Showing papers on "Mantella published in 2008"

Individual and Geographic Variation of Skin Alkaloids in Three Species of Madagascan Poison Frogs (Mantella)

Abstract: Alkaloid profiles for 81 individual mantellid frogs, Mantella baroni (Boulenger 1988) (N = 19), M. bernhardi (N = 51), and M. madagascariensis (Grandidier 1877) (N = 11), from six different populations from Madagascar were examined. Marked individual differences in alkaloid composition (number, type, and amount) were observed between different species and between populations of the same species. Disjunct populations of each of the three species differed significantly in alkaloid composition. Sympatric populations of M. baroni and M. madagascariensis also differed significantly in alkaloid composition. In M. bernhardi, differences in alkaloid composition were marginally associated with different sexes. A total of 111 alkaloids, including isomers, were detected in analysis of the individuals from the three species. The majority (47%) appear likely to be obtained from dietary mites, whereas many of the others (18%) are presumed to be from ants, and a few (4%) are from millipedes. Putative dietary sources for the remaining alkaloids are generally unknown, but beetles are probably the source of at least some of the tricyclic alkaloids (6%). In addition, alkaloid compositions from extracts of groups of individuals from five additional populations of M. baroni and from one population of M. bernhardi (Vences et al. 1994) and one population of M. cowanii (Boulenger 1882) were examined. An additional 50 alkaloids, including isomers, were detected in the combined samples, bringing the total number of alkaloids identified from these four species of mantellid frogs to 161. Alkaloid compositions in mantellid poison frogs are diverse and highly dependent on geographic location that appear to be largely determined by the nature and availability of alkaloid-containing prey items.

Update of the Global Amphibian Assessment for Madagascar in light of species discoveries, nomenclature changes, and new field information

Abstract: We updated the Global Amphibian Assessment for Malagasy amphibians, including considerations on the species described or resurrected between 2005-2007, and newly available information on other taxa. The revised assessment allowed us to include 66 threatened species: 6 Critically Endangered, 31 Endangered, and 29 Vulnerable. Three species formerly assessed as Critically Endangered (Mantella expectata, M. viridis, and Scaphiophryne gottlebei) are downlisted to Endangered, since they are more widespread than formerly presumed. Other recently described species have been assessed as threatened: seven are categorised as Endangered (Boophis tampoka, Gephyromantis azzurrae, G. runewsweeki, Mantidactylus noralottae, Tsingymantis antitra, Cophyla berara, and Plethodontohyla fonetana), and a single species (Boophis sambirano) categorised as Vulnerable. The little known and enigmatic Mantella manery, formerly assessed as Data Deficient, has been recently found on the Tsaratanana Massif. In view of this enlarged distribution and ongoing degradation of the habitats where it lives, it has been re-assessed as Vulnerable.

The amphibians of Isalo Massif, southern-central Madagascar: high frog diversity in an apparently hostile dry habitat

Abstract: We provide a list of the amphibians from the Isalo Massif, southern-central Madagascar, with data on their ecology and acoustics. Although this area is constituted by a xeric sandstone massif crossed by canyons and extended savannah-like grasslands, the number of discovered frog species turned out to be high (21). This is the highest number of amphibian species ever found at a western locality of Madagascar. The number of species known to be endemic from this area is at least five (Mantella expectata, Gephyromantis azzurrae, G. corvus, Mantidactylus noralottae ,a nd Scaphiophryne gottlebei), with some other taxa (Boophis occidentalis, B. cf. periegetes, Mantidactylus sp. aff. ulcerosus), that are possibly Isalo-endemic too. This high endemicity level indicates the refuge effect played by the massif during repeated climatic changes, and the specialisation of these species to the peculiar canyon-habitat. Two sympatric species of Gephyromantis (G. azzurrae and G. corvus) evolved independently, likely for adaptation to two different aspects of the canyons (narrow or open). Part of the massif is currently managed as a national park, which is the most visited protected area of Madagascar. The remaining part of the massif is still unprotected and is threatened by the repeated fires and by the ongoing exploitation for sapphire mining. Two species, Mantella expectata and Scaphiophryne gottlebei, are captured for pet-trade, and considerations are provided regarding their conservation status.

Geographical distribution of three species of Malagasy poison frogs of high conservation priority: Mantella aurantiaca, M. crocea and M. milotympanum

Abstract: The genus Mantella comprises 16 described species of Malagasy poison frogs, several of which are threatened. Despite their importance as flagship species for conservation, remarkably little was known until recently about their geographical distribution. We here provide a revision of the distribution of a complex of three closely related Mantella species from central eastern Madagascar: Mantella aurantiaca (Critically Endangered) M. crocea (Endangered) and M. milotympanum (Critically Endangered). These taxa were thus far known from only a very limited number of sites. Based on own surveys, we could identify 21 new sites to complement the 13 sites known for these frogs. We also provide corrected geographical coordinates for some published sites. Altogether 16 localities are known for M. aurantiaca, nine for M. crocea, five for M. cf milotympanum and four for M. milotympanum. One site of M. crocea is in a Special Reserve (Ambohitantely), a second possibly in the Zahamena National Park, one site of M. aurantiaca (Torotorofotsy) is protected as Ramsar site, and a second site of M. aurantiaca is at the boundary of, and possibly inside, Mantadia National Park, but all other localities do not receive legal protection. All newly recorded sites are along the western edge of the eastern forest band, except Ambohitantely which is a relict forest in central Madagascar. Among the sites reported for M. aurantiaca, only one (Ambakoana) is situated on the western bank of the Mangoro River, indicating that this river is no insurmountable barrier for this species, at least in its upper course.

New distribution data of the green mantella, Mantella viridis, from northern Madagascar (Anura: Mantellidae)

Abstract: Mantellas are colourful small frogs endemic from Madagascar. Although data on their distribution are being accumulated, for some species only little information is available, fact influencing their conservation management. Therefore, we conducted a field work in the Antsiranana region aimed to unveil the distribution of Mantella viridis. Of the 42 visited sites, 32 (76%) were confirmed with the presence of the species and ten other sites (31%) with the presence of M. ebenaui or a different form intermediate in colouration between M. viridis and M. ebenaui. M. viridis was found in different primary and secondary habitats. This adaptability allows the colonization degraded habitats as well as human perturbed areas. Thus, seen both the new emerged geographic scenario, and the ecological plasticity the conservation status of this species needs to be re-evaluated.

Rapid assessments of population sizes in ten species of Malagasy poison frogs, genus Mantella

Abstract: Among the amphibians of Madagascar, the Malagasy poison frogs of the genus Mantella are the group that is most heavily collected for the pet trade. Although the taxonomy and genetic diversity of these frogs has been intensively studied in the past, very few data on their population dynamics are available, although such data are badly needed to evaluate and regulate their commercial collecting and export. Here we summarize available population density data on Malagasy poison frogs and report on own data based on rapid mark-recapture population estimates of ten Mantella species, carried out between 2003-2007. Population sizes usually were around 50-200 individuals, but these data must be seen as preliminary because they refer to specimens at particular reproduction sites (in swamps or along streams), and in some cases are heavily biased towards males since females were more difficult to collect. These partly very high population densities in our and previous studies refer to specimens gathering in very small areas (down to 50 square meters in Mantella viridis where the highest densities were recorded) and therefore can by no means be extrapolated to the whole distribution areas of these species. Long-term studies of the dynamics of particular populations, home ranges and dispersal, and of longevity and recruitment, need to be combined with such short-term density estimates to understand the perspectives of sustainable harvesting of Malagasy poison frogs.