Short answers, pulled from the story.
Pollen grains found in Austrian deposits mark the oldest unequivocal records of Quercus dating to approximately 55 million years ago at the Paleocene-Eocene boundary. Scientists consider these findings definitive because macrofossils older than the Paleogene are mostly poorly preserved and lack critical features needed for certain identification.
North America hosts approximately 160 species with Mexico containing about 90 endemic varieties. China follows as the second greatest area of diversity with roughly 100 species while oaks extend from cool temperate zones to tropical latitudes across multiple continents.
Several kinds of truffles maintain symbiotic relationships with oak trees including Black Périgord truffle and white Piedmont truffle. Fungi like Ramaria flavosaponaria also associate closely with oaks to form these biological partnerships.
An estimated 31% of world oak species face extinction threats as of 2020 with China holding the highest number of threatened species at 36. Mexico follows with 32 species under conservation concern while Vietnam lists 20 threatened varieties and the US accounts for 16.
Oak timber remains strong and hard finding uses in furniture floors and building frames. Wood from Q. robur and Q. petraea was used in Europe for shipbuilding until the 19th century because naval men of war relied heavily on this durable material.