor, Colin R., Sanchez, Caitlin & O'Shea, Mark, 2011, The herpetofauna of Timor-Leste: a first report, ZooKeys 109, pp. 19-86 : 28-29

Genus Fejervarya Fig. 4

Common names.

(E) Rice Paddy Frogs. (T) Manduku natar (manduku = frog, natar = rice paddy).

Identification.

Rice paddy frogs ( Fig. 4 ) are the most common amphibians found in regions with rice agriculture. They may grow to over 60 mm in snout-vent length and can usually be recognized by their fairly stout body shape, brownish to gray-green coloration, shiny moist skin with ill-defined dorsal and lateral patterns, and warts scattered irregularly or in rows along the back (e.g., Fig. 4B ).

Collection and natural history.

As the name suggests, rice paddy frogs are commonly found in rice paddies where they perch at the water’s edge, on tufts of vegetation, or even on cow patties. Our survey documented at least three species of rice paddy frogs in Timor-Leste, with two or more often occurring in the same suitable habitat. Species can be distinguished by the size of mature males, which can be clearly separated into three groups by their size, morphology of the tympanum and its associated structures, and the patterning of the throat in males. One of the species, designated as Fejervarya sp. 1 [Ca CMD 431] is a lowland form and most similar to Fejervarya verruculosa ( Roux 1910). This candidate species differs from Fejervarya verruculosa by the shape of the supratympanic fold, the size of the tympanum relative to the eye, patterning on the hidden surfaces of the legs, and number and position of maxillary teeth and the shape of the alary process of the premaxilla, among other characters. The other two candidate species can also be differentiated by these and other characters, and they have been designated Fejervarya sp. 2 [Ca CMD 508] and Fejervarya sp. 3 [Ca CMD 355].

Among the specific habitats where we encountered these frogs were active rice paddies, roadside puddles, coffee plantations, and coastal forests at altitudes between 4 m and 1187 m. Our observations are consistent with those of Menzies (1987) but we believe that not all three presumptive species are capable of such habitat plasticity. More detailed investigation is needed to clarify the habitat requirements of these three candidate Fejervarya species.

Biogeography.

The presence in Timor-Leste of three morphologically similar and seemingly endemic dicroglossid frogs, with an evolutionary origin in Asia, raises interesting biogeographic questions. The simplest explanation would be a single or a series of introductions in modern times, with the influx of peoples and cargo from points all across the Indonesian Archipelago. However, a more ancient, classic island biogeography scenario is also feasible. Based on the two main concepts of speciation, sympatric speciation among amphibians is possible but presumed rare among dicroglossid frogs. The concept of allopatric speciation is the alternative, by which the three species may represent descendants of three separate introductions that occurred as early farmers brought rice plants to the island. It is generally accepted that rice agriculture originally spread from China into South and Southeast Asia ( Crawford and Chen 1998) and reached the Lesser Sunda Islands in waves after spreading throughout the Greater Sunda Islands during the Neolithic Period ( Chi and Hung 2008). During this time, it is quite possible that stowaway frogs arrived on Timor with rice plants. The occurrence of several similar rice paddy frog species in sympatry is not unique to Timor-Leste (e.g., Burma; G. Zug, in litt.). Molecular studies to obtain some insights into this conundrum are progressing. The hypothesis that multiple human-mitigated introductions of Fejervarya populations occurred mirroring the development of rice cultivation is a plausible explanation for the many species of this genus listed as incertae sedis with respect to their intrageneric relationships.

Figures

Figure 4. Rice paddy frogs, genus Fejervarya. A Fejervarya sp. 1 from the Baucau area (SVL 58 mm) B Fejervarya sp. 2 from the Viqueque area (SVL 46 mm) C Fejervarya sp. 3 from the Viqueque area (SVL 38 mm) D All three species of rice paddy frogs found in Timor-Leste may show varying degrees of green coloration on the dorsal and lateral parts of the body. This specimen (SVL 56 mm) from the Viqueque area represents the most extreme green coloration we observed, in terms of both brightness and coverage. Photos by Mark O'Shea.