Description
Hyla suweonensis has a snout-to-vent length of 27.1 - 31.7 mm. Its pupils are round, and the head is narrower than the body, which is long and slender. The skin is rough on the underside and smooth on the back. No skin folds are present and the limbs are long and slender. The toes are rounded with circummarginal disks at their tips. Webbing is absent between the fingers and only vestigial between the toes. No nuptial pads are visible. Hyla suweonensis is scansorial, meaning it is adapted for climbing (Borzée et al. 2013, Kuramoto 1980).

It is easily confused with H. japonica, a sympatric and morphologically similar species. There are a few distinguishing characteristics that provide for reliable field identification between both species, though they are mostly useful for sympatric populations. Hyla suweonensis is smaller and more slender, and is much less likely to show black bars on its forearms, though this is not a useful diagnostic characteristic as it is present in both species. The angle between the two lines connecting the posterior corner of the eyes and the ipsilateral nostrils is the most accurate morphological criteria for species identification, ranging from 66.9° - 72.8° in H. suweonensis and from 76.5° – 85.0° in H. japonica. The vocal sac is yellow in H. suweonensis versus dark-colored in H. japonica, though no comparative studies have been conducted. Hyla suweonensis calls during the day and night, while H. japonica only calls at night. Hyla suweonensis usually calls from the centre of rice paddies while holding onto rice seedlings with its body propped out of the water, whereas H. japonica usually calls while sitting on the ground or in shallow water at the edge of rice paddies. The call duration is longer in H. suweonensis than in H. japonica (Borzée et al. 2013, Jang et al. 2011, Jang and Borzée 2014, Kim et al. 2012, Kuramoto 1980, Park et al. 2013).

In life, it has a green back during the breeding season, and may be dark grey or brown the rest of year. Dark patches may or may not be present at this time. The underside is white, with possible yellow lining below the black lateral line. Males have a yellow vocal sac during the breeding season, but it can be dark green in rare cases. The forearms may have black bars, though this is very infrequent. No information is available on its coloration in preservative (Borzée et al. 2013, Kuramoto 1980).

Much of the variation within the species is found in its coloration as described above.

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Korea, Republic of

	View distribution map in BerkeleyMapper.
	View Bd and Bsal data (38 records).

Hyla suweonensis occurs on the northwest plain of the Republic of Korea, from the city of Munsan to the city of Iksan. A single population is known to occur in the vicinity of the city of Pyeongyang in the Democratic People’s Republic of Korea. All populations in the Republic of Korea are below 100 m asl. The typical habitat of the species is rice paddies, but it has been found in a single semi-natural wetland site rich in foxtail grass (Alopecurus aequalis) and high reeds (Typha spp.). The wetland site is mostly surrounded by Korean willows (Salix koreensis) and occasional high grasses (Elymus repens and Phragmites communis; Borzée and Jang 2015, Chun et al. 2012, Jang et al. 2011, Roh et al. 2014).

Life History, Abundance, Activity, and Special Behaviors
Males produce advertisement calls from the late afternoon to a few hours after sunset, but feed only during the daytime. When not calling, it is generally found on vegetation by the edge of rice paddies. It is fossorial during its hibernation period. This species is exclusively associated with shallow wetlands in the form of rice paddies. These rice paddies are temporary, standing and with low circulation. The breeding season is related to rice paddy cultivation and occurs between late April and early July. Males usually produce calls while hanging onto vegetation with all four limbs (Borzée and Jang 2015, Jang and Borzée 2014).

The notes of the male advertisement call consist of several single pulses, followed by a connected pulse. The mean call bout is 5.84 ± 2.31 s and the mean interval between bouts is 9.46 ± 5.50 s (Jang et al. 2011, Park et al. 2013).

Trends and Threats
The species is rare and has been listed as critically endangered by the Ministry of Environment of the Republic of Korea in 2012 and as endangered by the IUCN (Borzée and Matsui 2014, Ministry of Environment of Environment ROK 2012).

The species is declining in population and geographic range, primarily due to habitat loss. Rice paddies are adequate surrogate breeding habitats but are regularly claimed for other purposes. Species decline is further linked to habitat fragmentation, urbanization and small population sizes (Borzée and Matsui 2014).

Competition with the much more abundant H. japonica may also contribute to its population decline, as H. japonica species is known to carry the chytrid fungus (Batrachochytrium dendrobatidis). Protected wetlands are present on the geographic range of H. suweonensis but the species does not occur in any of them (Borzée and Jang 2015, Roh et al. 2014).

Relation to Humans
The species occurs primarily in man made rice paddies (Borzée and Jang 2015).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Intensified agriculture or grazing
Urbanization
Drainage of habitat
Habitat fragmentation
Local pesticides, fertilizers, and pollutants
Long-distance pesticides, toxins, and pollutants
Introduced competitors
Disease
Loss of genetic diversity from small population phenomena
Loss of distinctiveness through hybridization

Comments
The species authority is: Kuramoto, M. (1980). "Mating Calls of Treefrogs (Genus Hyla) in the Far East, with Description of a New Species from Korea." Copeia, 1980(1), 100-108.

Genotypic data point to a ZW sex determination system in H. suweonensis, as previously proposed based on cytogenetic analyses (Dufresnes et al. 2015, Yu and Lee 1988).

The species epithet suweonensis is derived from where the species was first discovered, in the city of Suweon (also spelled “Suwon”) in South Korea (Kuramoto 1980).

References

Borzée, A., Jang, Y. (2015). ''Description of a seminatural habitat of the endangered Suweon treefrog, Hyla suweonensis.'' Animal Cells and Systems, 10.1080/19, 1-5.

Borzée, A., Park, S., Kim, A. Kim, H. T., Jang, Y. (2013). ''Morphometrics of two sympatric species of tree frogs in Korea: a morphological key for the critically endangered Hyla suweonensis in relation to H. japonica.'' Animal Cells and Systems, 17(348-356).

Chun, S., Chung, E., Voloshina, I., Chong, J. R., Lee, H., Min, M. S. (2012). ''Genetic Diversity of Korean Tree Frog (Hyla suweonensis and Hyla japonica): Assessed by Mitochondrial Cytochrome b Gene and Cytochrome Oxidase Subunit I Gene.'' Korean Journal of Herpetology, 4, 31-41.

Dufresnes, C., Borzée, A., Horn, A., Stöck, M., Ostini, M., Sermier, R., Wassef, J., Litvinchuk, S., Kosch, T. A., Waldman, B., Jang, Y., Brelsford, A., Perrin, N. (2015). ''Sex-chromosome homomorphy in Palearctic tree frogs proceeds from both turnovers and X-Y recombination.'' Molecular Biology and Evolution, 10.1093/molbev/msv113, 1-10.

Jang, Y., Borzée, A. (2014). ''Research on Microhabitat Differentiation Between Two Treefrog Species May Reveal the Cause of Population Decline in the Endangered Hyla suweonensis in Korea.'' FrogLog, 22, 48-50.

Jang, Y., Hahm, E. H., Lee, H. J., Park, S., Won, Y. J., Choe, J. C. (2011). (2011). ''Geographic variation in advertisement calls in a tree frog species: gene flow and selection hypotheses.'' PLoS One, 6(e23297).

Kim, I. H., Son, S. H., Kang, S. W., Kim, J. B. (2012). ''Distribution and Habitat Characteristics of the Endangered Suweon-Tree Frog (Hyla suweonensis).'' Korean Journal of Herpetology, 4, 15-22.

Kuramoto, M. (1980). ''Mating Calls of Treefrogs (Genus Hyla) in the Far East, with Description of a New Species from Korea.'' Copeia, 1980(1), 100-108.

Ministry of Environment ROK. (2012). Hyla suweonensis. http://www.me.go.kr/web/4245/ysg/common/board. Accessed on 30 January 2013.

Park, S., Jeong, G., Jang, Y. (2013). ''No reproductive character displacement in male advertisement signals of Hyla japonica in relation to the sympatric H. suweonensis.'' Behavioral Ecology and Sociobiology, 67, 1345-1355.

Roh, G., Borzée, A., Jang, Y. (2014). ''Spatiotemporal distributions and habitat characteristics of the endangered treefrog, Hyla suweonensis, in relation to sympatric H. japonica.'' Ecological Informatics, 24, 78-84.

Yu, S., Lee, H. (1988). ''Comparative karyological analysis of the Korean tree frogs, Hyla japonica and Hyla suweonensis (Anura, Hylidae).'' Korean Journal of Zoology, 33, 1-5.

Species Account Citation: AmphibiaWeb 2023 Hyla suweonensis: Suweon treefrog <https://amphibiaweb.org/species/971> University of California, Berkeley, CA, USA. Accessed Nov 21, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 21 Nov 2024.

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