Description
Dryophytes flaviventris is also known as the Yellow-bellied tree frog and is a small scansorial tree frog, very morphologically similar to D. suweonensis. The snout-vent length of the species is about 28.59 mm. Its head width is slightly smaller than the length, and the average eye length is 3.47 mm. The eyes have horizontal pupils. Their skin texture is interesting: while it is shagreened ventrally, it is smooth dorsally. Also, they have no skin folds on their body and no webbing on the fingers. The limbs are long and slender. They do not have vestigial webbing between toes and the toes end with circummarginal discs. No nuptial pads are visible (Borzée et al. 2020).

Dryophytes flaviventris was firstly reported in 2016 as D. suweonensis in an extended range of distribution. However, they were later determined to be different species with D. flaviventris being morphologically and vocally similar to D. suweonensis, and together are closely related and similar to D. immaculatus. More specifically, D. flaviventris differs from D. suweonensis by the former having a slightly more elongated body and limbs. Dryophytes flaviventris can also be differentiated from D. immaculatus and D. suweonensis by having an intermediate length of webbing between the 2nd and 3rd toes. Unlike D. suweonensis, which in some very uncommon cases have green colored throats in males, all D. flaviventris have yellow throats during the breeding season. Although these three clades exhibit similar behavior during advertisement calls, a difference observed is that D. flaviventris have longer note lengths and more frequent independent pulses before the connected pulse. Also, when producing the advertisement call, males use their forelimb to hold the vegetation, which is an essential characteristic that can be used to distinguish the D. immaculatus group and D. japonicus group (Borzée and Yu et al. 2016, Borzée et al. 2020).

This species is white with a yellow hue on its immaculate ventrum. Occasionally, there is a yellow lining below the black lateral line, which eventually fades out at the belly. Males have yellow throats and light green dorsum during the breeding season. However, when it is not breeding season, they can have dark gray or brown dorsums. It’s unclear if this description is in life or preservative (Borzée et al. 2020).

When D. flaviventris is not in breeding season, some individuals have brown and dark gray dorsal coloration. The males and females differ in that the females have yellow hues and males and yellow markings (Borzée et al. 2020).

Distribution and Habitat

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

View distribution map in BerkeleyMapper.

Dryophytes flaviventris is found on and around the Chilgap Mountain of South Korea, where the temperature reaches -7˚C during the coldest seasons. They are also found in Buyeo county, Nonsan city, and Iksan city of South Korea. The populations inhabiting Gunsan and Wanju were disturbed and completely eradicated by invasive populations of American Bullfrogs and land conversion. Although the habitat range of D. suweonensis and D. flaviventris are close, they barely overlap. The natural wetland habitats of D. flaviventris is unknown, and all populations can be only found in rice paddies at low elevations (Borzée et al. 2020).

Life History, Abundance, Activity, and Special Behaviors

Dryophytes flaviventris hibernates around the area of rice paddies and is scansorial, meaning that they are able to climb. Furthermore, inguinal loops were not found in Dryophytes flaviventris (Borzée et al. 2020).

The breeding season overlaps with rice paddy cultivation from late April to early July – the males’ advertisement calls start mid-day, and they use their forelimbs to cling to the edge of rice paddies. Dryophytes flaviventris generally have long note lengths and exhibit more independent pulses before letting out a connected one. The duration of connected pulses were recorded as 0.094s at 21.69˚C. The average frequency of pulses and notes were 2172.72 Hz and 2195.16 Hz, respectively. The peak dominant frequency of pulses and notes were 3207.28 Hz and 2199.86 Hz, respectively. They had about 6.64 independent pulses with note duration being 0.15s (Borzée et al. 2020).

Among the other Dryophytes species that inhabit the Korean Peninsula, D. flaviventris occurs at the lowest elevation (0 - 30 m). This distribution may imply the species is tolerant to brackish water in contrast to other local tree-frog species. The low elevations in which D. flaviventris can be encountered, in fact, are relatively close to the coast and can experience fluvial processes, which may create an obstacle to the cutaneous respiration on which this particular genus relies (Andersen et al. 2022).

Larva
The larval form of D. flaviventris is quite similar to the tadpoles of D. suweonensis; they can grow up to 3 cm, have pointy tails, dorsolateral eyes, dorsal nostrils, and transparent fins (Borzée et al. 2020).

While they are generally brown and have patches, some individuals have a reddish-colored ventral side and darker patches (Borzée et al. 2020).

Trends and Threats
Dryophytes flaviventris was abundant decades ago, but both the population and range of distribution are now decreasing (Borzee et al. 2020). While the population dynamics of D. flaviventris is better than that of D. suweonensis, its populations are decreasing due to constricted ranges and habitat loss. Additionally, the populations inhabiting Gunsan-si and Wanju-gun, a city and county in North Jeolla Province, respectively, were disturbed and completely eradicated by invasive populations of American Bullfrogs and land conversion (Borzée et al. 2020).

As of 2022, there is no protected area for D. flaviventris, but Borzée and Kim et al. (2017) state that it is urgent and necessary to design a protected area for the species and many other frog species in the Republic of Korea. Additionally, the policies that applied to protect D. suweonensis can also be utilized to protect D. flaviventris (Borzée and Kim et al. 2017, Borzée et al. 2020).

For D. flaviventris and many frogs, agricultural wetlands, such as rice paddies, are generally suitable habitats with regular hydro cycles. It is very necessary to distinguish and implement the traditional agricultural wetlands instead of the industrialized ones. This is because industrialized rice paddies have cemented banks and underground hydration pathways, which is not adequate to support the survival and breeding of the amphibians (Borzée et al. 2020).

The ecological role of the species in its environment is poorly understood as little is known about its diet, interactions with conspecifics, or interspecific interactions/competition. However, there is evidence that the species is vulnerable to introduced anuran species, such as Rana catesbeiana (American bullfrog); populations of D. flaviventris that used to occur across the cities of Gunsan and Wanju (South Korea) were extirpated soon after the arrival and spread of American bullfrogs (Borzée et al. 2020). Furthermore, R. catesbeiana has been recognized as a vector for a pathogenic chytrid fungus (Batrachochytrium dendrobatidi) that causes a skin disease and can result in death in many frog species (Borzée and Kosch et al. 2017). Further research needs to be conducted on the risks to D. flaviventris.

Relation to Humans
Dryophytes flaviventris is strongly associated with rice paddies like D. suweonensis (Borzee and Jang 2015, Borzee et al. 2020).

Possible reasons for amphibian decline

General habitat alteration and loss
Intensified agriculture or grazing
Habitat fragmentation
Local pesticides, fertilizers, and pollutants
Introduced competitors

Comments
Dryophytes flaviventris was first documented in 2016 as a subspecies of D. suweonensis (Borzée and Yu et al. 2016).

Based on Bayesian methods on genetic ddRADseq loci, D. suweonensis is sister to D. flaviventris, and together they are sister to D. immaculatus (Borzée et al. 2020).

The species epithet, "flaviventris", comes from the combination of Latin words “flavus”, which means “yellow”, and “ventris”, which means “belly” and refers to the yellow marking on males and yellow hues on females (Borzée et al. 2020).

The range in which D. flaviventris occurs is proximal to another tree frog of the Korean Peninsula, D. suweonensis, commonly known as Suweon treefrog. Prior to genetic testing, the two species were believed to be a single species. However, despite their distribution ranges being geographically close, the Chilgap mountain range separates the species to the extent that no overlap of their distribution or interspecific interactions are recorded (Borzée et al. 2020).

References

Andersen, D., Chuang, M. F., Choe, M., Kim, A., Kwon, S., Jang, Y., Borzée, A. (2022). Elevational distribution of amphibians: resolving distributions, patterns, and species communities in the Republic of Korea. Zoological Studies, 61:25 [a target="_blank" href="https://zoolstud.sinica.edu.tw/Journals/61/61-25.pdf">link

Borzee A., Jang Y. (2015). Description of a seminatural habitat of the endangered Suweon treefrog, Hyla suweonensis. Animal Cells and Systems, 19(3): 1 – 5. [link]

Borzee, A., Kim, K., Heo, K., Jablonski, P. G., Jang, Y. (2017). Impact of land reclamation and agricultural water regime on the distribution and conservation status of the endangered Dryophytes suweonensis. PeerJ, 5: e3872. [link]

Borzee, A., Kim, J. Y., Jang, Y. (2016). Asymmetric competition over calling sites in two closely related treefrog species. Scientific Reports, 6. [link]

Borzee, A., Kosch, T. A., Kim, M., Jang, Y. (2017). Introduced bullfrogs are associated with increased Batrachochytrium dendrobatidis prevalence and reduced occurrence of Korean treefrogs. PLoS ONE, 12(5): e0177860. [link]

Borzée, A., Messenger, K. R., Chae, S., Andersen, D., Groffen, J., Kim, Y. I., An, J., Othman, S. N., Ri, K., Nam, T. Y., Bae, Y., Ren, J.-L., Li, J.-T., Chuang, M.-F., Yi, Y., Shin, Y., Kwon, T., Jang, Y., Min, M.-S. (2020). Yellow sea mediated segregation between North East Asian Dryophytes species. PLoS ONE 15(6): e0234299. [link]

Borzee, A., Yu, S. H., Jang, W. (2016). Dryophytes suweonensis (Suweon Treefrog). Herpetological Review, 47(3): 418. [link]

Species Account Citation: AmphibiaWeb 2023 Dryophytes flaviventris: English: Yellow-bellied treefrog; Korean: 노랑배청개구리; Chinese: 黄腹雨蛙 <https://amphibiaweb.org/species/9224> University of California, Berkeley, CA, USA. Accessed Apr 18, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 18 Apr 2024.

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