Genetic variation of an endangered Malagasy frog, Mantella cowani, and its phylogeographic relationship to the widespread M. baroni

Abstract

We investigated the degree and distribution of the genetic variation, and phylogeography, of two species of Malagasy poison frogs, Mantella cowani and M. baroni. The former is critically endangered due to its restricted distribution, habitat destruction and overcollection for the pet trade. Analysis of 526 bp of mtDNA (cytochrome b) resulted in separate haplotype networks for the two species, and discovered hybridization at a single locality. The two networks confirm the status of M. baroni and M. cowani as separate evolutionary species and units for conservation. Within both mitochondrial haplotype networks, specimens from different localities shared numerous identical haplotypes, even those from the most distant sample sites of M. baroni. Most populations were characterized by high haplotype diversity and no haplotype clades exclusive to geographical regions were observed. Protection of a few large populations of these species is therefore likely to conserve much of the mtDNA genetic diversity found in the entire species. While M. baroni is widespread and occurs in many nature reserves, we recommend efficient legal protection of some M. cowani habitats to protect this species against extinction.

Evidence for recent gene flow between north-eastern and south-eastern Madagascan poison frogs from a phylogeography of the Mantella cowani group

“…The hybridization mentioned in Chiari et al [23] between M. baroni and M. cowani is confirmed by our study, with a slightly shorter cytochrome b fragment but using more samples. Hybridization is a recognized phenomenon in amphibians as mentioned by numerous authors [27-29].…”

“…Our results using the cytochrome b marker confirm the results of Chiari et al [23] on the probable hybridization between M. cowani and M. baroni which, however, in general appear to be well separated species by morphology and ecology [15,23], with an uncorrected pairwise distance of about 3.5% among most of their cytochrome b haplotypes, and a clustering of these haplotypes in two unconnected networks. This distance appears to be in a similar order of magnitude as that between other closely related Mantella species, e.g., M. aurantiaca, M. crocea and M. madagascariensis (4.5–5.3%[20]).…”

“…Hence, these four individuals of M. baroni are to be considered as a posteriori hybrids (cf. definitions in [23]). The M. haraldmeieri (mh) network is separated from all other species and no indication for hybridization of this with any other species was detected.…”

“…Besides the Mantella madagascariensis and M. bernhardi groups, phylogeographic studies have also been carried out on the M. cowani group [23]. This group is likely to be monophyletic [19,20] and includes five species according to Vences et al (1999) [15]: M. cowani , which is listed in the IUCN Red List as critically endangered due to small range distribution and anthropogenic pressure [5,14,15], M. baroni and M. nigricans , both non threatened species, M. haraldmeieri , a vulnerable species from the extreme south-east, and Mantella sp.…”

“…Cytochrome b -based phylogeographic data by Chiari et al [23] were limited to two of these five species: Mantella cowani and M. baroni . Sequences of these two species formed separate haplotype networks, with haplotype sharing at one locality of their sympatric occurrence.…”