"Conservation genetics" von Amphibien Madagaskars

Conservation genetics is a relatively newly recognized subdiscipline of conservation biology and aims to minimize the risk of decline or extinction due to genetic factors. This subdiscipline is lately growing really fast, according to the publications of text books on this topic and the creation of a new journal specific for the field.In this thesis I present the work of three years of Ph.D. research on conservation genetics of Malagasy amphibians. The aim of this thesis was to start a genetic survey of species of frogs for which other data on distribution and, in particular, restriction to primary forest habitat were available (Vences et al. 1999). The importance of the chapters presented in this thesis is that they represent the first studies on genetic variability within species and species groups done on a group (Anura) with incredibly high level of endemism in Madagascar, one of the richest hotspot for biodiversity conservation of the world. On the island, habitat destruction such as deforestation with the practice of slash-and-burn agriculture and heavy anthropogenic pressure negatively affect amphibian survivorship and distribution. In particular cophyline microhylids and some clades of mantellids are sensitive to forest fragmentation and loss of habitat. Additionally some colourful species of the genera Mantella, Dyscophus and Scaphiophryne are exported in high numbers for the pet trade.My research includes constructing robust phylogenies (Chapters 2 and 7), resolving the taxonomic uncertainties (Chapter 5), identifying genetic units for conservation (Chapters 2, 3, 4 and 5), resolving the extent of gene flow among populations (Chapters 1, 2, 3, 4 and 5), correlating genetic variability and ecology (Chapter 2) and study the utility of commonly used mitochondrial and nuclear genetic markers (Chapters 6, 7 and 8). The work I present here represents the first data collected at the population level on Malagasy frogs. My research involves the Mantella madagascariensis, M. cowani and M. bernhardi species groups and Dyscophus antongilii and guineti (all on CITES appendices I and II, except D. guineti), of which mitochondrial and nuclear sequences and microsatellite data were assembled. Among the species analyzed in my work, the genus Mantella is particularly interesting from an evolutionary point of view also for its variation in coloration (analyzed and presented in Chapter 2), for the presence of toxins in the skin and for a peculiar reproductive behaviour (shared with the genus Mantidactylus). Moreover, the clarification of taxonomic uncertainties and the identification of conservation units directly contribute to conservation efforts and establishment of export quotas, and will be helpful in defining possible strategies of sustainable use of these frogs.As my Ph.D. work is the first one into population and conservation genetics of Malagasy amphibians, further studies should be focused on the analyses of the genetic variability within and among the other species of Malagasy frogs, combining both mitochondrial and nuclear data. This kind of study should be carrying out also on other species and other vertebrate groups with different dispersal capacity and biology.In Chapter 1, the genus Mantella is studied from a phylogenetic and population genetic point of view. In Chapter 2, the work presented in Chapter 1 has been extended to more populations and more individuals within the genus Mantella. Individuals with intermediate coloration have also been included and the evolution of coloration was studied in this chapter with more attention to the M. madagascariensis group.Chapters 3 and 4 are focused on a population genetic analysis of two other species group within the genus Mantella, the M. cowani (Chapter 3) and M. bernhardi (Chapter 4) species groups. Chapter 3 shows the results on the degree and distribution of the genetic variation and phylogeography of two species of the Mantella cowani species group, M. cowani and M. baroni.In Chapter 5 the importance of resolving taxonomic uncertainties for conservation measures is analyzed through the case of Dyscophus antongilii and D. guineti. D. antongilii is currently included in Appendix I of CITES and its exportation is banned completely, while D. guineti does not receive any legal protection and it is regularly exported.Chapters 6, 7 and 8 show the results on the study on the performance of different mitochondrial and nuclear markers to be used to answer different biological questions