Evolution of Marsupial Genomes

Marsupial genomes, which are packaged into large chromosomes, provide a powerful resource for studying the mechanisms of genome evolution. The extensive and valuable body of work on marsupial cytogenetics, combined more recently with genome sequence data, has enabled prediction of the 2 n = 14 karyotype ancestral to all marsupial families. The application of both chromosome biology and genome sequencing, or chromosomics, has been a necessary approach for various aspects of mammalian genome evolution, such as understanding sex chromosome evolution and the origin and evolution of transmissible tumors in Tasmanian devils. The next phase of marsupial genome evolution research will employ chromosomics approaches to begin addressing fundamental questions in marsupial genome evolution and chromosome evolution more generally. The answers to these complex questions will impact our understanding across a broad range of fields, including the genetics of speciation, genome adaptation to environmental stressors, and species management.

Patterns, Mechanisms and Genetics of Speciation in Reptiles and Amphibians

In this contribution, the aspects of reptile and amphibian speciation that emerged from research performed over the past decade are reviewed. First, this study assesses how patterns and processes of speciation depend on knowing the taxonomy of the group in question, and discuss how integrative taxonomy has contributed to speciation research in these groups. This study then reviews the research on different aspects of speciation in reptiles and amphibians, including biogeography and climatic niches, ecological speciation, the relationship between speciation rates and phenotypic traits, and genetics and genomics. Further, several case studies of speciation in reptiles and amphibians that exemplify many of these themes are discussed. These include studies of integrative taxonomy and biogeography in South American lizards, ecological speciation in European salamanders, speciation and phenotypic evolution in frogs and lizards. The final case study combines genomics and biogeography in tortoises. The field of amphibian and reptile speciation research has steadily moved forward from the assessment of geographic and ecological aspects, to incorporating other dimensions of speciation, such as genetic mechanisms and evolutionary forces. A higher degree of integration among all these dimensions emerges as a goal for future research.