The Tulip Tree and its fossil genome

Many tree species such as Hemlock (Tsuga), Sweet Gum (Liquid Amber), Magnolia and Tulip trees went extinct in Europe during the Pleistocene yet managed to survive the ice ages in North America and Asia. Their extinction is attributed to overall harsher climates through Europe, being closer to the ocean as well as zonal mountain ranges (i.e. the Pyrenees) that halted southerly migrations from the colder north. The larger continentality of the United States and north-to-south aspect of ranges was kinder to tree species during glacial phases.

Isolated relict populations do survive today such as Liquid Amber in Rhodes and Zelkova Abelica (Elm) in Crete and Sicily. 

Today and in the future, the genetic study of plants is and will continue to unravel valuable new information regarding plant evolution and distributions.

The Tulip Tree (Liriodendron tulipifera) in Eastern North America, related to the Magnolia (Magnoliaceae) family that disappeared in Europe due to the competition from more robust and faster growing tree species during the last 2 million years although today 26 magnolia species are found in North America and 80 in S.E. Asia.

 The Tulip Tree (Liriodendron tulipifera)

Interestingly in 2013, research groups from Indiana and Arkansas Universities determined that genetic material within the Tulip tree has remained largely unchanged since the time of the dinosaurs, making it a valuable archive of many genes lost during 200 million years of angiosperm evolution.  Jeffrey Palmer, coauthor of the study explained that due to the slow silent mutation rate, the genome appeared to have been frozen in time for millions of years Richardson (2013).  Prof. Ian Small of the University of Western Australia explained in commentary to the above article that Liriodendron belonged to an early lineage branch that is distinct from other groups to which most of the world's crops belong.

The Tulip Tree survived in North America through mega-scale Cenzoic cooling from greenhouse to icehouse conditions, major continental tectonic changes, orbital and millennial scale climate variability. 

It is also the state tree of Indiana, Kentucky and Tennessee.