56 research outputs found
Flammable biomes dominated by eucalypts originated at the Cretaceous-Palaeogene boundary
Fire is a major modifier of communities, but the evolutionary origins of its prevalent role in shaping current biomes are uncertain. Australia is among the most fire-prone continents, with most of the landmass occupied by the fire-dependent sclerophyll and savanna biomes. In contrast to biomes with similar climates in other continents, Australia has a tree flora dominated by a single genus, Eucalyptus, and related Myrtaceae. A unique mechanism in Myrtaceae for enduring and recovering from fire damage likely resulted in this dominance. Here, we find a conserved phylogenetic relationship between post-fire resprouting (epicormic) anatomy and biome evolution, dating from 60 to 62 Ma, in the earliest Palaeogene. Thus, fire-dependent communities likely existed 50 million years earlier than previously thought. We predict that epicormic resprouting could make eucalypt forests and woodlands an excellent long-term carbon bank for reducing atmospheric CO2 compared with biomes with similar fire regimes in other continents
Chloroplast DNA from lettuce and Barnadesia (Asteraceae): structure, gene localization, and characterization of a large inversion
We have cloned into plasmids 17 of 18 lettuce chloroplast DNA SacI fragments covering 96% of the genome. The cloned fragments were used to construct cleavage maps for 10 restriction enzymes for the chloroplast genomes of lettuce ( Lactuca sativa ) and Barnadesia caryophylla , two distantly related species in the sunflower family (Asteraceae). Both genomes are approximately 151 kb in size and contain a 25 kb inverted repeat. We also mapped the position and orientation of 37 chloroplast DNA genes. The mapping studies reveal that chloroplast DNAs of lettuce and Barnadesia differ by a 22 kb inversion in the large single copy region. Barnadesia has retained the primitive land plant genome arrangement, while the inversion has occurred in a lettuce lineage. The endpoints of the derived lettuce inversion were located by comparison to the well-characterized spinach and tobacco genomes. Both endpoints are located in intergenic spacers within tRNA gene clusters; one cluster being located downstream from the atpA gene and the other upstream from the psbD gene. The endpoint near the atpA gene is very close to one endpoint of a 20 kb inversion in wheat (Howe et al. 1983; Quigley and Weil 1985). Comparison of the restriction site maps gives an estimated sequence divergence of 3.7% for the lettuce and Barnadesia genomes. This value is relatively low compared to previous estimates for other angiosperm groups, suggesting a high degree of sequence conservation in the Asteraceae.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46961/1/294_2004_Article_BF00384619.pd
Trichomes that secrete substances of a mixed nature in the vegetative and reproductive organs of some species of Moraceae
Chloroplast DNA variability in the genus Helianthus: restriction analysis and S1 nuclease mapping of DNA-DNA heteroduplexes
Species relationships in the Hordeum murinum aggregate viewed from chloroplast DNA restriction fragment patterns
Character-State Weighting for Restriction Site Data in Phylogenetic Reconstruction, with an Example from Chloroplast DNA
Chloroplast DNA Restriction Site Variation and the Evolution of the Annual Habit in North American Coreopsis (Asteraceae)
- …