There are over 100 species of maple in the genus Acer, distributed throughout Asia, Europe and North America, with some occurring in North Africa and Malaysia. The fact that maples are largely confined to the Northern Hemisphere is a function of their evolutionary background and the pressures of the Quaternary ice age.
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Maple trees are angiosperms, or flowering plants. They originated in the Cretaceous period, sometime between 120 million and 100 million years ago. Early maples had three-lobed leaves instead of the familiar five-lobed leaves found today, and evolved into a diverse group of species including both monoecious plants, with male and female parts on a single plant, and dioecious plants, with two separate sexes. Maples reached their widest distribution in the Miocene period, between 23 million and 5 million years ago.
The oldest fossilized maple remains, from the species Acer amboyense, were found in Alaska, dated about 100 million years ago. Scientists, however, theorize that maples originated in central China, based on the distribution of other early maple fossils in Greenland, Iceland and Spitsbergen. Because there was no permanent ice cap at that point, they believe that these early trees spread over the polar region from that central point in Asia.
Ice Age Distribution
As the Earth cooled, leading into the ice age 2.58 million years ago, maple tree species were pushed further south ahead of the advancing glaciers. In Europe, where mountain ranges run east to west, the southward progress of maples was frequently blocked, resulting in localized extinction. The north-south mountain ranges of North America and the open steppes of central Asia, on the other hand, allowed maples to retreat southward from the ice unimpeded.
The taxonomic classification of maple trees has been a bit controversial over the years. Originally considered to be their own family, first named Aceraceae in 1836, the genus Acer is now lumped together with the sub-family Hippocastanaceae into a different family, Sapindaceae. This move cements the genetic relationship of maple trees with Asian tropical fruit trees like lychee and longan, along with buckeye and soapnut.