Table 1.

Definitions of proposed categories of candidate species

CategoryGeneral definitionDefinition used in Malagasy frogs
Unconfirmed Candidate Species (UCS)Default category for deep genealogical lineages of unknown status. The genetic differentiation must be above a threshold value typical for comparisons among closely related species in the group of animals under study. Data deficient for morphology, ecology, and distribution.Uncorrected pairwise genetic divergences in 16S rRNA gene >3% to all other described species. No data on morphology and bioacoustics due to unavailability of voucher specimens or immature state of vouchers.
Confirmed Candidate Species (CCS)Specimens or populations characterized by a detectable genetic differentiation to all described species, not necessarily above any threshold, but in concordance with at least one of the following criteria:

  1. a distinct differentiation in a character that mediates a premating reproductive barrier,

  2. a diagnostic morphological difference in a character that in the respective group of animals is known to be of low intraspecific variability and of high value to discriminate species,

  3. sympatric occurrence without admixture, and with at least one phenotypic character state difference, even if subtle, strictly correlated to the genealogy inferred from a neutral molecular marker.

Uncorrected pairwise genetic divergences in 16S rRNA gene to all other described species in most cases >3%, sometimes only 1–2%. Concordance of this molecular differentiation with one of the following:

  1. a qualitative difference in advertisement calls,

  2. diagnostic difference in at least one morphological character known to be generally species-specific in Malagasy frogs: e.g., presence and extent of dermal spines, ridges and tubercles, extension of terminal finger tips, morphology of femoral glands, relative tympanum size, iris color, or tadpole mouthparts.

Deep Conspecific Lineage (DCL)Deep genealogical lineages above a threshold value typical for comparisons among closely related species in the group of animals under study. One or several of the following must apply:

  1. morphological and chromatic data reveal no differences to topotypic populations of a described species, or only subtle differences in characters that are known to show intraspecific variability, or only quantitative differences (in characters such as body size),

  2. if characters relevant for premating isolation are known, then these show no or only quantitative differences to topotypic populations of described species,

  3. phylogeographic studies are available and show indications for genetic admixture with other genealogical lineages within a species.

Uncorrected pairwise genetic divergences in 16S rRNA gene > 3% to all other described species in combination with one or several of the following:

  1. no morphological differences, or differences only in characters known to show intraspecific variability: e.g., size, relative hindlimb length, body color and pattern,

  2. no difference in advertisement calls, or only differences in variables known to show intraspecific variability,

  3. co-occurrence with other deeply divergent haplotypes within the same populations, not concordant with any distinct or subtle morphological difference among individuals.