Target-enriched DNA sequencing from historical type material enables a partial revision of the Madagascar giant stream frogs (genus Mantidactylus)

ABSTRACT

The subgenus Mantidactylus is a group of frogs endemic to Madagascar, including the largest anuran species on the island. Although these frogs are common and widely distributed, their taxonomy remains unclear. Two species are currently recognised, M. grandidieri and M. guttulatus, with another available name, Rana pigra, considered to be a synonym of M. grandidieri. However, molecular studies have suggested the presence of several cryptic species within the group. Additionally, due to the lack of prominent morphological features, allocating the available names to evolutionary lineages has proven challenging. In the present study, we take a first step towards solving these problems by using fragments of the 16S mitochondrial gene and RAG1 nuclear gene from all over the range of the subgenus to describe its genetic diversity. We also use a newly designed target enrichment laboratory protocol to sequence three mitochondrial fragments from five name-holding museum specimens (as old as 120 years) in order to determine to which lineages the existing names should be applied. The study of the 16S mitochondrial gene revealed 7 geographically separated lineages, distinct enough to be considered candidate species. Out of the five museum specimens analysed, four successfully yielded DNA sequences and could be attributed to one of the aforementioned lineages. Therefore, the name Mantidactylus grandidieri should be applied to the populations from North-Eastern Madagascar, while M. guttulatus refers to populations from inland localities along the Eastern coast of the island. On the other hand, the holotype of Rana pigra did not yield enough genetic material to allow definitive identification. While our data were not sufficient to assess the status of the four lineages distributed along the Eastern coast, the populations from North-Western Madagascar were highly distinct on both the mitochondrial and nuclear markers. We thus describe them as a new species, M. radaka sp. nov.

http://www.zoobank.org/urn:lsid:zoobank.org:pub:1EDDAF0D-FE37-490A-B09E-E136A0C5CB35     

A new species of Mantidactylus (subgenus Guibemantis) from Madagascar,with a comparative survey of internal femoral gland structure in the genus (Amphibia: Ranidae: Mantellinae)

A new species of Mantidactylus (subgenus Guibemantis) from the rainforests of eastern Madagascar is described. The new species is sympatric with the closely related M. depressiceps (Boulenger, 1882) and M. tornieri (Ahl, 1929) but differs by larger size, a more strongly developed prepollex, and by advertisement calls. Mantidactylus acuticeps Ahl, 1929 and Rhacophorus mocquardii Boulenger, 1896 are confirmed to be junior synonyms of M. depressiceps. The presence of distinct femoral glands in the new species was noted; a feature so far not reliably recognized in other members of the subgenus Guibemantis. Femoral gland structure was investigated in representatives of each of the subgenera included in Mantidactylus by dissecting and reflecting the femoral skin. Four femoral gland types were identified. Type 1: many small, single granules in an ill-delimited patch, grouped in rosettes at the patch edges; type 2: a group of moderately sized granules in a well-delimited patch; type 3: comprising two different structures: distal granules enclosing externally a distinct central depression, and smaller proximal granules or groups of granules; type 4: as type 3, but lacking the proximal granules. Mantidactylus rivicola Vences, Glaw and Andreone, 1997, M. cf. malagasius (Methuen and Hewitt, 1913) and M. ventrimaculatus (Angel, 1935) differed from all other species examined; their femoral glands comprise a reduced number of large granules with an indistinct central depression in external view. The presence of a distal granule group with external central depression (types 3 and 4 above) provides a probable synapomorphy for the subgenera Brygoomantis, Ochthomantis, Hylobatrachus, Chonomantis and Mantidactylus. In females of these subgenera rudimentary femoral glands are present, but they lack completely in females of the other groups.