https://www.selleckchem.com/products/apx-115-free-base.html When three taxa co-occur, the pattern is two diploids from different clades and a tetraploid. Field and herbarium data both indicate flowering phenology is displaced between diploids from the two clades; one of the diploid clades and tetraploids overlap considerably. The two deep clades in Arctostaphylos are genetically distant, with hybrids rare or non-existent when taxa co-occur. Reproductive isolation between clades is enhanced by displaced flowering phenology for co-occurring species. Within clades, taxa appear to have few reproductive barriers other than an allopatric distribution or different ploidy levels. The two deep clades in Arctostaphylos are genetically distant, with hybrids rare or non-existent when taxa co-occur. Reproductive isolation between clades is enhanced by displaced flowering phenology for co-occurring species. Within clades, taxa appear to have few reproductive barriers other than an allopatric distribution or different ploidy levels. Fossils provide fundamental evidence of the evolutionary processes that crafted today's biodiversity and consequently for understanding life on Earth. We report the finding of Myrtaceidites eucalyptoides pollen grains preserved within the anthers of a 52-million-year-old Eucalyptus flower collected at Laguna del Hunco locality of Argentinean Patagonia and discuss its implications in understanding the evolutionary history of the iconic Australian genus Eucalyptus. Pollen grains were extracted from the flower's anthers and were then observed under light microscopy and scanning electron microscopy. The phylogenetic position of the fossil was investigated by adding pollen data to a previously published total-evidence matrix and analyzing it using parsimony. We erect the species Eucalyptus xoshemium for the fossil flower. Pollen extracted from E. xoshemium belongs to the species Myrtaceidites eucalyptoides, which, until now, was only known as dispersed poll