This genus is named for the Greek phryne, meaning toad, and batrachos, meaning frog. This refers to their toad-like appearance.
The common name, puddle frog, refers to the fact that many species breed in temporary waterbodies, including puddles, roadside ditches, and ﬂooded grassy depressions, although some also breed in permanent bodies of water, such as ponds, lakes, streams, and rivers (Rödel, 2000; Channing, 2001; Channing and Howell, 2006; IUCN et al., 2006).
Puddle frogs (genus Phrynobatrachus) are found in diverse terrestrial habitats across sub-Saharan Africa. Species are small in size (most less than 30 mm), most often brown in color, exhibit a tarsal tubercle and lack webbing between the fingers. Most species may exhibit chevron-shaped glands in the scapular region, but the size and shape of these glands are variable. There are currently 82 species described (Frost, 2011).
This genus is present across mainland sub-Saharan Africa and is also present on the islands of Zanzibar (Unguja) and Pemba on the East Coast, as well as Bioko, São Tomé, and Príncipe in the Gulf of Guinea (Rödel and Ernst, 2002a,b; Frost, 2011).
The size and shape of the chevron-shaped glands of Phrynobatrachus are variable; they can originate and terminate in the scapular region or extend almost the entire length of the body (Zimkus and Blackburn, 2008). Only in some species exhibit circummarginal grooves on the manual or pedal digit tips; in some species, these furrows are found only on the longest digits (Zimkus and Blackburn, 2008). Extent of pedal webbing is variable among Phrynobatrachus species; it ranges from (0) absent or rudimentary with 3.0–4.0 phalanges free on toe IV, to (1) moderate to extensive with 0–2.9 phalanges free on toe IV (Zimkus et al., 2012).
Males of some species possess a nuptial excrescence or thickened pad of skin on the medial and dorsal surface of the first finger. Breeding Phrynobatrachus males have a single subgular vocal sac, which, when not distended, may form one or multiple folds, roughly parallel to the lower jaw, on the lateral margins of the throat (Stewart, 1967; Zimkus and Blackburn, 2008).
Adult snout-vent lengths (SVL) vary greatly, from as little as 12 mm in some miniaturized species to greater than 50 mm in the largest species (Zimkus et al., 2012).
Puddle frogs can be distinguished by the presence of a tarsal tubercle, inner metatarsal tubercle and outer metatarsal tubercle. The dorsum is most often brown in color with or without a mid-dorsal strip. The skin may be warty or smooth, and most species may exhibit chevron-shaped glands in the scapular region, but the size and shape of these glands are variable. Fingers lack webbing; pedal webbing ranges from absent to extensive. Pupils are horizontal.
Squeaker frogs of the genus Arthroleptis and puddle frogs of the genus Phrynobatrachus are distantly related but have been confused for more than a century and continue to be difficult for many to distinguish. Definitive characteristic that can be used to differentiate between them include the presence of an outer metatarsal tubercle and a tarsal tubercle in Phrynobatrachus. Arthroleptis only exhibits an inner metatarsal tubercle, which is also found in Phrynobatrachus. Arthroleptis generally have relatively wider heads than Phrynobatrachus (Zimkus and Blackburn, 2008).
Habitat and Ecology
Puddle frogs occupy a diverse range of habitats, including primary and secondary forests,savannas, grasslands, and agricultural areas (Zimkus et al., 2010). They are also distributed across a wide altitudinal range from lowland areas to montane regions up to approximately 3000 m (IUCN et al., 2006).
Life History and Behavior
Most puddle frogs deposit hundreds to thousands of eggs in ponds, streams, or pools, but a small number of species deposit small clutches of eggs in stagnant water found in tree holes, in empty fruit capsules, within snail shells, or terrestrially (Rödel, 1998; Rödel and Ernst, 2002; Zimkus et al., 2012). Species exhibiting these alternative reproductive modes include P. dendrobates, P. guineensis, P. krefftii, P. phyllophilus, P. sandersoni, and P. tokba, although all have free-living tadpoles (Amiet, 1981; Rödel, 1998; Rödel and Ernst, 2002).
Zimkus et al. (2012) found that most Phrynobatrachus species breed in small bodies of water and have aquatic eggs with free-living, feeding tadpoles. However, reproductive modes that provide autonomy from permanent water bodies evolved independently at least seven times.
Evolution and Systematics
Zimkus et al. (2012) found that most Phrynobatrachus species breed in small, lotic bodies of water and have aquatic eggs with free-living, feeding tadpoles. However, reproductive modes that provide autonomy from permanent water bodies evolved independently at least seven times. These shifts towards alternate reproductive modes are not linked to a common temporal event, clades that exhibit alternate reproductive modes have lower diversification rates than those that deposit eggs aquatically. In addition, adult habitat, pedal webbing and body size have no effect on diversification rates. Although these traits are not associated with increased speciation rates, they may still provide opportunities to extend into new niches, thus increasing overall diversity.
Molecular Biology and Genetics
Relationships among puddle frogs of the family Phrynobatrachidae (one genus: Phrynobatrachus) were reconstructed using mitochodrial sequence data from 12S rRNA, valine-tRNA, and 16S rRNA fragment, as well as combined sequence data from mitochondrial and nuclear (RAG-1) genes (Zimkus et al., 2010). Monophyly of the Phrynobatrachidae is well supported, and three major clades of Phrynobatrachus are identiﬁed. Biogeographic history was also reconstructed using habitat preference, geography and elevation data Most species favor forest over savanna habitats, and the most recent common ancestor of the Phrynobatrachidae reconstructed as a forest species. Three independent colonizations of highland regions were identified, one in each of the three major clades. Ancestral reconstructions support an East African origination of puddle frogs. Most species are restricted to one of ﬁve sub-Saharan regions and are distributed within the Eastern, Central, and Western zones with far fewer species in Southern Africa.
Statistics of barcoding coverage
|Specimen Records:||40||Public Records:||1|
|Specimens with Sequences:||23||Public Species:||0|
|Specimens with Barcodes:||23||Public BINs:||1|
|Species With Barcodes:||3|
IUCN Red List Category and Justification of Conservation Status
The IUCN (2012) lists 25% of all Phrynobatrachus species as Near Threatened, Vulnerable, Endangered or Critically Endangered. The majority are considered of Least Concern (42%), while a large number are considered Data Deficient (34%).
The dwarf puddle frogs or African puddle frogs make up the genus Phrynobatrachus with over 70 species. These Afrotropical true frogs are placed in the subfamily Petropedetinae, which some authors consider a distinct family. This is occasionally split up further, particularly in older sources, with the present genus being placed in a family Phrynobatrachidae.
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