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      A new frog species of the subgenus Asperomantis (Anura, Mantellidae, Gephyromantis) from the Bealanana District of northern Madagascar

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          Abstract

          A recent study on a group of rough-skinned Gephyromantis frogs from Madagascar (Anura: Mantellidae: Mantellinae) established a new subgenus, Asperomantis, with five described species and one undescribed candidate species. Based on newly collected material from the Bealanana District, we address the taxonomy of this candidate species, and reveal that it consists of two populations with low genetic and morphological divergence but considerable bioacoustic differences that are obvious to the human ear. As a result, we describe some of the specimens formerly assigned to Gephyromantis sp. Ca28 as G. angano sp. n. and assign the remaining specimens from a locality between Bealanana and Antsohihy to a new Unconfirmed Candidate Species, G. sp. Ca29. Gephyromantis angano sp. n. is a small species that strongly resembles G. asper and G. ceratophrys, but it differs from these and all other Gephyromantis species by a unique, clinking advertisement call. The new species may be highly threatened by habitat fragmentation, but at present we recommend it be treated as Data Deficient until more data are available to assess its distribution. We discuss the curious relationship between G. angano sp. n. and G. sp. Ca29, which we suspect may represent a case of incipient speciation. We also identify two additional new Unconfirmed Candidate Species of Gephyromantis based on sequence data from other specimens collected during our surveys in the Bealanana District.

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          Most cited references 14

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          Vast underestimation of Madagascar's biodiversity evidenced by an integrative amphibian inventory.

          Amphibians are in decline worldwide. However, their patterns of diversity, especially in the tropics, are not well understood, mainly because of incomplete information on taxonomy and distribution. We assess morphological, bioacoustic, and genetic variation of Madagascar's amphibians, one of the first near-complete taxon samplings from a biodiversity hotspot. Based on DNA sequences of 2,850 specimens sampled from over 170 localities, our analyses reveal an extreme proportion of amphibian diversity, projecting an almost 2-fold increase in species numbers from the currently described 244 species to a minimum of 373 and up to 465. This diversity is widespread geographically and across most major phylogenetic lineages except in a few previously well-studied genera, and is not restricted to morphologically cryptic clades. We classify the genealogical lineages in confirmed and unconfirmed candidate species or deeply divergent conspecific lineages based on concordance of genetic divergences with other characters. This integrative approach may be widely applicable to improve estimates of organismal diversity. Our results suggest that in Madagascar the spatial pattern of amphibian richness and endemism must be revisited, and current habitat destruction may be affecting more species than previously thought, in amphibians as well as in other animal groups. This case study suggests that worldwide tropical amphibian diversity is probably underestimated at an unprecedented level and stresses the need for integrated taxonomic surveys as a basis for prioritizing conservation efforts within biodiversity hotspots.
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            Deciphering amphibian diversity through DNA barcoding: chances and challenges.

            Amphibians globally are in decline, yet there is still a tremendous amount of unrecognized diversity, calling for an acceleration of taxonomic exploration. This process will be greatly facilitated by a DNA barcoding system; however, the mitochondrial population structure of many amphibian species presents numerous challenges to such a standardized, single locus, approach. Here we analyse intra- and interspecific patterns of mitochondrial variation in two distantly related groups of amphibians, mantellid frogs and salamanders, to determine the promise of DNA barcoding with cytochrome oxidase subunit I (cox1) sequences in this taxon. High intraspecific cox1 divergences of 7-14% were observed (18% in one case) within the whole set of amphibian sequences analysed. These high values are not caused by particularly high substitution rates of this gene but by generally deep mitochondrial divergences within and among amphibian species. Despite these high divergences, cox1 sequences were able to correctly identify species including disparate geographic variants. The main problems with cox1 barcoding of amphibians are (i) the high variability of priming sites that hinder the application of universal primers to all species and (ii) the observed distinct overlap of intraspecific and interspecific divergence values, which implies difficulties in the definition of threshold values to identify candidate species. Common discordances between geographical signatures of mitochondrial and nuclear markers in amphibians indicate that a single-locus approach can be problematic when high accuracy of DNA barcoding is required. We suggest that a number of mitochondrial and nuclear genes may be used as DNA barcoding markers to complement cox1.
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              Reinforcement drives rapid allopatric speciation.

              Allopatric speciation results from geographic isolation between populations. In the absence of gene flow, reproductive isolation arises gradually and incidentally as a result of mutation, genetic drift and the indirect effects of natural selection driving local adaptation. In contrast, speciation by reinforcement is driven directly by natural selection against maladaptive hybridization. This gives individuals that choose the traits of their own lineage greater fitness, potentially leading to rapid speciation between the lineages. Reinforcing natural selection on a population of one of the lineages in a mosaic contact zone could also result in divergence of the population from the allopatric range of its own lineage outside the zone. Here we test this with molecular data, experimental crosses, field measurements and mate choice experiments in a mosaic contact zone between two lineages of a rainforest frog. We show that reinforcing natural selection has resulted in significant premating isolation of a population in the contact zone not only from the other lineage but also, incidentally, from the closely related main range of its own lineage. Thus we show the potential for reinforcement to drive rapid allopatric speciation.
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                Author and article information

                Journal
                Zoosystematics and Evolution
                ZSE
                Pensoft Publishers
                1860-0743
                1435-1935
                November 15 2017
                November 15 2017
                : 93
                : 2
                : 451-466
                Article
                10.3897/zse.93.14906
                © 2017

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