Sökning: "species trees"
Visar resultat 1 - 5 av 222 avhandlingar innehållade orden species trees.
1. Multi-trait Branching Models with Applications to Species Evolution
Sammanfattning : This thesis provides an analysis of the evolution of discrete traits and their effect on the birth and survival of species using the theory of supercritical, continuous time Markov branching processes. We present a branching modeling framework that incorporates multi-trait diversification processes associated with the emergence of new species, death of existing species, and transition of species carrying one type of a trait to another. LÄS MER
2. Phylogeny and topological incongruence in the Rubioideae (Rubiaceae)
Sammanfattning : The work with this thesis has focused on evolutionary relationships in the Rubioideae, the most species-rich subfamily of the large and diverse coffee family (Rubiaceae). Despite considerable efforts during the last decades, uncertainty regarding several relationships in this group has remained, either as a result of unconvincing statistic support, incongruent results, or insufficient taxon sampling. LÄS MER
3. Phylogenetic Relationships, Biogeography and Species Delimitation: A case study on southern African Silene (Caryophyllaceae)
Sammanfattning : The primary aim of this thesis was to explore the phylogenetic relationships and historical biogeography of African members of the plant genus Silene (Caryophyllaceae), with special focus on the eight native southern African taxa. Three loci (the nuclear ribosomal internal transcribed spacer region, and the rps16 and matK regions from the plastid genome) generated using traditional Sanger sequencing were used to infer the phylogenetic positions of African taxa, while sequence data from 28 low copy nuclear loci were generated using the target capture method to explore shallow phylogenetic relationships within southern African taxa. LÄS MER
4. Microclimate at range margins : Consequences for boreal forest understory species
Sammanfattning : A warmer climate will shift species distributional range margins poleward, but near-ground microclimates may modify these shifts. Cold-adapted northern species at their rear edge may survive locally in microrefugia with a colder microclimate, and warm-adapted southern species at their leading edge may colonize stepping stone habitats with a warmer microclimate. LÄS MER
5. Trees and the environment : Possibilities and challenges in tree-ring research across spatial and temporal scales based on case studies in Sweden
Sammanfattning : The need to understand and quantify the magnitude and frequency of past and current environmental changes increased the demand for high-resolution proxy data across spatial and temporal scales. Due to their long lifespan and global distribution, trees provide a unique and continuous record of environmental variability. LÄS MER